diff --git a/commandsu.pas b/commandsu.pas
index 1326b58..5a2e03f 100755
--- a/commandsu.pas
+++ b/commandsu.pas
@@ -53,6 +53,7 @@ procedure OVERLAYMINMAX (lOverlay: integer; lMin,lMax: single);
 procedure OVERLAYTRANSPARENCYONBACKGROUND(lPct: integer);
 procedure OVERLAYVISIBLE(lOverlay: integer; VISIBLE: boolean);
 procedure OVERLAYTRANSLUCENT(lOverlay: integer; TRANSLUCENT: boolean);
+procedure OVERLAYOPACITY(lOverlay: integer; OPACITY: byte);
 procedure OVERLAYINVERT(lOverlay: integer; INVERT: boolean);
 procedure OVERLAYSMOOTHVOXELWISEDATA (SMOOTH: boolean);
 procedure QUIT;
@@ -87,7 +88,7 @@ procedure WAIT (MSEC: integer);
                (Ptr:@VERSION;Decl:'VERSION';Vars:'(): string')
              );
 
-knProc = 67;
+knProc = 68;
   kProcRA : array [1..knProc] of TScriptRec = (
   (Ptr:@ATLASSTATMAP;Decl:'ATLASSTATMAP';Vars:'(ATLASNAME, STATNAME: string; const Intensities: array of integer; const Intensities: array of single)'),
   (Ptr:@ATLASSATURATIONALPHA;Decl:'ATLASSATURATIONALPHA';Vars:'(lSaturation, lTransparency: single)'),
@@ -133,6 +134,7 @@ procedure WAIT (MSEC: integer);
    (Ptr:@OVERLAYCOLORNAME;Decl:'OVERLAYCOLORNAME';Vars:'(lOverlay: integer; lFilename: string)'),
    (Ptr:@OVERLAYLOAD;Decl:'OVERLAYLOAD';Vars:'(lFilename: string)'),
    (Ptr:@OVERLAYMINMAX;Decl:'OVERLAYMINMAX';Vars:'(lOverlay: integer; lMin,lMax: single)'),
+   (Ptr:@OVERLAYOPACITY;Decl:'OVERLAYOPACITY';Vars:'(lOverlay: integer; OPACITY: byte)'),
    (Ptr:@OVERLAYTRANSPARENCYONBACKGROUND;Decl:'OVERLAYTRANSPARENCYONBACKGROUND';Vars:'(lPct: integer)'),
    (Ptr:@OVERLAYVISIBLE;Decl:'OVERLAYVISIBLE';Vars:'(lOverlay: integer; VISIBLE: boolean)'),
    (Ptr:@OVERLAYTRANSLUCENT;Decl:'OVERLAYTRANSLUCENT';Vars:'(lOverlay: integer; TRANSLUCENT: boolean)'),
@@ -862,6 +864,14 @@ procedure OVERLAYTRANSLUCENT(lOverlay: integer; TRANSLUCENT: boolean);
      else
          GLForm1.OverlayVisible(lOverlay, kLUTopaque);
 end;
+
+procedure OVERLAYOPACITY(lOverlay: integer; OPACITY: byte);
+begin
+     if OPACITY > 100 then
+        OPACITY := 100;
+     GLForm1.OverlayVisible(lOverlay, OPACITY);
+end;
+
 procedure OVERLAYVISIBLE(lOverlay: integer; VISIBLE: boolean);
 begin
      if VISIBLE then
diff --git a/mainunit.lfm b/mainunit.lfm
index 9d5a33f..c5848dd 100755
--- a/mainunit.lfm
+++ b/mainunit.lfm
@@ -2189,47 +2189,48 @@ object GLForm1: TGLForm1
             Hint = 'overlaycloseall () This function has no parameters. All open overlays will be closed.'
             OnClick = InsertCommand
           end
+          object overlaycolorfromzero1: TMenuItem
+            Tag = 1
+            Caption = 'overlaycolorfromzero'
+            Hint = 'overlaycolorfromzero (fromzero: boolean) If set to false, then the full color range is used to show the overlay.'
+            Visible = False
+            OnClick = InsertCommand
+          end
           object overlaycolorname1: TMenuItem
             Tag = 1214
             Caption = 'overlaycolorname'
             Hint = 'overlaycolorname (overlay: integer; filename: string) Set the colorscheme for the target overlay to a specified name.'
             OnClick = InsertCommand
           end
+          object overlayinvert1: TMenuItem
+            Tag = 1211
+            Caption = 'overlayinvert'
+            Hint = 'overlayinvert (overlay: integer; invert: boolean) toggle whether overlay color scheme is inverted.'
+            OnClick = InsertCommand
+          end
           object overlayminmax1: TMenuItem
             Tag = 1223
             Caption = 'overlayminmax'
             Hint = 'overlayminmax (overlay: integer; min, max: float) Sets the color range for the overlay.'
             OnClick = InsertCommand
           end
-          object overlaytransparencyonbackground1: TMenuItem
-            Tag = 2
-            Caption = 'overlaytransparencyonbackground'
-            Hint = 'overlaytransparencyonbackground (percent: integer) Controls the opacity of the overlays on the background.'
-            OnClick = InsertCommand
-          end
-          object overlaycolorfromzero1: TMenuItem
-            Tag = 1
-            Caption = 'overlaycolorfromzero'
-            Hint = 'overlaycolorfromzero (fromzero: boolean) If set to false, then the full color range is used to show the overlay.'
-            Visible = False
-            OnClick = InsertCommand
-          end
-          object overlayvisible1: TMenuItem
-            Tag = 1211
-            Caption = 'overlayvisible'
-            Hint = 'overlayvisible (overlay: integer; visible: boolean) This feature allows you to make individual overlays visible or invisible.'
+          object overlayopacity1: TMenuItem
+            Tag = 22
+            Caption = 'overlayopacity'
+            Hint = 'overlayopacity (overlay, opacity: integer) This feature allows you to make individual overlays range from transparent (0) to opaque (100).'
             OnClick = InsertCommand
           end
           object overlaytranslucent1: TMenuItem
             Tag = 1211
             Caption = 'overlaytranslucent'
             Hint = 'overlaytranslucent (overlay: integer; translucent: boolean) This feature allows you to make individual overlays translucent or opaque.'
+            Visible = False
             OnClick = InsertCommand
           end
-          object overlayinvert1: TMenuItem
+          object overlayvisible1: TMenuItem
             Tag = 1211
-            Caption = 'overlayinvert'
-            Hint = 'overlayinvert (overlay: integer; invert: boolean) toggle whether overlay color scheme is inverted.'
+            Caption = 'overlayvisible'
+            Hint = 'overlayvisible (overlay: integer; visible: boolean) This feature allows you to make individual overlays visible or invisible.'
             OnClick = InsertCommand
           end
           object overlaysmoothvoxelwisedata1: TMenuItem
@@ -2238,6 +2239,12 @@ object GLForm1: TGLForm1
             Hint = 'overlaysmoothvoxelwisedata (smooth: boolean) Determines if overlays are loaded using interpolation (smooth) or nearest neighbor (un-smoothed) interpolation.'
             OnClick = InsertCommand
           end
+          object overlaytransparencyonbackground1: TMenuItem
+            Tag = 2
+            Caption = 'overlaytransparencyonbackground'
+            Hint = 'overlaytransparencyonbackground (percent: integer) Controls the opacity of the overlays on the background.'
+            OnClick = InsertCommand
+          end
           object meshoverlayorder1: TMenuItem
             Tag = 1
             Caption = 'meshoverlayorder'
diff --git a/mainunit.pas b/mainunit.pas
index b7bff04..6ae3435 100755
--- a/mainunit.pas
+++ b/mainunit.pas
@@ -33,6 +33,7 @@   TGLForm1 = class(TForm)
  CenterPanel: TPanel;
  LayerAOMapMenu: TMenuItem;
  LayerPainHideMenu: TMenuItem;
+ overlayopacity1: TMenuItem;
  PaintModeAutomatic: TMenuItem;
  PaintModeHideBrightHideDarkMenu: TMenuItem;
  PaintModeHideDarkShowBrightMenu: TMenuItem;
@@ -1100,6 +1101,16 @@ function PyOVERLAYTRANSLUCENT(Self, Args : PPyObject): PPyObject; cdecl;
       OVERLAYTRANSLUCENT(I,Bool(B));
 end;
 
+function PyOVERLAYOPACITY(Self, Args : PPyObject): PPyObject; cdecl;
+var
+  B,I: integer;
+begin
+  Result:= GetPythonEngine.PyBool_FromLong(Ord(True));
+  with GetPythonEngine do
+    if Bool(PyArg_ParseTuple(Args, 'ii:overlaytranslucent', @I,@B)) then
+      OVERLAYOPACITY(I,B);
+end;
+
 function PyEDGETHRESH(Self, Args : PPyObject): PPyObject; cdecl;
 var
   A,B: single;
@@ -1647,6 +1658,7 @@ procedure TGLForm1.PyModInitialization(Sender: TObject);
     AddMethod('overlayinvert', @PyOVERLAYINVERT, ' overlayinvert(overlaLayer, invert) -> Toggle whether overlay color scheme is inverted.');
     AddMethod('overlayload', @PyOVERLAYLOAD, ' overlayload(filename) -> Load an image on top of prior images.');
     AddMethod('overlayminmax', @PyOVERLAYMINMAX, ' overlayminmax(layer, min, max) -> Sets the color range for the overlay (layer 0 = background).');
+    AddMethod('overlayopacity', @PyOVERLAYOPACITY, ' overlayopacity(overlayLayer, opacity) -> This feature allows you to adjust individual overlays transparency from transparent (0) to opaque (100).');
     AddMethod('overlaysmoothvoxelwisedata', @PyOVERLAYSMOOTHVOXELWISEDATA, ' overlaysmoothvoxelwisedata(smooth) -> Determines if overlays are loaded using interpolation (smooth, 1) or nearest neighbor (un-smoothed, 0) interpolation.');
     AddMethod('overlaytranslucent', @PyOVERLAYTRANSLUCENT, ' overlaytranslucent(overlayLayer, translucent) -> This feature allows you to make individual overlays translucent or opaque.');
     AddMethod('overlaytransparencyonbackground', @PyOVERLAYTRANSPARENCYONBACKGROUND, ' overlaytransparencyonbackground(percent) -> Controls the opacity of the overlays on the background.');
@@ -2633,6 +2645,45 @@ function isVtkMesh (filename: string): boolean; //vtk files can be tracks (" LIN
      if (pos('TRIANGLE_STRIPS ', Str) > 0) then result := true; //faces
 end;
 
+function isVtkTrack (filename: string): boolean; //vtk files can be volumes(DATASET STRUCTURED_POINTS) tracks (" LINES" ->Tracks/Open) or meshes ("POLYGONS " -> File/Open, Overlay/Open)
+var
+      f: file;
+      Str: string;
+      szRead: integer;
+begin
+     result := false;
+     if not fileexistsF(filename) then exit;
+     FileMode := fmOpenRead;
+     AssignFile(f, FileName);
+     Reset(f,1);
+     FileMode := fmOpenRead;
+     szRead := FileSize(f);
+     SetLength(Str, szRead);
+     BlockRead(f, Str[1],szRead);
+     CloseFile(f);
+     if (pos('POINTS ', Str) > 0)and (pos('LINES ', Str) > 0) then result := true; //faces
+end;
+
+
+function isVtkVolume (filename: string): boolean; //vtk files can be volumes(DATASET STRUCTURED_POINTS) tracks (" LINES" ->Tracks/Open) or meshes ("POLYGONS " -> File/Open, Overlay/Open)
+var
+      f: file;
+      Str: string;
+      szRead: integer;
+begin
+     result := false;
+     if not fileexistsF(filename) then exit;
+     FileMode := fmOpenRead;
+     AssignFile(f, FileName);
+     Reset(f,1);
+     FileMode := fmOpenRead;
+     szRead := FileSize(f);
+     SetLength(Str, szRead);
+     BlockRead(f, Str[1],szRead);
+     CloseFile(f);
+     if ((pos('STRUCTURED_POINTS', Str) > 0) and (pos('POINT_DATA ', Str) > 0)) then result := true;
+end;
+
 function isGiiMesh (filename: string): boolean;
 //returns true if file is a valid mesh (faces+vertices), returns false if overlay map
 var
@@ -2717,9 +2768,12 @@ function TGLForm1.OpenMesh(FilenameIN: string): boolean;
   if (ext2 = '.1D.DSET') or (ext = '.COL') or (ext = '.ANNOT') or (ext = '.MGH') or (ext = '.MGZ')  or (ext = '.NII') or (ext = '.HDR')  or (ext = '.NII.GZ') or (ext = '.DPV') or (ext = '.ANNOT') or (ext = '.W') or (ext = '.CURV')  then begin
     OpenOverlay(Filename);
     exit;
-  end else if (ext = '.VTK') and (not isVtkMesh (Filename)) then begin
+  end else if (ext = '.VTK') and (isVtkTrack (Filename)) then begin
     OpenTrack(Filename);  //.vtk files can be either meshes or tracks - autodetect
     exit;
+  end else if (ext = '.VTK') and (length(gMesh.Faces) > 0) and (isVtkVolume (Filename))then begin
+    OpenOverlay(Filename);  //.vtk files can be either meshes or tracks - autodetect
+    exit;
   end else if (length(gMesh.Faces) > 0) and (ext = '.MZ3') and (not isMz3Mesh (Filename)) then begin
     OpenOverlay(Filename);  //GIfTI files can be meshes or overlays - autodetect
     exit;
diff --git a/mesh.pas b/mesh.pas
index 2b466f6..4a1b19a 100755
--- a/mesh.pas
+++ b/mesh.pas
@@ -1698,7 +1698,7 @@ function i32(): uint32;
   FileMode := fmOpenRead;
   AssignFile(f, FileName);
   Reset(f,1);
-  ReadLnBin(f, str); //signature: '# vtk DataFile'
+  ReadLnBin(f, str); //signature
   if (not AnsiContainsText(str, 'OFF')) or (not AnsiContainsText(str, 'BINARY')) then begin
     showmessage('Does not appear to be a OFF BINARY file.');
     goto 666;
@@ -6388,14 +6388,27 @@ function TMesh.LoadIdtf(const FileName: string): boolean;
     CloseFile(f);
 end; //LoaIdtfTxt()
 
+function ReadLnVtk(var f: TextFile; out str: string): boolean;
+begin
+     str := '';
+     while (str = '') or (str = ' ') do begin
+           if EOF(f) then exit(false);
+           Readln(f,str);
+     end;
+     result := true;
+end;
+
 function TMesh.LoadVtkTxt(const FileName: string): boolean;
 label
    666;
+const
+  kBlockSz = 4096;
 var
   f: TextFile;
   str: string;
   strlst: TStringList;
-  num_v, num_f, i, n, nMax: integer;
+  num_v, num_f, i, n, sz, nx, num_fx: integer;
+  face: TPoint3i;
 begin
     result := false;
     if (FSize(FileName) < 64) then exit;
@@ -6414,7 +6427,7 @@ function TMesh.LoadVtkTxt(const FileName: string): boolean;
        showmessage('Use LoadVtk() to read binary files');
        goto 666;
     end else if pos('ASCII', UpperCase(str)) = 0 then begin
-       showmessage('VTK data should be ASCII or BINARY, not '+str);
+       showmessage('VTK data should be ASCII or BINARY, not "'+str+'"');
        goto 666;
     end;
     ReadLn(f, str); // kind, e.g. "DATASET POLYDATA" or "DATASET STRUCTURED_ POINTS"
@@ -6439,28 +6452,50 @@ function TMesh.LoadVtkTxt(const FileName: string): boolean;
       goto 666;
     end;
     setlength(vertices, num_v);
-    for i := 0 to (num_v-1) do
-        Readln(f,vertices[i].X, vertices[i].Y, vertices[i].Z);
-    Readln(f,str);
+    for i := 0 to (num_v-1) do begin
+        //see Honolulu.vtk where 6 vertices are saved on each line! https://vtk.org/vtk-textbook-examples-and-data/
+           //Readln(f,vertices[i].X, vertices[i].Y, vertices[i].Z);
+           Read(f,vertices[i].X, vertices[i].Y, vertices[i].Z);
+    end;
+    ReadLnVtk(f,str);
     if pos('POLYGONS', UpperCase(str)) <> 1 then begin
-       showmessage('Expected header to report "POLYGONS" (hint: binary reader can read more variations) '+ str);
+       showmessage('Expected header to report "POLYGONS" (hint: open with Slicer and save as conventional format) "'+ str+'"');
        goto 666;
     end;
     strlst.DelimitedText := str;
     num_f := StrToIntDef(strlst[1],0);
+    sz := StrToIntDef(strlst[2],0);
     //showmessage(inttostr());
     if (num_f < 1) then begin
        showmessage('Expected at least 1 polygon not '+ str);
        goto 666;
     end;
     setlength(faces, num_f);
-    nMax := 0;
-    for i := 0 to (num_f-1) do begin
-        Readln(f,n,faces[i].X, faces[i].Y, faces[i].Z);
-        if n > nMax then nMax := n;
+    if (sz = (num_f * 4)) then begin //special case: all triangles
+      //unlike binary data, there is virtually no benefit in detecting triangular ASCII data
+      for i := 0 to (num_f-1) do begin
+          Readln(f,n,faces[i].X, faces[i].Y, faces[i].Z);
+          if n <> 3 then goto 666; //not all triangles
+      end;
+    end else begin //if all triangles else some ngons
+      num_fx := 0;
+      for i := 0 to (num_f-1) do begin
+          Read(f,n,face.X, face.Y);
+          if n < 3 then goto 666; //minimum n-gon is a triangle
+          nx := n - 2; //e.g. if "3", one triangle, if "4" then quad = 2 triangles
+          if (num_fx + nx) > length(faces) then
+             setlength(faces, num_fx+nx+kBlockSz);
+          for n := 1 to nx do begin
+              Read(f, face.Z);
+              faces[num_fx] := face;
+              //face.X := face.Y;
+              face.Y := face.Z;
+              num_fx := num_fx + 1;
+          end;
+          //num_fx := num_fx + nx; //e.g.
+      end;
+      setlength(faces, num_fx);
     end;
-    if nMax > 3 then
-       showmessage('Warning: expected a mesh of triangles.');
     result := true;
   666:
     if not result then begin
@@ -6471,6 +6506,297 @@ function TMesh.LoadVtkTxt(const FileName: string): boolean;
     CloseFile(f);
 end; //LoadVtkTxt()
 
+function ReadLnBinVTK(var f: TFByte; var s: string; skipEmptyLines: boolean = true): boolean;
+const
+  kEOLN = $0A;
+  kCR = $0D;
+var
+   bt : Byte;
+begin
+     s := '';
+     if EOF(f) then exit(false);
+     while (not  EOF(f)) do begin
+           Read(f,bt);
+           if (bt = kCR) then continue;
+           if (bt = kEOLN) and ((not skipEmptyLines) or (s <> '' )) then exit(true);
+           if (bt = kEOLN) then continue;
+           s := s + Chr(bt);
+     end;
+     exit(true);
+end;
+
+{$DEFINE NEWVTK}
+{$IFDEF NEWVTK}
+procedure TMesh.LoadVtk(const FileName: string);
+//Read VTK mesh
+// https://github.com/bonilhamusclab/MRIcroS/blob/master/%2BfileUtils/%2Bvtk/readVtk.m
+// http://www.ifb.ethz.ch/education/statisticalphysics/file-formats.pdf
+// ftp://ftp.tuwien.ac.at/visual/vtk/www/FileFormats.pdf
+//  "The VTK data files described here are written in big endian form"
+//n.b. ASCII reading is slow - strlst.DelimitedText much slower than readln!
+label
+   666;
+const
+  kBlockSz = 4096;
+type
+  TPoint4i = packed record
+  N: longint;
+  X: longint; //ensure 32-bit for simple GIfTI writing
+  Y: longint;
+  Z: longint;
+end;
+
+var
+   f: TFByte;//TextFile;
+   strlst: TStringList;
+   str: string;
+   strips: array of int32;
+   c, i, j, k, num_v, num_f, num_f_allocated, num_strip, cnt: integer;
+   //nV: LongInt;
+   faces4: array of TPoint4i;
+   ok: boolean;
+   isBinary: boolean = true;
+begin
+  if (FSize(FileName) < 64) then exit;
+  strlst:=TStringList.Create;
+  FileMode := fmOpenRead;
+  AssignFile(f, FileName);
+  num_f := 0;
+  Reset(f,1);
+  ReadLnBinVTK(f, str); //signature: '# vtk DataFile'
+  if pos('VTK', UpperCase(str)) <> 3 then begin
+    showmessage('Not a VTK file');
+    goto 666;
+  end;
+  ReadLnBinVTK(f, str); //comment: 'Comment: created with MRIcroS'
+  ReadLnBinVTK(f, str); //kind: 'BINARY' or 'ASCII'
+  if pos('BINARY', UpperCase(str)) <> 0 then
+     isBinary := true
+  else if pos('ASCII', UpperCase(str)) <> 0 then begin
+     isBinary := false;
+     //next lines optional but faster!
+     closefile(f);
+     strlst.free;
+     LoadVtkTxt(FileName);
+     exit;
+  end else begin  // '# vtk DataFile'
+     showmessage('VTK data should be ASCII or binary, not "'+str+'"');
+     goto 666;
+  end;
+  ok := ReadLnBinVTK(f, str); // kind, e.g. "DATASET POLYDATA" or "DATASET STRUCTURED_ POINTS"
+  if not ok then goto 666;
+  while (str='') and (not eof(f)) do ReadLnBinVTK(f, str);
+  if pos('POLYDATA', UpperCase(str)) = 0 then begin
+    showmessage('Only able to read VTK images saved as POLYDATA, not '+ str);
+    goto 666;
+  end;
+  ReadLnBin(f, str); // number of vertices, e.g. "POINTS 685462 float"
+  if pos('POINTS', UpperCase(str)) <> 1 then begin
+    showmessage('Expected header to report "POINTS" not '+ str);
+    goto 666;
+  end;
+  num_v := 0;
+  strlst.DelimitedText := str;
+  num_v := StrToIntDef(strlst[1],0);
+  if (num_v < 1) or (pos('FLOAT', UpperCase(strlst[2])) <> 1) then begin
+    showmessage('Expected at least 1 point of type FLOAT, not '+ str);
+    goto 666;
+  end;
+  setlength(vertices, num_v); //vertices = zeros(num_f, 9);
+  if isBinary then begin
+     blockread(f, vertices[0], 3 * 4 * num_v);
+     {$IFDEF ENDIAN_LITTLE} // VTK is ALWAYS big endian!
+     for i := 0 to (num_v -1) do begin
+            SwapSingle(vertices[i].X);
+            SwapSingle(vertices[i].Y);
+            SwapSingle(vertices[i].Z);
+     end;
+     {$ENDIF}
+  end else begin //if binary else ASCII
+       for i := 0 to (num_v-1) do begin
+         //n.b. ParaView and Mango pack multiple vertices per line, so we can not use ReadLnBin(f, str);
+           vertices[i].X := StrToFloatDef(ReadNumBin(f),0);
+           vertices[i].Y := StrToFloatDef(ReadNumBin(f),0);
+           vertices[i].Z := StrToFloatDef(ReadNumBin(f),0);
+       end;
+  end;
+  ReadLnBin(f, str); // number of vertices, e.g. "POLYGONS 1380 5520"
+  while (str = '') and (not EOF(f)) do ReadLnBin(f, str);
+  if pos('LINES', UpperCase(str)) > 0 then begin
+    showmessage('This is a fiber file: rename with a ".fib" extension and use Tracks/Open to view: '+ str);
+    goto 666;
+  end;
+  if pos('METADATA', UpperCase(str)) = 1 then begin //ParaView inserts a metadata block
+    //http://www.vtk.org/doc/nightly/html/IOLegacyInformationFormat.html
+    while (str <> '') and (not EOF(f)) do ReadLnBin(f, str); // The metadata block is terminated by an empty line
+    ReadLnBin(f, str);
+  end;
+  if pos('TRIANGLE_STRIPS', UpperCase(str)) = 1 then begin
+     strlst.DelimitedText := str;
+     num_strip := StrToIntDef(strlst[1],0);
+     cnt := StrToIntDef(strlst[2],0);
+     num_f_allocated := cnt;
+     (*if isBinary then begin
+        showmessage(format('Unable to read VTK binary "TRIANGLE_STRIPS" %d %d', [num_strip, cnt]));
+        goto 666;
+     end;*)
+     setlength(faces, num_f_allocated); //not sure how many triangles, lets guess
+     num_f := 0;
+     if isBinary then begin
+       //Harvard Surgical Planning Laboratory MRB files are zip files with binary VTK Triangle_Strips
+       c := cnt;
+       setlength(strips, cnt); //vertices = zeros(num_f, 9);
+       blockread(f, strips[0], 4 * cnt);
+       {$IFDEF ENDIAN_LITTLE} // VTK is ALWAYS big endian!
+       for i := 0 to (cnt -1) do
+           SwapLongInt(strips[i]);
+       {$ENDIF}
+       k := 0;
+       for i := 0 to (num_strip -1) do begin
+           cnt := strips[k];
+           k := k + 1;
+           if ((cnt < 3) or (k > c)) then begin
+              setlength(faces,0);
+              num_f := 0;
+              goto 666;
+           end;
+           if ((num_f+cnt) > num_f_allocated) then begin //need to allocate more faces
+              num_f_allocated := num_f_allocated + cnt + kBlockSz;
+              setlength(faces, num_f_allocated);
+           end;
+            faces[num_f].X := strips[k];
+            faces[num_f].Y := strips[k+1];
+            faces[num_f].Z := strips[k+2];
+            k := k + 3;
+            num_f := num_f + 1;
+            if (cnt > 3) then begin
+               for j := 4 to cnt do begin
+                   //http://ogldev.atspace.co.uk/www/tutorial27/tutorial27.html
+                   //  winding order is reversed on the odd triangles
+                   if odd(j) then begin //ITK snap triangle winding reverses with each new point
+                      faces[num_f].X := strips[k-2];
+                      faces[num_f].Y := strips[k-1];
+                   end else begin
+                     faces[num_f].X := strips[k-1];
+                     faces[num_f].Y := strips[k-2];
+                   end;
+                 faces[num_f].Z := strips[k];
+                 k := k + 1;
+                 num_f := num_f + 1;
+              end; //for j: each additional strip point
+           end; //cnt > 3
+       end; //for i: each strip
+     end else begin
+       for i := 0 to (num_strip -1) do begin
+           ReadLnBinVTK(f, str);
+           strlst.DelimitedText := str;
+           cnt := StrToIntDef(strlst[0],0);
+           if (cnt < 3) then begin
+              setlength(faces,0);
+              num_f := 0;
+              goto 666;
+           end;
+           if ((num_f+cnt) > num_f_allocated) then begin //need to allocate more faces
+              num_f_allocated := num_f_allocated + cnt + kBlockSz;
+              setlength(faces, num_f_allocated);
+           end;
+           faces[num_f].Y := StrToIntDef(strlst[1],0);
+           faces[num_f].X := StrToIntDef(strlst[2],0);
+           faces[num_f].Z := StrToIntDef(strlst[3],0);
+           num_f := num_f + 1;
+           if (cnt > 3) then begin
+              for j := 4 to cnt do begin
+                  //http://ogldev.atspace.co.uk/www/tutorial27/tutorial27.html
+                  //  winding order is reversed on the odd triangles
+                  if odd(j) then begin //ITK snap triangle winding reverses with each new point
+                     faces[num_f].X := StrToIntDef(strlst[j-1],0);
+                     faces[num_f].Y := StrToIntDef(strlst[j-2],0);
+                  end else begin
+                    faces[num_f].X := StrToIntDef(strlst[j-2],0);
+                    faces[num_f].Y := StrToIntDef(strlst[j-1],0);
+                  end;
+                faces[num_f].Z := StrToIntDef(strlst[j],0);
+                  num_f := num_f + 1;
+              end; //for j: each additional strip point
+           end; //cnt > 3
+       end; //for i: each strip
+     end; //if binary else ASCII
+     setlength(faces, num_f);
+     goto 666;
+
+  end;
+  if pos('POLYGONS', UpperCase(str)) <> 1 then begin
+    showmessage('Expected header to report "TRIANGLE_STRIPS" or "POLYGONS" not '+ str);
+    goto 666;
+  end;
+  strlst.DelimitedText := str;
+  num_f := StrToIntDef(strlst[1],0);
+  cnt := StrToIntDef(strlst[2],0);
+  if cnt <> (num_f * 4) then begin
+     showmessage('Only able to read triangular meshes, not '+ str);
+     goto 666;
+  end;
+  setlength(faces, num_f);
+  if isBinary then begin
+    {$DEFINE FASTVTK}
+    {$IFDEF FASTVTK}
+    setlength(faces4, num_f);
+    blockread(f, faces4[0], num_f*sizeof(TPoint4i));
+    for i := 0 to (num_f -1) do begin
+        faces[i].X := faces4[i].X;
+        faces[i].Y := faces4[i].Y;
+        faces[i].Z := faces4[i].Z;
+    end;
+    faces4 := nil;
+    {$ELSE}
+    for i := 0 to (num_f -1) do begin
+        blockread(f, nV, sizeof(LongInt));
+        {$IFDEF ENDIAN_LITTLE}
+        SwapLongInt(nV);
+        {$ENDIF}
+        if (nV <> 3) then begin
+           showmessage('VTK file is borked');
+           goto 666;
+        end;
+        blockread(f, faces[i],  3 * 4);
+    end;
+    {$ENDIF}
+    {$IFDEF ENDIAN_LITTLE} // VTK is ALWAYS big endian!
+    for i := 0 to (num_f -1) do begin
+           SwapLongInt(faces[i].X);
+           SwapLongInt(faces[i].Y);
+           SwapLongInt(faces[i].Z);
+    end;
+    (*for i := 0 to (num_v -1) do begin
+           SwapSingle(vertices[i].X);
+           SwapSingle(vertices[i].Y);
+           SwapSingle(vertices[i].Z);
+    end;*)
+    {$ENDIF}
+  end else begin //if binary else ASCII - indexed from 0
+      for i := 0 to (num_f -1) do begin
+          ReadLnBinVTK(f, str);
+           strlst.DelimitedText := str;
+           faces[i].X := StrToIntDef(strlst[1],0);
+           faces[i].Y := StrToIntDef(strlst[2],0);
+           faces[i].Z := StrToIntDef(strlst[3],0);
+      end;
+  end; //if binary else ASCII
+666:
+  {$DEFINE FSLvtk} //FSL first - triangle winding reversed?
+  {$IFDEF FSLvtk}  //Slicer appears to use conventional triangle winding, while FSL is reversed
+  (*if num_f > 0 then begin
+    for i := 0 to (num_f -1) do begin
+      j := faces[i].Y;
+      faces[i].Y := faces[i].X;
+      faces[i].X := j;
+    end;
+  end;*)
+  {$ENDIF}
+  closefile(f);
+  strlst.free;
+end; // LoadVtk()
+{$ELSE}
 procedure TMesh.LoadVtk(const FileName: string);
 //Read VTK mesh
 // https://github.com/bonilhamusclab/MRIcroS/blob/master/%2BfileUtils/%2Bvtk/readVtk.m
@@ -6551,6 +6877,7 @@ procedure TMesh.LoadVtk(const FileName: string);
   end;
   setlength(vertices, num_v); //vertices = zeros(num_f, 9);
   if isBinary then begin
+    showmessage(inttostr(filepos(f)));
      blockread(f, vertices[0], 3 * 4 * num_v);
      {$IFDEF ENDIAN_LITTLE} // VTK is ALWAYS big endian!
      for i := 0 to (num_v -1) do begin
@@ -6745,6 +7072,9 @@ procedure TMesh.LoadVtk(const FileName: string);
   strlst.free;
 end; // LoadVtk()
 
+
+{$ENDIF}
+
 function TMesh.CheckMesh: boolean;
 //faces should be indexed for range 0..[number of triangles -1]
 var
diff --git a/nifti_foreign.pas b/nifti_foreign.pas
index 818f456..da08eaa 100755
--- a/nifti_foreign.pas
+++ b/nifti_foreign.pas
@@ -750,20 +750,138 @@ function cleanStr (S:string): string; // "(12.31)" ->"12.31"
 end;*)
 
 type TFByte =  File of Byte;
-procedure ReadLnBin(var f: TFByte; var s: string);
-const
-  kEOLN = $0A;
+  function ReadLnBin(var f: TFByte; var s: string; skipEmptyLines: boolean = false): boolean;
+  const
+    kEOLN = $0A;
+    kCR = $0D;
+  var
+     bt : Byte;
+  begin
+       s := '';
+       if EOF(f) then exit(false);
+       while (not  EOF(f)) do begin
+             Read(f,bt);
+             if (bt = kCR) then continue;
+             if (bt = kEOLN) and ((not skipEmptyLines) or (s <> '' )) then exit(true);
+             if (bt = kEOLN) then continue;
+             s := s + Chr(bt);
+       end;
+       exit(true);
+  end;
+
+(*function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int64; var swapEndian: boolean; var xDim64: int64): boolean;
+//VTK Simple Legacy Formats : STRUCTURED_POINTS : BINARY
+// http://daac.hpc.mil/gettingStarted/VTK_DataFormats.html
+// https://github.com/bonilhamusclab/MRIcroS/blob/master/%2BfileUtils/%2Bvtk/readVtk.m
+// http://www.ifb.ethz.ch/education/statisticalphysics/file-formats.pdf
+// ftp://ftp.tuwien.ac.at/visual/vtk/www/FileFormats.pdf
+//  "The VTK data files described here are written in big endian form"
+label
+   666;
 var
-   bt : Byte;
+   f: TFByte;//TextFile;
+   strlst: TStringList;
+   str: string;
+   i, num_vox: integer;
+   ok: boolean;
 begin
-     s := '';
-     while (not  EOF(f)) do begin
-           Read(f,bt);
-           if bt = kEOLN then exit;
-           s := s + Chr(bt);
-     end;
-end;
-
+  gzBytes := 0;
+  {$IFDEF ENDIAN_BIG}
+  swapEndian := false;
+  {$ELSE}
+  swapEndian := true;
+  {$ENDIF}
+  result := false;
+  strlst:=TStringList.Create;
+  FileMode := fmOpenRead;
+  AssignFile(f, fname);
+  {$IFDEF FPC} Reset(f,1); {$ELSE} Reset(f); {$ENDIF}
+  ReadLnBin(f, str); //signature: '# vtk DataFile'
+  if pos('VTK', UpperCase(str)) <> 3 then begin
+    showmessage('Not a VTK file');
+    goto 666;
+  end;
+  ReadLnBin(f, str); //comment: 'Comment: created with MRIcroS'
+  ReadLnBin(f, str, true); //kind: 'BINARY' or 'ASCII'
+  if pos('BINARY', UpperCase(str)) < 1 then begin  // '# vtk DataFile'
+     showmessage('Only able to read binary VTK file: "'+str+'"');
+     goto 666;
+  end;
+  ReadLnBin(f, str, true); // kind, e.g. "DATASET POLYDATA" or "DATASET STRUCTURED_ POINTS"
+  if pos('STRUCTURED_POINTS', UpperCase(str)) = 0 then begin
+    showmessage('Only able to read VTK images saved as STRUCTURED_POINTS, not '+ str);
+    goto 666;
+  end;
+  ok := true;
+  while (ok) and (pos('POINT_DATA', UpperCase(str)) = 0) do begin
+    ok := ReadLnBin(f, str, true);
+    strlst.DelimitedText := str;
+    if pos('DIMENSIONS', UpperCase(str)) <> 0 then begin //e.g. "DIMENSIONS 128 128 128"
+       nhdr.dim[1] := StrToIntDef(strlst[1],1);
+       xDim64 := StrToIntDef(strlst[1],1);
+       nhdr.dim[2] := StrToIntDef(strlst[2],1);
+       nhdr.dim[3] := StrToIntDef(strlst[3],1);
+    end; //dimensions
+    if (pos('ASPECT_RATIO', UpperCase(str)) <> 0) or (pos('SPACING', UpperCase(str)) <> 0) then begin //e.g. "ASPECT_RATIO 1.886 1.886 1.913"
+      nhdr.pixdim[1] := StrToFloatDef(strlst[1],1);
+      nhdr.pixdim[2] := StrToFloatDef(strlst[2],1);
+      nhdr.pixdim[3] := StrToFloatDef(strlst[3],1);
+      //showmessage(format('%g %g %g',[nhdr.pixdim[1], nhdr.pixdim[2], nhdr.pixdim[3] ]));
+    end; //aspect ratio
+    if (pos('ORIGIN', UpperCase(str)) <> 0) then begin //e.g. "ASPECT_RATIO 1.886 1.886 1.913"
+      nhdr.srow_x[3] := -StrToFloatDef(strlst[1],1);
+      nhdr.srow_y[3] := -StrToFloatDef(strlst[2],1);
+      nhdr.srow_z[3] := -StrToFloatDef(strlst[3],1);
+      //showmessage(format('%g %g %g',[nhdr.pixdim[1], nhdr.pixdim[2], nhdr.pixdim[3] ]));
+    end; //aspect ratio
+  end; //not POINT_DATA
+  if pos('POINT_DATA', UpperCase(str)) = 0 then goto 666;
+  num_vox :=  StrToIntDef(strlst[1],0);
+  if num_vox <> (nhdr.dim[1] * nhdr.dim[2] * nhdr.dim[3]) then begin
+     showmessage(format('Expected POINT_DATA to equal %dx%dx%d',[nhdr.dim[1], nhdr.dim[2], nhdr.dim[3] ]));
+     goto 666;
+  end;
+  ReadLnBin(f, str, true);
+  if pos('SCALARS', UpperCase(str)) = 0 then goto 666; //"SCALARS scalars unsigned_char"
+  strlst.DelimitedText := str;
+  str := UpperCase(strlst[2]);
+  //dataType is one of the types bit, unsigned_char, char, unsigned_short, short, unsigned_int, int, unsigned_long, long, float, or double
+  if pos('UNSIGNED_CHAR', str) <> 0 then
+      nhdr.datatype := kDT_UINT8 //
+  else if pos('SHORT', str) <> 0 then
+       nhdr.datatype := kDT_INT16 //
+  else if pos('UNSIGNED_SHORT', str) <> 0 then
+       nhdr.datatype := kDT_UINT16 //
+  else if pos('INT', str) <> 0 then
+       nhdr.datatype := kDT_INT32 //
+  else  if pos('FLOAT', str) <> 0 then
+      nhdr.datatype := kDT_FLOAT
+  else  if pos('DOUBLE', str) <> 0 then
+      nhdr.datatype := kDT_DOUBLE
+  else begin
+        showmessage('Unknown VTK scalars type '+str);
+        goto 666;
+  end;
+  convertForeignToNifti(nhdr);
+  //showmessage(inttostr(nhdr.datatype));
+  ReadLnBin(f, str, true);
+  if pos('LOOKUP_TABLE', UpperCase(str)) = 0 then goto 666; //"LOOKUP_TABLE default"
+  nhdr.vox_offset := filepos(f);
+  //fill matrix
+  for i := 0 to 2 do begin
+    nhdr.srow_x[i] := 0;
+    nhdr.srow_y[i] := 0;
+    nhdr.srow_z[i] := 0;
+  end;
+  nhdr.srow_x[0] := nhdr.pixdim[1];
+  nhdr.srow_y[1] := nhdr.pixdim[2];
+  nhdr.srow_z[2] := nhdr.pixdim[3];
+  //showmessage('xx' +inttostr( filepos(f) ));
+  result := true;
+  666:
+  closefile(f);
+  strlst.Free;
+end;*)
 function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int64; var swapEndian: boolean; var xDim64: int64): boolean;
 //VTK Simple Legacy Formats : STRUCTURED_POINTS : BINARY
 // http://daac.hpc.mil/gettingStarted/VTK_DataFormats.html
@@ -771,6 +889,9 @@ function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int
 // http://www.ifb.ethz.ch/education/statisticalphysics/file-formats.pdf
 // ftp://ftp.tuwien.ac.at/visual/vtk/www/FileFormats.pdf
 //  "The VTK data files described here are written in big endian form"
+//Some VTK datasets seem to insert empty lines (e.g. 0x0A0A instead of 0x0A: "ironProt.vtk"
+//   https://www.aliza-dicom-viewer.com/download/datasets
+//   https://vtk.org/vtk-textbook-examples-and-data/
 label
    666;
 var
@@ -778,8 +899,10 @@ function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int
    strlst: TStringList;
    str: string;
    i, num_vox: integer;
+   ok: boolean;
 begin
   gzBytes := 0;
+  xDim64 := 0;
   {$IFDEF ENDIAN_BIG}
   swapEndian := false;
   {$ELSE}
@@ -787,8 +910,8 @@ function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int
   {$ENDIF}
   result := false;
   strlst:=TStringList.Create;
-  FileMode := fmOpenRead;
   AssignFile(f, fname);
+  FileMode := fmOpenRead;
   {$IFDEF FPC} Reset(f,1); {$ELSE} Reset(f); {$ENDIF}
   ReadLnBin(f, str); //signature: '# vtk DataFile'
   if pos('VTK', UpperCase(str)) <> 3 then begin
@@ -796,18 +919,22 @@ function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int
     goto 666;
   end;
   ReadLnBin(f, str); //comment: 'Comment: created with MRIcroS'
-  ReadLnBin(f, str); //kind: 'BINARY' or 'ASCII'
-  if pos('BINARY', UpperCase(str)) <> 1 then begin  // '# vtk DataFile'
-     showmessage('Only able to read binary VTK file:'+str);
+  showmessage(str);
+  ReadLnBin(f, str, true); //kind: 'BINARY' or 'ASCII'
+  showmessage(str);
+  if pos('BINARY', UpperCase(str)) < 1 then begin  // '# vtk DataFile'
+     showmessage('Only able to read binary VTK files, not "'+str+'"');
      goto 666;
   end;
-  ReadLnBin(f, str); // kind, e.g. "DATASET POLYDATA" or "DATASET STRUCTURED_ POINTS"
+  ReadLnBin(f, str, true); // kind, e.g. "DATASET POLYDATA" or "DATASET STRUCTURED_ POINTS"
   if pos('STRUCTURED_POINTS', UpperCase(str)) = 0 then begin
     showmessage('Only able to read VTK images saved as STRUCTURED_POINTS, not '+ str);
     goto 666;
   end;
-  while (str <> '') and (pos('POINT_DATA', UpperCase(str)) = 0) do begin
-    ReadLnBin(f, str);
+  //while (str <> '') and (pos('POINT_DATA', UpperCase(str)) = 0) do begin
+  ok := true;
+  while (ok) and (pos('POINT_DATA', UpperCase(str)) = 0) do begin
+    ok := ReadLnBin(f, str, true);
     strlst.DelimitedText := str;
     if pos('DIMENSIONS', UpperCase(str)) <> 0 then begin //e.g. "DIMENSIONS 128 128 128"
        nhdr.dim[1] := StrToIntDef(strlst[1],1);
@@ -834,7 +961,7 @@ function readVTKHeader (var fname: string; var nhdr: TNIFTIhdr; var gzBytes: int
      showmessage(format('Expected POINT_DATA to equal %dx%dx%d',[nhdr.dim[1], nhdr.dim[2], nhdr.dim[3] ]));
      goto 666;
   end;
-  ReadLnBin(f, str);
+  ReadLnBin(f, str, true);
   if pos('SCALARS', UpperCase(str)) = 0 then goto 666; //"SCALARS scalars unsigned_char"
   strlst.DelimitedText := str;
   str := UpperCase(strlst[2]);
diff --git a/surfice.lpr b/surfice.lpr
index 8d73260..06468ed 100755
--- a/surfice.lpr
+++ b/surfice.lpr
@@ -17,7 +17,7 @@
   Application.Title:='Surf Ice';
   Application.Initialize;
   Application.CreateForm(TGLForm1, GLForm1);
-  ConstrainTrackBars();
+  //ConstrainTrackBars(); //if unpatched: https://bugs.freepascal.org/view.php?id=35861
   Application.Run;
   //Windows: if you get an error "Can't find object file" you can copy the 'static' folder from
   //  https://github.com/synopse/mORMot
diff --git a/surfice.lps b/surfice.lps
index 5a93eab..b12d28d 100644
--- a/surfice.lps
+++ b/surfice.lps
@@ -3,7 +3,7 @@
   <ProjectSession>
     <Version Value="12"/>
     <BuildModes Active="Default"/>
-    <Units Count="47">
+    <Units Count="45">
       <Unit0>
         <Filename Value="surfice.lpr"/>
         <IsPartOfProject Value="True"/>
@@ -18,8 +18,8 @@
         <ComponentName Value="GLForm1"/>
         <HasResources Value="True"/>
         <ResourceBaseClass Value="Form"/>
-        <TopLine Value="843"/>
-        <CursorPos X="37" Y="862"/>
+        <TopLine Value="2545"/>
+        <CursorPos X="28" Y="2562"/>
         <UsageCount Value="200"/>
         <Loaded Value="True"/>
         <LoadedDesigner Value="True"/>
@@ -29,7 +29,7 @@
         <Filename Value="PasZip.pas"/>
         <EditorIndex Value="-1"/>
         <CursorPos X="63" Y="4655"/>
-        <UsageCount Value="147"/>
+        <UsageCount Value="143"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit2>
       <Unit3>
@@ -39,7 +39,7 @@
         <ResourceBaseClass Value="Form"/>
         <EditorIndex Value="-1"/>
         <CursorPos X="14" Y="194"/>
-        <UsageCount Value="160"/>
+        <UsageCount Value="156"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit3>
       <Unit4>
@@ -47,14 +47,14 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="294"/>
         <CursorPos X="34" Y="296"/>
-        <UsageCount Value="171"/>
+        <UsageCount Value="167"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit4>
       <Unit5>
         <Filename Value="nifti_loader.pas"/>
         <EditorIndex Value="-1"/>
         <CursorPos X="20" Y="25"/>
-        <UsageCount Value="127"/>
+        <UsageCount Value="123"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit5>
       <Unit6>
@@ -62,15 +62,16 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="72"/>
         <CursorPos X="28" Y="76"/>
-        <UsageCount Value="161"/>
+        <UsageCount Value="157"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit6>
       <Unit7>
         <Filename Value="track.pas"/>
-        <EditorIndex Value="-1"/>
-        <TopLine Value="29"/>
-        <CursorPos X="5" Y="50"/>
-        <UsageCount Value="131"/>
+        <EditorIndex Value="1"/>
+        <TopLine Value="825"/>
+        <CursorPos X="17" Y="840"/>
+        <UsageCount Value="127"/>
+        <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit7>
       <Unit8>
@@ -78,7 +79,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="325"/>
         <CursorPos Y="457"/>
-        <UsageCount Value="131"/>
+        <UsageCount Value="127"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit8>
       <Unit9>
@@ -86,7 +87,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="111"/>
         <CursorPos X="21" Y="131"/>
-        <UsageCount Value="124"/>
+        <UsageCount Value="120"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit9>
       <Unit10>
@@ -94,7 +95,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="116"/>
         <CursorPos X="17" Y="129"/>
-        <UsageCount Value="125"/>
+        <UsageCount Value="121"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit10>
       <Unit11>
@@ -102,7 +103,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="520"/>
         <CursorPos X="78" Y="550"/>
-        <UsageCount Value="114"/>
+        <UsageCount Value="110"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit11>
       <Unit12>
@@ -110,7 +111,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="116"/>
         <CursorPos X="94" Y="155"/>
-        <UsageCount Value="112"/>
+        <UsageCount Value="108"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit12>
       <Unit13>
@@ -118,13 +119,15 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="202"/>
         <CursorPos X="74" Y="224"/>
-        <UsageCount Value="130"/>
+        <UsageCount Value="126"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit13>
       <Unit14>
         <Filename Value="mesh.pas"/>
-        <EditorIndex Value="2"/>
-        <CursorPos X="3" Y="6"/>
+        <IsVisibleTab Value="True"/>
+        <EditorIndex Value="4"/>
+        <TopLine Value="8735"/>
+        <CursorPos X="20" Y="8746"/>
         <UsageCount Value="108"/>
         <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
@@ -134,7 +137,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="270"/>
         <CursorPos X="40" Y="275"/>
-        <UsageCount Value="74"/>
+        <UsageCount Value="70"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit15>
       <Unit16>
@@ -142,21 +145,21 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="1342"/>
         <CursorPos X="57" Y="1351"/>
-        <UsageCount Value="108"/>
+        <UsageCount Value="104"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit16>
       <Unit17>
         <Filename Value="matmath.pas"/>
         <EditorIndex Value="-1"/>
         <CursorPos X="11" Y="10"/>
-        <UsageCount Value="70"/>
+        <UsageCount Value="66"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit17>
       <Unit18>
         <Filename Value="define_types.pas"/>
-        <IsVisibleTab Value="True"/>
-        <EditorIndex Value="5"/>
-        <CursorPos X="25" Y="10"/>
+        <EditorIndex Value="8"/>
+        <TopLine Value="32"/>
+        <CursorPos X="28" Y="47"/>
         <UsageCount Value="110"/>
         <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
@@ -166,7 +169,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="8594"/>
         <CursorPos X="4" Y="8623"/>
-        <UsageCount Value="7"/>
+        <UsageCount Value="3"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit19>
       <Unit20>
@@ -174,7 +177,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="583"/>
         <CursorPos X="47" Y="601"/>
-        <UsageCount Value="91"/>
+        <UsageCount Value="87"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit20>
       <Unit21>
@@ -183,12 +186,12 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="4744"/>
         <CursorPos X="3" Y="4753"/>
-        <UsageCount Value="10"/>
+        <UsageCount Value="6"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit21>
       <Unit22>
         <Filename Value="opts.inc"/>
-        <EditorIndex Value="1"/>
+        <EditorIndex Value="3"/>
         <CursorPos X="28" Y="4"/>
         <UsageCount Value="120"/>
         <Loaded Value="True"/>
@@ -199,7 +202,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="79"/>
         <CursorPos X="8" Y="345"/>
-        <UsageCount Value="75"/>
+        <UsageCount Value="71"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit23>
       <Unit24>
@@ -207,7 +210,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="42"/>
         <CursorPos X="42" Y="449"/>
-        <UsageCount Value="13"/>
+        <UsageCount Value="9"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit24>
       <Unit25>
@@ -215,7 +218,7 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="27"/>
         <CursorPos X="6" Y="43"/>
-        <UsageCount Value="99"/>
+        <UsageCount Value="95"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit25>
       <Unit26>
@@ -224,14 +227,15 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="46"/>
         <CursorPos X="6" Y="50"/>
-        <UsageCount Value="62"/>
+        <UsageCount Value="58"/>
       </Unit26>
       <Unit27>
         <Filename Value="commandsu.pas"/>
-        <EditorIndex Value="-1"/>
-        <TopLine Value="850"/>
-        <CursorPos X="31" Y="861"/>
-        <UsageCount Value="99"/>
+        <EditorIndex Value="2"/>
+        <TopLine Value="842"/>
+        <CursorPos X="25" Y="868"/>
+        <UsageCount Value="116"/>
+        <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit27>
       <Unit28>
@@ -239,14 +243,14 @@
         <UnitName Value="FileUtil"/>
         <EditorIndex Value="-1"/>
         <CursorPos X="44"/>
-        <UsageCount Value="90"/>
+        <UsageCount Value="86"/>
       </Unit28>
       <Unit29>
         <Filename Value="curv.pas"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="68"/>
         <CursorPos X="26" Y="95"/>
-        <UsageCount Value="69"/>
+        <UsageCount Value="65"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
       </Unit29>
       <Unit30>
@@ -255,255 +259,237 @@
         <EditorIndex Value="-1"/>
         <TopLine Value="559"/>
         <CursorPos X="14" Y="583"/>
-        <UsageCount Value="40"/>
+        <UsageCount Value="36"/>
       </Unit30>
       <Unit31>
-        <Filename Value="/usr/local/share/fpcsrc/rtl/objpas/sysutils/filutilh.inc"/>
-        <EditorIndex Value="-1"/>
-        <TopLine Value="150"/>
-        <CursorPos X="50" Y="176"/>
-        <UsageCount Value="2"/>
-      </Unit31>
-      <Unit32>
-        <Filename Value="/usr/local/share/fpcsrc/rtl/objpas/types.pp"/>
-        <UnitName Value="Types"/>
-        <EditorIndex Value="-1"/>
-        <TopLine Value="255"/>
-        <CursorPos X="25" Y="261"/>
-        <UsageCount Value="2"/>
-      </Unit32>
-      <Unit33>
         <Filename Value="/usr/local/share/fpcsrc/rtl/inc/systemh.inc"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="765"/>
         <CursorPos X="10" Y="785"/>
-        <UsageCount Value="34"/>
-      </Unit33>
-      <Unit34>
+        <UsageCount Value="30"/>
+      </Unit31>
+      <Unit32>
         <Filename Value="SynZip.pas"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="594"/>
         <CursorPos X="7" Y="605"/>
-        <UsageCount Value="64"/>
+        <UsageCount Value="60"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit34>
-      <Unit35>
+      </Unit32>
+      <Unit33>
         <Filename Value="/usr/local/share/fpcsrc/packages/paszlib/src/zstream.pp"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="70"/>
         <CursorPos X="9" Y="84"/>
-        <UsageCount Value="21"/>
-      </Unit35>
-      <Unit36>
+        <UsageCount Value="17"/>
+      </Unit33>
+      <Unit34>
         <Filename Value="nifti_foreign.pas"/>
-        <EditorIndex Value="-1"/>
-        <TopLine Value="1531"/>
-        <CursorPos X="27" Y="1536"/>
-        <UsageCount Value="20"/>
+        <EditorIndex Value="5"/>
+        <TopLine Value="1649"/>
+        <CursorPos X="27" Y="1664"/>
+        <UsageCount Value="39"/>
+        <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit36>
-      <Unit37>
+      </Unit34>
+      <Unit35>
         <Filename Value="clustering.pas"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="164"/>
         <CursorPos X="71" Y="175"/>
-        <UsageCount Value="14"/>
+        <UsageCount Value="10"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit37>
-      <Unit38>
+      </Unit35>
+      <Unit36>
         <Filename Value="../../../lazarus/lcl/graphics.pp"/>
         <UnitName Value="Graphics"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="2377"/>
         <CursorPos X="23" Y="2396"/>
-        <UsageCount Value="34"/>
-      </Unit38>
-      <Unit39>
+        <UsageCount Value="30"/>
+      </Unit36>
+      <Unit37>
         <Filename Value="glclrbar.pas"/>
         <EditorIndex Value="-1"/>
         <CursorPos X="18" Y="5"/>
-        <UsageCount Value="34"/>
+        <UsageCount Value="30"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit39>
-      <Unit40>
+      </Unit37>
+      <Unit38>
         <Filename Value="meshify_simplify.pas"/>
-        <EditorIndex Value="4"/>
+        <EditorIndex Value="7"/>
         <TopLine Value="226"/>
         <CursorPos X="34" Y="250"/>
-        <UsageCount Value="30"/>
+        <UsageCount Value="49"/>
         <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit40>
-      <Unit41>
+      </Unit38>
+      <Unit39>
         <Filename Value="../../../lazarus/lcl/interfaces/cocoa/cocoaint.pas"/>
         <UnitName Value="CocoaInt"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="473"/>
         <CursorPos X="20" Y="475"/>
-        <UsageCount Value="7"/>
-      </Unit41>
-      <Unit42>
+        <UsageCount Value="3"/>
+      </Unit39>
+      <Unit40>
         <Filename Value="glmtext.pas"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="56"/>
         <CursorPos X="6" Y="77"/>
-        <UsageCount Value="12"/>
+        <UsageCount Value="8"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit42>
-      <Unit43>
+      </Unit40>
+      <Unit41>
         <Filename Value="glcorearb.pas"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="263"/>
         <CursorPos X="81" Y="271"/>
-        <UsageCount Value="34"/>
+        <UsageCount Value="30"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit43>
-      <Unit44>
+      </Unit41>
+      <Unit42>
         <Filename Value="../../../lazarus/components/lazutils/graphtype.pp"/>
         <UnitName Value="GraphType"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="178"/>
         <CursorPos X="3" Y="197"/>
-        <UsageCount Value="6"/>
-      </Unit44>
-      <Unit45>
+        <UsageCount Value="2"/>
+      </Unit42>
+      <Unit43>
         <Filename Value="../../../lazarus/lcl/intfgraphics.pas"/>
         <UnitName Value="IntfGraphics"/>
         <EditorIndex Value="-1"/>
         <TopLine Value="96"/>
         <CursorPos X="3" Y="115"/>
-        <UsageCount Value="6"/>
-      </Unit45>
-      <Unit46>
+        <UsageCount Value="2"/>
+      </Unit43>
+      <Unit44>
         <Filename Value="uscale.pas"/>
-        <EditorIndex Value="3"/>
+        <EditorIndex Value="6"/>
         <TopLine Value="10"/>
-        <UsageCount Value="10"/>
+        <UsageCount Value="29"/>
         <Loaded Value="True"/>
         <DefaultSyntaxHighlighter Value="Delphi"/>
-      </Unit46>
+      </Unit44>
     </Units>
-    <JumpHistory Count="30" HistoryIndex="29">
+    <JumpHistory Count="29" HistoryIndex="28">
       <Position1>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="5337" Column="19" TopLine="5306"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2774" Column="88" TopLine="2766"/>
       </Position1>
       <Position2>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="5949" Column="16" TopLine="5918"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2668" Column="21" TopLine="2659"/>
       </Position2>
       <Position3>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6006" Column="16" TopLine="5990"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2774" Column="76" TopLine="2750"/>
       </Position3>
       <Position4>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6092" Column="16" TopLine="5997"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2668" Column="21" TopLine="2656"/>
       </Position4>
       <Position5>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6240" Column="17" TopLine="6209"/>
+        <Filename Value="nifti_foreign.pas"/>
+        <Caret Line="885" Column="23" TopLine="875"/>
       </Position5>
       <Position6>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6326" Column="7" TopLine="6295"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2776" Column="5" TopLine="2756"/>
       </Position6>
       <Position7>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6812" Column="9" TopLine="6788"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2769" Column="9" TopLine="2756"/>
       </Position7>
       <Position8>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6908" Column="9" TopLine="6876"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2807" Column="23" TopLine="2783"/>
       </Position8>
       <Position9>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6326" Column="45" TopLine="6308"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2943" Column="27" TopLine="2918"/>
       </Position9>
       <Position10>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="3020" Column="39" TopLine="2995"/>
       </Position10>
       <Position11>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="233" Column="4" TopLine="216"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="3153" Column="46" TopLine="3128"/>
       </Position11>
       <Position12>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="234" Column="8" TopLine="216"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="3685" Column="35" TopLine="3660"/>
       </Position12>
       <Position13>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="304" Column="29" TopLine="277"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="3697" Column="35" TopLine="3672"/>
       </Position13>
       <Position14>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="187" Column="35" TopLine="168"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4456" Column="26" TopLine="4431"/>
       </Position14>
       <Position15>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="212" Column="37" TopLine="180"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4458" Column="40" TopLine="4433"/>
       </Position15>
       <Position16>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="290" Column="7" TopLine="277"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4495" Column="63" TopLine="4470"/>
       </Position16>
       <Position17>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="230" Column="12" TopLine="220"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4515" Column="24" TopLine="4490"/>
       </Position17>
       <Position18>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="235" Column="19" TopLine="219"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4517" Column="23" TopLine="4492"/>
       </Position18>
       <Position19>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="233" Column="52" TopLine="224"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4518" Column="37" TopLine="4493"/>
       </Position19>
       <Position20>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="253" Column="18" TopLine="224"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4618" Column="23" TopLine="4594"/>
       </Position20>
       <Position21>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="281" Column="17" TopLine="271"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4735" Column="32" TopLine="4711"/>
       </Position21>
       <Position22>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="289" Column="38" TopLine="271"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="5547" Column="62" TopLine="5522"/>
       </Position22>
       <Position23>
-        <Filename Value="meshify_simplify.pas"/>
-        <Caret Line="290" Column="8" TopLine="271"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="4" Column="113"/>
       </Position23>
       <Position24>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="6" Column="3"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="3" Column="119"/>
       </Position24>
       <Position25>
-        <Filename Value="mesh.pas"/>
-        <Caret Line="118" Column="21" TopLine="88"/>
+        <Filename Value="mainunit.pas"/>
+        <Caret Line="2562" Column="28" TopLine="2545"/>
       </Position25>
       <Position26>
         <Filename Value="mesh.pas"/>
-        <Caret Line="140" Column="22" TopLine="110"/>
+        <Caret Line="161" Column="25" TopLine="146"/>
       </Position26>
       <Position27>
         <Filename Value="mesh.pas"/>
-        <Caret Line="2492" Column="23" TopLine="2460"/>
+        <Caret Line="7252" Column="23" TopLine="7234"/>
       </Position27>
       <Position28>
         <Filename Value="mesh.pas"/>
-        <Caret Line="2559" Column="16" TopLine="2528"/>
+        <Caret Line="7257" Column="26" TopLine="7234"/>
       </Position28>
       <Position29>
-        <Filename Value="mainunit.pas"/>
-        <Caret Line="6132" Column="27" TopLine="6130"/>
+        <Filename Value="mesh.pas"/>
+        <Caret Line="7262" Column="26" TopLine="7238"/>
       </Position29>
-      <Position30>
-        <Filename Value="mainunit.pas"/>
-        <Caret Line="862" Column="37" TopLine="843"/>
-      </Position30>
     </JumpHistory>
     <RunParams>
       <FormatVersion Value="2"/>
diff --git a/track.pas b/track.pas
index 3485574..e8ad7cc 100644
--- a/track.pas
+++ b/track.pas
@@ -828,7 +828,7 @@ function readInt: integer; //'1 348 347\n2' will return successively'1','348','3
   ReadLn(f, str); //comment: 'Comment: created with MRIcroS'
   if not ReadLnSkipBlank(str) then goto 666; //kind: 'BINARY' or 'ASCII'
   if (pos('ASCII', UpperCase(str)) <> 1) then begin  // '# vtk DataFile'
-     showmessage('Only able to read ASCII or binary VTK files: '+str);
+     showmessage('Only able to read ASCII or binary VTK tracks: '+str);
      goto 666;
   end;
   if not ReadLnSkipBlank(str) then goto 666;// kind, e.g. "DATASET POLYDATA" or "DATASET STRUCTURED_ POINTS"