Add to EXT_primitive_voxels, update figures

extensions/2.0/Vendor/EXT_implicit_cylinder_region/README.md

@@ -11,11 +11,11 @@ Draft
 
 ## Dependencies
 
-Written against the glTF 2.0 specification.
+Written against the glTF 2.0 specification. Depends on the [`KHR_implicit_shapes`](https://github.com/eoineoineoin/glTF/tree/refs/heads/collisionShapeMerge/extensions/2.0/Khronos/KHR_implicit_shapes) extension.
 
 ## Overview
 
-This extension defines a cylinder-conforming region as an additional shape type for the [`KHR_implicit_shapes`](https://github.com/eoineoineoin/glTF/tree/refs/heads/collisionShapeMerge/extensions/2.0/Khronos/KHR_implicit_shapes) extension. These regions are useful for visualizing real-world data that has been captured by cylindrical sensors.
+This extension defines a cylinder-conforming region as an additional shape type for the `KHR_implicit_shapes` extension. These regions are useful for visualizing real-world data that has been captured by cylindrical sensors.
 
 `EXT_implicit_cylinder_region` extends the `shape` object in `KHR_implicit_shapes`. The `shape.type` should be set to `"cylinder region"`. The properties define a region following the surface of a cylinder between two different radius values.
 
@@ -32,7 +32,9 @@ The cylinder is centered at the origin, where the radius is measured along the `
     </th>
   </tr>
   <tr>
-    <td><pre>
+    <td>
+
+```json
 "extensions": [
   {
     "KHR_implicit_shapes": {
@@ -51,14 +53,20 @@ The cylinder is centered at the origin, where the radius is measured along the `
     }
   }
 ]
-    </pre></td>
+```
+
+  </td>
     <td>
-    **TODO** visual example
+    <img src="figures/hollow-cylinder.png">
     </td>
   </tr>
 </table>
 
-A cylinder region may also be confined to a certain angular range. The `minAngle` and `maxAngle` properties define the angles at which the region starts and stops on the cylinder. These angular bounds are given in radians within the range `[-pi, pi]`.
+A cylinder region may also be confined to a certain angular range. The `minAngle` and `maxAngle` properties define the angles at which the region starts and stops on the cylinder.
+
+Angles are given in radians within the range `[-pi, pi]` and open clockwise around the cylinder (see figure below).
+
+![](figures/cylinder-angle.png)
 
 <table>
   <tr>
@@ -67,7 +75,9 @@ A cylinder region may also be confined to a certain angular range. The `minAngle
     </th>
   </tr>
   <tr>
-    <td><pre>
+    <td>
+
+```json
 "extensions": [
   {
     "KHR_implicit_shapes": {
@@ -80,17 +90,18 @@ A cylinder region may also be confined to a certain angular range. The `minAngle
               "maxRadius": 1,
               "height": 2,
               "minAngle": 0
-              "maxAngle": 1.57079632679
+              "maxAngle": 3.1415
             }
           }
         }
       ]
     }
   }
 ]
-    </pre></td>
+```
+</td>
     <td>
-    **TODO** visual example
+    <img src="figures/half-cylinder.png">
     </td>
   </tr>
 </table>

extensions/2.0/Vendor/EXT_implicit_ellipsoid_region/README.md

@@ -8,32 +8,27 @@
 Draft
 
 ## Dependencies
-Written against the glTF 2.0 specification.
+Written against the glTF 2.0 specification. Depends on the [`KHR_implicit_shapes`](https://github.com/eoineoineoin/glTF/tree/refs/heads/collisionShapeMerge/extensions/2.0/Khronos/KHR_implicit_shapes) extension.
 
 ## Overview
 
-This extension defines an ellipsoid-conforming region as an additional shape type for the [`KHR_implicit_shapes`](https://github.com/eoineoineoin/glTF/tree/refs/heads/collisionShapeMerge/extensions/2.0/Khronos/KHR_implicit_shapes) extension. These regions are commonly used in geospatial applications to describe volumes that conform to the curvature of the Earth, or other bodies.
+This extension defines an ellipsoid-conforming region as an additional shape type for the `KHR_implicit_shapes` extension. These regions are commonly used in geospatial applications to describe volumes that conform to the curvature of the Earth, or other bodies.
 
 `EXT_implicit_ellipsoid_region` extends the `shape` object in `KHR_implicit_shapes`. The `shape.type` should be set to `"ellipsoid region"`. The properties define the region following the surface of the ellipsoid between two different height values.
 
 The volume does not necessarily contain the full ellipsoid—and for many geospatial use cases, it will not. Rather, the ellipsoid is used as a reference from which the actual region is extruded. However, a region may be extend beneath the surface of the ellipsoid. Given the right height values, the region could contain the entire ellipsoid if desired.
 
 ### Details
 
-The reference ellipsoid is centered at the origin. The `semiMajorAxisRadius` indicates the radius of the ellipsoid in meters along the `x` and `z` axes. The radii for these axes are made equal in a conscious decision to simplify the math required to render implicit regions.
+The reference ellipsoid is centered at the origin. The `semiMajorAxisRadius` indicates the radius of the ellipsoid in meters along the `x` and `z` axes. The `semiMinorAxisRadius` indicates the radius of the ellipsoid in meters along the `y` axis.
 
-The `semiMinorAxisRadius` indicates the radius of the ellipsoid in meters along the `y` axis.
+> The `x` and `z` radii are made equal to simplify the math required to render implicit regions along the ellipsoid.
 
-The `minHeight` and `maxHeight` properties indicate the heights of the region from the ellipsoid's surface in meters. The `minHeight` should be a lower value, though not necessarily lower in magnitude. For example, `maxHeight` may be `10` meters while `minHeight` is `-100`.
+The `minHeight` and `maxHeight` properties indicate the heights of the region from the ellipsoid's surface in meters. A height of `0` sits right at the surface. Negative heights are also valid—they simply extend underneath the ellipsoid's surface.
 
-<table>
-  <tr>
-    <th>
-    Example
-    </th>
-  </tr>
-  <tr>
-    <td><pre>
+This example corresponds to the image below it:
+
+```json
 "extensions": [
   {
     "KHR_implicit_shapes": {
@@ -42,7 +37,7 @@ The `minHeight` and `maxHeight` properties indicate the heights of the region fr
           "type": "ellipsoid region",
           "extensions": {
             "EXT_implicit_ellipsoid_region": {
-              "semiMajorAxisRadius": 4,
+              "semiMajorAxisRadius": 3.5,
               "semiMinorAxisRadius": 2,
               "minHeight": 0,
               "maxHeight": 0.5
@@ -53,23 +48,13 @@ The `minHeight` and `maxHeight` properties indicate the heights of the region fr
     }
   }
 ]
-    </pre></td>
-    <td>
-    **TODO** visual example
-    </td>
-  </tr>
-</table>
+```
+
+![](figures/hollow-ellipsoid.png)
 
 An ellipsoid region may also be confined to a specific latitude and/or longitude range. The `minLatitude` and `maxLatitude` properties represent the latitude values at which the region starts and stops, defined in the range `[-pi/2, pi/2]`. Similarly, the `minLongitude` and `maxLongitude` properties represent the longitude bounds within the range `[-pi, pi]`.
 
-<table>
-  <tr>
-    <th>
-    Example
-    </th>
-  </tr>
-  <tr>
-    <td><pre>
+```json
 "extensions": [
   {
     "KHR_implicit_shapes": {
@@ -78,13 +63,13 @@ An ellipsoid region may also be confined to a specific latitude and/or longitude
           "type": "ellipsoid region",
           "extensions": {
             "EXT_implicit_ellipsoid_region": {
-              "semiMajorAxisRadius": 4,
+              "semiMajorAxisRadius": 3.5,
               "semiMinorAxisRadius": 2,
               "minHeight": 0,
               "maxHeight": 0.5,
-              "minLongitude": -1.57079632679,
+              "minLongitude": 0,
               "maxLongitude": 1.57079632679,
-              "minLatitude": 0,
+              "minLatitude": -0.78539816339,
               "maxLatitude": 0.78539816339,
             }
           }
@@ -93,12 +78,9 @@ An ellipsoid region may also be confined to a specific latitude and/or longitude
     }
   }
 ]
-    </pre></td>
-    <td>
-    **TODO** visual example
-    </td>
-  </tr>
-</table>
+```
+
+![](figures/half-ellipsoid.png)
 
 It is valid for the `maxLongitude` property to be less than `minLongitude`. This would define a region that crosses over the line at `-pi` or `pi`, equivalent to the International Date Line on Earth.