Variable offset STL geometry

[deshikreddyp]

Hello,
I have been using this library for a while. I offset an STL file using the following script,

from meshlib import mrmeshpy

# load non-closed mesh
closedMesh = mrmeshpy.loadMesh("closed_mesh.stl")

# setup offset parameters
params = mrmeshpy.OffsetParameters()
params.voxelSize = 1
params.type = mrmeshpy.OffsetParametersType.Offset # requires closed mesh

# create positive offset mesh
posOffset = mrmeshpy.offsetMesh(closedMesh, 0.3, params)

# save results
mrmeshpy.saveMesh(posOffset, "offset_mesh.stl")

This works very nicely. But now, I want to see if I can vary the offset based on the coordinate.
For example, if I have a cylinder as mesh, I should be getting a truncated cone, i.e, as 'z' coordinate increases, the offset in 'x' and 'y' increases.

Thanks!

[Fedr]

Thanks for using MeshLib.

In general, variable offset is a more difficult thing than a constant offset. But in your case, it looks like you can

1. warp the space, shrinking it as z coordinate increases:

[x',y']=[x,y]/z
z'=z

(all mesh points must be updated by this formula)
2. Do an ordinary constant offset
3. Warp the space (and all mesh points) back:

[x,y]=[x',y']*z
z=z'

Will it work for you?

[Fedr]

Recently we have implemented variable offset in MeshLib master branch:

/// consider a mesh where each vertex has additive weight, and this weight is linearly interpolated in mesh triangles,
/// and the distance to a point is considered equal to (euclidean distance - weight),
/// constructs iso-surface of such distance field corresponding to params.offset value using marching cubes
[[nodiscard]] MRVOXELS_API Expected<Mesh> weightedMeshShell( const Mesh & mesh, const WeightedPointsShellParameters& params );

It will be included in the nearest release together with Python API. But you can give it a try right now.