Whe offset (Entire model) value is negative then mesh is removed

[JihoKang24]

hello devs

I used offset (EntireModel) with ProjectionNormal (SignDetection) then mesh is removed. this work is correct?

result mesh don't have vertices

thank you for your helps

[Grantim]

Hello!
Could you please attach the input mesh, so we could reproduce the issue?

[JihoKang24]

hello grantim
I’ve sent the input mesh file via email and also attached an image to illustrate the issue, so you can reproduce it more easily.

I appreciate your help—thank you in advance.
Best regards,

[JihoKang24]

hello grantim
I found this error when I use entrie mode::smooth and offset is negative, projectionNormal TYPE
If when mode::standard then mesh isn't disappeared
what is difference smooth and standard?
I appreciate your help—thank you in advance.
Best regards,

[Grantim]

Hello!
Thanks for digging into it: actually mode::smooth and projectionNormal are incompatible, in Debug we fire assert at this point, but in release it is not visible. Also it is a bug that this configuration is available in MeshInspector, we will fix it!

Here are some explanations:

• Our offset functions are all voxel based, meaning that we first create distance field from mesh and then triangulate iso-surface of this field
• Smooth mode indicates using gridToMesh (that uses openvdb grid input) inside. It builds distance field with openvdb methods that can only be signed if the mesh is closed (actually using SignDetectionMode::OpenVDB in any case). If mesh is not closed, but signed distance field is required one should use SignDetectionMode::HoleWindingRule: it will post process unsinged distance field to mark "inside"/"outside"
• Standard mode indicates using marchingCubes algorithm that can process any kind of volume, so in case of SignDetectionMode::ProjectionNormal and SignDetectionMode::WindingRule it builds distance field with our algorithm.

What happened in your case:

1. Assert strike (but missed in Release configuration)
2. OpenVDB based signed distance field construction did not work because it does not support open meshes
3. Meshing output empty mesh

---

Please note that offsetOneDirection works a bit differently:

/// if your input mesh is open then please specify params.signDetectionMode = SignDetectionMode::Unsigned
/// if your input mesh is closed this function is equivalent to `generalOffsetMesh`, but in SignDetectionMode::Unsigned mode it will only keep one side (just like for open mesh)

as far as your mesh is open you should only use SignDetectionMode::Unsigned for this function