[cgma-dev] Facet/Cholla engine

[David Thompson]

Hi Jane,

I've found a combination of things that allow me to build models with multiple faceted surfaces per shell. It boils down to creating disjoint sets of CubitPointData instances for each FacetSurface, but which re-use a given CubitPoint shared among facets on the same FacetSurface. When multiple FacetSurfaces are combined into a shell, the facet engine merges the duplicate vertices on their common boundaries. I tried passing an empty point_list, but that failed. Passing CubitFacetData instances to the same build_facet_surface() call that have coincident points encoded in multiple CubitPointData instances (instead of a shared instance) also fails. Attached are working examples (one build 4 FacetSurfaces from 4 triangles, the other 2 FacetSurfaces from 4 triangles).

It would be nice if the documentation for build_facet_surface() was updated to include some mention of this:

    //- Create one or more new FacetSurfaces with all of its lower
    //- order entities.  Use an optional feature_angle to break
    //- surface.
    //-
    //- Where the input CubitFacet and/or CubitQuadFacet instances
    //- share a vertex, they should reference the same CubitPoint
    //- pointer. However, no CubitPoint instance shared with a
    //- surface created by a separate call to build_facet_surface()
    //- should be referenced; if multiple build_facet_surface() calls
    //- are made, points on shared boundaries between will be merged
    //- when the a shell containing the surfaces is created.
    //-
    //- The point_list should contain exactly the points in
    //- the input facets and no others.

I still have not been able to get surface-splitting by feature_angle working, so that is probably still worth a bug report.

	David

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