Missing textures in large meshes

Hello all,

I am not sure if this topic already exists.

Whenever I work with a large mesh (typically generated by aerial photogrammetry), any boolean operation causes the texture of the model to disappear (picture A turns into picture B). I’ve noticed that Blender can handle such meshes with less problems.

Is there any workaround this in Rhino?


Have you tried to _computevertexcolors?

I tried now. Got success only for small cuts of the model (near the edges).
However if I try to remove the closed area where I plan to implement the design the texture is lost.
Even when splitting the model in several parts the same happens.

Typically it is not possible to retain the UVs when the mesh geometry is modified, because the UV coordinates no longer match the mesh. Even though you may have modified only a small area of the mesh, the modification destroys the correspondence for all the UVs.

By modify, I mean deletion or addition of faces. Moving the faces usually does not break UVs

Some apps allow reprojecting the texture back into the modified mesh to create new UVs.

I though there was a way to do this in Rhino, but I searched for “reproject” on the forum and in the Help but I did not find anything.

Just to give you some insight Marco, this is not an accurate statement because what you see on Picture A is not a “texture” but a vertex coloring. Most photogrammetry software calculate both and Rhino has the ability to show both.

IF you have the texture for the file then you can cut and trim and delete vertices as much as you like with out having to worry about the texture getting lost, but vertex coloring is a different story.

It is actually very easy to keep the vertex coloring, but if you trim a mesh then what color should the new vertices have? Should they get closest color? Should the be an average of the connected vertices? Should they be driven by % based on distance to connected vertices?
If I remember correctly this is something McNeel never landed and thus chose to go for the “discard vertex colors if mesh is split” sollution.

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I assumed there was a texture map. But as you indicate, it could be vertex color

Trust me, it is.
If you have the texture map then just drag it from file explorer onto the object in Rhino.

Solved the issue for me.
Exported the model again using obj plus texture. Used the computevertexcolors to assign the textures to the faces. Exploded the model and then deleted the individual unwanted faces of the smaller remaining meshes.
Cannot use MeshBooleanSplit (as I was trying) since it breaks the faces and gives the either no texture or strange color to the resulting mesh.
Thank you all for the help.

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Hi @Marco28 ,

If you can upload a small obj with a texture map, I have an idea that may work for maintaining the texture after a mesh split or Boolean.