Paint Tool on OBJ Mesh (DTM)

To start off I need to mention that I am using both LumenRT for OV and OV USD Composer to put together a scene of a project we are working on.

The original geometry is created using LRT - itwin sync, all this does is export a itwin model into the OV workspace. in this model there are buildings and a Digital Terrain Model. Once i have a saved .USD file i continue to work in USD Composer. This is where I replace the original DTM with a more detailed OBJ of the terrain.

The strange bit is that the when wanting to place trees into the scene using the paint tool, the paint tool does not recognize the OBJ as a surface to paint on to, it recognizes the buildings and nothing else.

is there any particular reason for this?

@aemvr1 i am just a fellow OV user, so take my comments with a grain of salt. can you confirm whether you see the brush radius (blue circle around where your cursor is) at all when you are attempting to paint on top of the terrain mesh? if it disappears, it’s likely that the normal of the mesh is flipped. as far as i am aware, the default behavior of the Paint Tool is meant to be painted on top of faces that have positive normal (i’ll cover how we can go around that at the end).

if you aren’t sure, you can actually visualize the normals of each polygon by going into the terrain mesh property, find the ‘Visual’ section and toggle on ‘Normals’ view


and polygons that have positive normal would be indicated with lines sticking out; otherwise, you are seeing a flipped normal that will prevent you from painting on top of the mesh.

in the above example, i have two of the exact mesh. however, the mesh on the left has normal facing upwards; the right has flipped normal. as you can imagine, i will be able to paint from the top of the mesh on the left, but in order for me to paint onto the mesh to the right, i’ll have to orbit to below the terrain in order to trigger the brush tool.

that being said, another way around it if you don’t want to jump into another DCC to address this fix, is to toggle on the ‘Double Sided’ option under ‘Visual’, which should allow you to paint no matter the normal orientations.



Could you upload the high quality Obj you are trying to paint on so I can try myself ? It should be recognized as a paintable surface.

Hey guys sorry for the delayed response was attempting to resolve this issue alone, but yes it turned out to be the normals were facing in the wrong direction from the CAD model. sneaky little issue that made me two shades greyer but that was most certainly the issue

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Great ! Good to know !

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