Geometry Nodes: use smooth normals in Distribute Points on Faces node #104414

Previously, the node used the "true" normal of every looptri. Now it uses the "loop normals" which includes e.g. smooth faces and custom normals. The true normal can still be used on the points by capturing it before the Distribute node.

We do intend to expose the smooth normals separately in geometry nodes as well, but this is an important first step.

It's also necessary to generate child hair between guide hair strands that don't have visible artifacts at face boundaries.

For perfect backward compatibility, the node still has a "Legacy Normal" option in the side bar. Creating the exact same behavior with existing nodes isn't really possible unfortunately because of the specifics of how the Distribute node used to compute the normals using looptris.

Previously, the node used the "true" normal of every looptri. Now it uses the "loop normals" which includes e.g. smooth faces and custom normals. The true normal can still be used on the points by capturing it before the Distribute node. We do intend to expose the smooth normals separately in geometry nodes as well, but this is an important first step. It's also necessary to generate child hair between guide hair strands that don't have visible artifacts at face boundaries. For perfect backward compatibility, the node still has a "Legacy Normal" option in the side bar. Creating the exact same behavior with existing nodes isn't really possible unfortunately because of the specifics of how the Distribute node used to compute the normals using looptris.

distribute_points_on_torus.mp4

573 KiB

hair_artifacts_with_true_normals.mp4

398 KiB

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The code looks simple enough now. Just one suggestion inline. It might be nice to briefly describe why the corner normals are important for the hair use case in the commit message, the motivation isn't obvious without all the background right now.

Thanks, LGTM

Not gonna lie, I was confused for a second testing this on an existing file seeing it wouldn't work. Then I remembered I had to turn off the legacy toggle. Can confirm the versioning works.

I tested this a week ago already, not sure what changed in between but it looks good to me.

Not gonna lie, I was confused for a second testing this on an existing file seeing it wouldn't work. Then I remembered I had to turn off the legacy toggle. Can confirm the versioning works. I tested this a week ago already, not sure what changed in between but it looks good to me.

 @ -328,0 +347,4 @@
       const MLoopTri &looptri = looptris[looptri_index];
       const float3 &bary_coord = bary_coords[i];
       const float3 &normal0 = corner_normals[looptri.tri[0]];

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Geometry Nodes: use smooth normals in Distribute Points on Faces node #104414

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