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My goal is to create an object using instances in Geometry Nodes so that I can create a lowpoly object and rip normals, etc from the GN object.

I've created a simple test setup where I'm simply distributing points on faces and then instancing on those points. I'm instancing an unwrapped mesh with a normal map. I then realize the instances because I need to do that in order to shrinkwrap to them (for lowpoly) as well as rip normals and other information. gn nodes

I've read the forums and figured out that the lost uv's can be accessed via an attribute node in the shader, so I've figured out that issue.

The latest thing is that realizing instances seems to mess with the normal information somehow. I can't tell exactly what is happening, but the normals are showing the wrong information. realize instances off realize instances on

I've tried flipping faces in GN, which doesn't solve the problem. I've tried inverting the green channel in the shader by subtracting 1, but that doesn't work either. Although my knowledge here is spotty, so I could definitely be doing something wrong.

I'm wondering two things: Why is this happening, and is there a workaround? Also, can others replicate this behavior? I wonder if I can use capture attribute or transfer attribute to take the original normals and reapply them somehow. Any ideas? Thanks so much!

dor
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  • How are you capturing your normals? – Robin Betts Feb 23 '22 at 18:00
  • Robin, thanks for your reply. I'm a little confused by the question. Do you mean in GN? I'm not doing any capturing of normals in there right now because I don't really know how to do it. BTW, I liked your answer to the question about how to create stylized leaves with GN.. – dor Feb 23 '22 at 18:10
  • I should have been clearer.. how are you 'accessing the UV's', exactly? I have some questions about that part, on my own account. – Robin Betts Feb 23 '22 at 19:29
  • @Robin Betts just by looking at the name of the uv attribute in the spreadsheet and then putting that attribute name into an attribute node in the shader editor and hooking it up the vector slot of the images that need uv's. I just saw a question on here that related to that. https://blender.stackexchange.com/questions/250690/geometry-nodes-instance-grid-with-material-parameters-for-specific-instances/250694#250694 – dor Feb 23 '22 at 20:08
  • If my problem has anything to do with yours, it's that I haven't managed to stash UV coordinates on instance Face Corners. Only on Points. So the interpolation screws everything up over UV seams. Splitting Edges cleans up the map, but, of course, would destroy your smooth normals?,.. maybe not, if you're just transferring the colors from a normal map. I may be wrong, I find it hard to reverse-engineer this stuff. Can you come up with a baby case, to share as a file with packed / associated Normal maps? – Robin Betts Feb 23 '22 at 20:19

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