Ok, I went though your check list and found I was missing the ‘Tangent Space Normal = FALSE’ for the material used during capturing. I had set it for the final material used on the imposter sprite, but not the capture material (I may be that I simply misunderstood, but from you original instructions it seemed to imply it was just the sprite material that required the flag). Anyway, with that fixed the lighting looks much better.
The remaining problems are the odd issue which you described as the sprite being “broken up into several bits”, and some discrepancy in the imposter’s orientation. It’s much improved after your vertex shader suggestions, but the artefacts are still noticeable in certain situations, particularly when the sprite pops between frames. Sometimes it looks like its using two sprite tiles at once. You’ll also notice the orientation of the imposter doesn’t quite match the real mesh in the image below.
This could be something missing with the vertex shader. I’ve used the S_1_Unit_Plane.S_1_Unit_Plane mesh, but can you what you said before “Then either scale the mesh to be small, or subtract AbsoluteWorldPosition and add ObjectPosition in the WorldPositionOffset shader”. If I’m understanding you correctly, I did this it by inserting the calculation between the WorldPositionOffset pins of the ImposterUVs function and my sprite material (see image below).
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In the material graph image you can also see some artefacts in the thumbnail images of the texture samplers. Is that also a symptom of the same problem we see on the sprite?
Finally, how to you scale and rotate the sprite in game, since only the location on the actor’s transform works when using the vertex shader changes described above. Are you limited to using the ImposterUVs function inputs to do this?
Thanks again for your help with this, I’ll get it working eventually!