Just wanted to chime in if anyone else out there is running into baking errors with the recent SP release 2017.3.0. The bug seems to happen when baking with "cage enabled" checked. I updated SubPainter yesterday and noticed the issues with baking, I usually assume errors are something I did, not a program issue so I redid my work a number of times until it became apparent something fishy was going on with the new release. I took half a dozen assets that I know baked perfect in the SubPainter 2017.2.0 with cage enabled and ran them through 2017.3.0, they all had baking errors.
I reverted back to 2017.2.0 and all my assets bake perfect with "cage enabled" again.
It seems that the issue is almost as if the rays being cast from the cage stop when they hit the lowpoly mesh instead of stopping when the ray hits the highpoly mesh.
Anyways just wanted to post this so if theres anyone else cage baking with the new release and is pulling their hair out, revert to 2017.2.0 for the time being and you'll be fine.
Replies