Bump renders with inverted intensity/direction when an object has been mirrored at some point. This happens even if mesh normals face in the correct direction.
I consider it a bug since it doesn’t happen with Scanline and I can’t imagine a situation where you’d want this to happen.
Repro steps:
Create a sphere
Apply UVW modifier
Apply a Mirror or a Symmetry modifier
create a material and use a bump map
render
→ The original part of the mesh will render the bump correctly, the mirrored/symmetrical part will render the bump as inverted
See attached image for a better explanation, left - original mesh with positive bump direction, right - mesh from a symmetry modifier with negative bump direction (from the same material)
Great! I took me while to figure out why bump looked great on some parts but was totally funky on others. Ideally this should be fixed very soon, I imagine this affects a lot of projects.
Another effect of this bug is that if you flip UV coordinates it’ll also change the bump direction. That’s probably what causes it, it’s not the flipped normals but flipped UVs from the mirror/symmetry modifier.
Also this bug affects objects with shell modifier, since shell modifier flips UV coordinates. Would be great if it’d be fixed ASAP, since shell modifier and flipped UVs in general are pretty common in archviz.
Vray - keeps bump orientation correct with symmetry modifier, but when you intentionally flip faces using normal modifier, bump flips as well.
Because it happens anyway, right? If you create a plane, it will have inverted bump on one side.
OR, if it’s possible, all objects could have the same (“positive”) bump applied to both sides. I can’t imagine a situation where one would want to have a flipped bump on one side for some reason. On the other hand, transparent/refractive objects… My brain hurts.
I vote for Mental Ray’s approach. How vray can distinguish between flipped normals by various modifiers anyway? It must be something else. Fliped faces in case of symmetry modifier maybe?
Funny enough that in alpha 5 and 6 Corona didn’t have such problems with normals. Unfortunatelly A7 isn’t accesible anymore, so i can’t trace exactly when there was changes made (could be when add gamma checkbox was introduced). Anyway, Corona v1 really suffer from this in certain scenes. Take a look at the attached examples. Alpha 6.1 renders normals perfectly well despite the fact that half UVs are flipped, while V1.2 struggles much. I tried to flip all UVs back - results are much better, but still not the same as in alphas.
On a second thought, we already have a rule and that’s the bump value, positive or negative.
As long as the bump value is positive it should always render in positive way, regardless of normal, flipped UV etc. Since we don’t care about face directions in Corona bump should always render identically.
Btw, the same happens for normal maps as far as I remember, these will need a fix too.
I just followed the mantis updates and am happy to see that it’s fixed. In which version of DB/Corona exactly is this fixed? I still haven’t moved to 1.3, need to test some things, so knowing when the fix was available would be good.
We’re currently on 1.3 and it doesn’t seem like this was fixed? The brick on the right is the mirrored geometry. Oddly, that is the only geo/material that is exhibiting the problem… Any ideas, flipping normals doesnt solve it?
EDIT: Might’ve jumped the gun here sorry, looks like its directly related to mighty tiles, I’ll do some more testing and report back.
