[Solved] Normal map and refraction performance

[Guillaume G.]

Hello,

I'm testing 3 textured glass materials for a project. I'm making 3 boxes and I'm texturing: one has lines, the second only roughness and the third a pattern of squares. I'm managing the pattern of the first and third with a normal map.

My problem is performance. My CPU (Threadripper 3970X) only runs at 60% when the windows are boxes, but returns to 100% when I replace them with simple planes. And I honestly don't understand why.

I've tried putting two planes one behind the other (one textured and the other not) > 60%.
A box with IDs where only one side is textured > 60%.
Thinshell on a box > 60%
Plane alone > 100%

In fact I have the impression that there's a problem as soon as there are two surfaces with refraction one behind the other and at least one of the two has a normal map.

Do you have the beginnings of an answer to this?

Thanks in advance.

[romullus]

You didn't mention what Corona version you are using, but my guess it's either Corona 10, or 10 HF1 If that's the case, the problem is most likely not in normal map, but in triplanar which has bug introduced in aforementioned versions. Head down to Corona download page and download latest hotfix which has that issue fixed https://corona-renderer.com/download

You can find changelog here: https://forum.corona-renderer.com/index.php?topic=41081.0

[Guillaume G.]

My bad, I usually check the latest patches but this time I completely forgot to do this obvious check. It does solve the problem.

Thanks very much for the quick reply.

[romullus]

You're welcome!