Corona Bitmap Color space/RGB primaries not working properly

[v.p.vlasenko]

Or maybe I'm doing something wrong?
Screenshot is attached

Changing RGB primaries in corona bitmap has a subtle, almost unnoticeable effect. 3dsmax bitmap working as expected by selecting color space during load (those settings not affecting corona bitmap).

Latest daily build

[maru]

I can reproduce this. We will investigate and let you know what is going on...

[maru]

Looks like passing the normal map through a Corona Color Correct mode with gamma correction 2.2 fixes this, but that should not be necessary...

[v.p.vlasenko]

yeah, I tried this as a workaround, but that's an additional step, especially when there are a lot of textures.

[maru]

This is now reported to our devs (Internal ID=1301174543) .

[v.p.vlasenko]

Hi, I'm not sure but it seems like this was fixed a while ago or not? But now in 12 update 1 I have the same problem.

[maru]

Hi, I'm not sure but it seems like this was fixed a while ago or not? But now in 12 update 1 I have the same problem.

The original problem was that Max Bitmap and Corona Bitmap would produce different results with the ACES color management mode enabled. I tested this in 3ds Max 2025 with Corona 12 U1 HF1 and all is working fine. The spheres render identically (and correctly) with both Max Bitmap and Corona Bitmap.

If you are experiencing some issue, please explain what exactly is going on.

[v.p.vlasenko]

I attached screenshot

1. Big difference between 3dsmax bitmap in RGB and RAW mode, CoronaBtmap acts differently.
2. Produces correct results without adding gamma, but still showing gamma warning. CoronaBitmap produces the same result, but need to add gamma to it.

I expected that loading the normal map as a 3dsmax bitmap and corona bitmap in raw mode should give the same results without gamma warnings or adding gamma.

[maru]

1. Big difference between 3dsmax bitmap in RGB and RAW mode, CoronaBtmap acts differently.

I was able to reproduce this but only when using a JPG bitmap as the normal map. With a 32-bit TIF it works more consistently, pretty much all the Max/Corona/sRGB/RAW combinations look the same. This is probably some color management stuff related to the fact that a JPG has sRGB gamma stored in it. I will try to get some info from our developers.

2. Produces correct results without adding gamma, but still showing gamma warning. CoronaBitmap produces the same result, but need to add gamma to it.

The gamma warning is sometimes a false positive. Corona has no way of reliably telling this. Imagine saving a bitmap in linear space and in gamma 2.2 space but in a way that the resulting pixel color values are the same - Corona will show the gamma warning in case of one of them even though they will render identically.

[maru]

Update: also, it seems that we are doing it right and something is wrong with the 3ds Max bitmap.

Corona RAW vs Max RAW - https://corona-renderer.com/comparer/06k69O

Corona RAW vs no normal - https://corona-renderer.com/comparer/hGvvND

Max RAW vs no normal - https://corona-renderer.com/comparer/HnJu2r

(Report ID=CMAX-1487)