I can reproduce this. We will investigate and let you know what is going on…
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…
yeah, I tried this as a workaround, but that’s an additional step, especially when there are a lot of textures.
This is now reported to our devs (Internal ID=1301174543) .
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.
I attached screenshot
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.
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.
- 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.
Update: also, it seems that we are doing it right and something is wrong with the 3ds Max bitmap.
Corona RAW vs Max RAW - corona raw vs max raw | Corona Renderer
Corona RAW vs no normal - corona raw vs no normal | Corona Renderer
Max RAW vs no normal - max raw vs no normal | Corona Renderer
(Report ID=CMAX-1487)
Is it normal what RGB primaries at creating Corona Bitmap is Custom and i have to always change to auto? corona 12.2, max25
Hi,
Yes, Corona follows the rules set in 3ds Max color management.
If Auto and the custom (whichever primaries it comes with) give different results, please show an example to understand the case better.
3ds max color management is by default(AcesCG), if i drag and drop textures (jpg etc) it’s fine with native bitmap, if i adding corona bitmap it always RGB primaries set to custom(sRGB) and have wrong colors. Auto mode telling color space is sRGB and looks fine.
If 3ds max set to gamma color management, corona bitmap loading right linear sRGB in RGB primaries.
How to set to Auto by default?
This was a bug in Corona 12 Update 1 HF1. The solution is to use Corona 12 Update 2: Download | My Chaos
Had to return to this topic again…
Maybe I got it wrong, but I thought that linear srgb in corona bitmap should produce same result as srgb in bitmap?
drag&drop image to max set corona bitmap to linear srgb, so I have to change it manually by clicking on “Load map”->“Automatic”->“Open”. Then primaries changed to custom:srgb
But I had to do it to each texture in material from external model after converting bitmap to corona bitmap. Loading forest pack models as an example.
But what even worse - inconsistent behaviour. As I remember I loaded some gravel preset from forest pack and after converting it to corona bitmap all textures became much brighter, except one. So I had to change like 9 bitmaps to custom:srgb and left one of them as linear rgb. This one texture worked correctly with linear and wrong with custom:srgb (much darker).
I’ve encountered this issue as well: once a 3ds Max bitmap is loaded, it can’t be modified—you have to save a copy of the texture under a new name and then reload it.
-- fake code like:
bmp = bitmaptexture.bitmap
bmp_copy = copy bmp
bmp_copy.filename = "test.jpg"
bmp_copy.gamma = 1.0
save bmp_copy
bitmaptexture.bitmap = openbitmap bmp_copy.filename
This is already reported as (Report ID=CMAX-1759).
Also: (Report ID=CMAX-1791)
Any update on this?
This is fixed and the fix is present in the latest Corona Daily preview build which you can find here: https://forum.corona-renderer.com/ Chaos Corona 14 for 3ds Max - Previews (Daily Builds) Changelog
Note: The daily previews are the newest, experimental versions of Chaos Corona intended mainly for testing purposes and to showcase the recently added features. They contain the latest bug fixes but are not guaranteed to be stable, and in some cases can even damage scene files.
Check this link to know more about it: https://support.chaos.com/hc/en-us/articles/4528206493329-Corona-for-3ds-Max-Previews
Yes, I saw this and checked - the conversion is fixed, thanks. Converted corona bitmap now has custom:srgb
But the question is - shouldn’t linear srgb in corona produce the same result as custom: srgb?
Right now linear srgb is much brighter than custom srgb.
Custom is more suitabe for some other colorspaces like rec, than for srgb.
