Different result with CoronaBitmap vs 3ds Max bitmap as displacement map

[Karax]

Hi!
I used the Corona Converter to convert standard 3ds Max Bitmaps to CoronaBitmaps in a CoronaPhysical material and noticed that I got a different looking result on the displacement afterwards. See the attached image. The displacement map is a 16 bit tif image, the Min level/Max level values in the material are: -3.0 cm and 3 cm and I use default settings in both the 3ds Max bitmap and CoronaBitmap.

Does anyone know what could be the reason for this difference?

[romullus]

Most likely gamma issue. Check if the gamma is different before and after conversion. It should be the same and ideally it should have value of 1.0

[Karax]

Thanks for the reply! Where do you mean I should check the gamma value? The bitmap is connected to a CoronaColorCorrect node in the material editor, where the gamma is set to 1, but I have not modified this value between the two renders. The default gamma value in Rendering/Color Management in 3ds Max is not altered between the renders either. Also, I have not touched any settings in the bitmap nodes themselves.

[Karax]

Here are the settings in the both bitmap nodes

[Aram Avetisyan]

Hi,

Honestly, the displacement (the effect, the amount of it) looks the same to me.
What you observe, I think, is the surface brightness/reflectivity change. Maybe I am wrong.

My guess is that it was CoronaLegacyMtl originally, at the converter converted it to CoronaPhysicalMtl and hence the result, be it intended or not.

The image gamma is usually set up when loading it, in the load window.

[romullus]

Thanks for the reply! Where do you mean I should check the gamma value?

As Aram already said, you check for gamma in bitmap loader window. Displacement as well as other non colour textures should be loaded with gamma 1.0

Honestly, the displacement (the effect, the amount of it) looks the same to me.

You need to look at the intersection of ground and wall meshes, the issue is clearly visible there.

[Karax]

Ah yes, this solved it! I changed to "Override: 1.0" in the CoronaBitmap and now it looks the same as the standard Bitmap.

So, when using standard 3ds Max bitmaps there seems to be no difference between choosing "Automatic" or "Override: 1.0" regarding displacement, but for CoronaBitmaps there is a difference. In the attached image the 3 bitmap nodes within the yellow line all give the same result in the rendering (no gaps between the background wall and the ground, or below the person's feet.)

I have been using standard Bitmaps until now in most of my materials. If I start using CoronaBitmaps instead, I need to always choose Override: 1.0 for displacement maps then, right?

[romullus]

Well, that's strange, because even from material editor preview it's clear that there is a difference between automatic gamma and override 1.0 in both bitmaps. Maybe that's some kind of bug - TIFF format is notorious for the problems with 16 bits, that's why i try to avoid it whenever that's possible.

I have been using standard Bitmaps until now in most of my materials. If I start using CoronaBitmaps instead, I need to always choose Override: 1.0 for displacement maps then, right?

You should always use override gamma 1.0 for displacement textures, irrespective of map type. The only exception is when displacement texture is in EXR or HDR formats, in that case it doesn't matter if you choose automatic, or override, because 3ds Max should recognize and handle it automatically.

[Karax]

Yes I noticed the material editor previewes too and agree that it is strange that only the CoronaBitmap with Automatic behaves differently. Btw, I drew the yellow line wrong in my last image - it should be like in this new image instead (even though this does not make things less strange)

Ok, so the TIF format should be avoided for displacement maps then? The material I use here is one I bought from Textures.com and in most of their materials there seems to be TIF images for all bitmaps, including the height/displacement map. Do you recommend using 16-bit images for displacement maps, but in another format, like PNG? Or does 8 bit JPG-s work equally well?

Before trying this solution with Gamma Override: 1, I got different results in the rendering when using a 16-bit TIF image for the displacement map, compared to an 8-bit JPG, but now with the Gamma override, there is no difference anymore if I use a JPG.

[Karax]

Thanks for the reply! As romullus wrote, the difference was in the gaps between the background wall and the ground and also below the person's feet.

No, I had CoronaPhysicalMtl both before and after the conversion. But things got solved now when I switched to Gamma override: 1.

Hi,

Honestly, the displacement (the effect, the amount of it) looks the same to me.
What you observe, I think, is the surface brightness/reflectivity change. Maybe I am wrong.

My guess is that it was CoronaLegacyMtl originally, at the converter converted it to CoronaPhysicalMtl and hence the result, be it intended or not.

The image gamma is usually set up when loading it, in the load window.

[romullus]

Ok, so the TIF format should be avoided for displacement maps then?

I don't say 16bit TIFFs should be avoided, but i had issues in the past in 3ds Max with this format and my personal preference is to avoid it. Maybe TIFF format itself is perfectly fine, but the issue is on Autodesk side, i don't know and frankly i don't care, there are plenty other perfectly suitable formats.

The material I use here is one I bought from Textures.com and in most of their materials there seems to be TIF images for all bitmaps, including the height/displacement map. Do you recommend using 16-bit images for displacement maps, but in another format, like PNG? Or does 8 bit JPG-s work equally well?

If you'll do conversion, then you absolutely must keep 16 bits. Converting to 8 bits will permanently ruin your texture. That is true for displacement and for some extent for normal maps, for other maps 8 bits is perfectly enough. There are some vendors that like to save all their textures to 16 bit files, personally i think it's a crime against planet and i always try to re-save them to 8 bits to save resources. But, i'll repeat it again, displacement maps should be kept in their original bit depth!

[Karax]

Ok, thanks a lot for the help! I'll keep the 16-bit bit depth for displacement maps and always use Gamma 1 for them.

[romullus]

You're welcome! Setting gamma to override 1.0 is a sure method to have your material the way it's intended to look. Also don't forget to override gamma for other so-called data maps, like roughness, opacity, anisotropy, bump, etc.

[Karax]

Oh, that is really good to know too! So is it mainly in diffuse/albedo maps that Gamma Automatic should be used?

[romullus]

That's correct, diffuse and translucency maps should be used with automatic gamma, almost everything else should be loaded with gamma 1.0