Smoothing groups and tangent space normal map

[eduardo_naranjo]

Hello, first of all, I want to say that this is my first post on the forum, and if I have violated any rules, I apologize in advance.

The thing is, I was trying to emulate the workflow used in video games to optimize assets in order to understand some concepts of normal maps.

The example in question, and to simplify things, is a cube with the same smoothing group. The idea is that by baking a normal map with strong gradients, you can compensate the smoothing group errors. Therefore, we have two geometries: a low-poly cube (with the same smoothing group and UVs in a single shell) and a high-poly cube (rounded corners with a chamfer of 3). When I use the normal map generated in the bake with a standard material, you can see how the smoothing errors are corrected (second image). However, when I use a Vray Material (third image), this does not happen.

Could any of you tell me why this is happening?

Thanks in advance.
Best!

[vladimir_krastev]

Hi, thanks for posting. How do you export your gradient normal map (are you exporting it from Substance)? Do you use the MikkTSpace workflow? How does your examples look in a rendered image instead of a viewport preview?

[eduardo_naranjo]

Hi Vladimir, thanks for your quick response.

In the images above, I baked the normal map using render to texture. As far as I know, render to texture doesn't use MikkT space to calculate normals. I rendered these two images, and as you can see, there are shader errors.

I also tried baking the normal map in Substance Painter without using MikkT space. Instead, I used the tangents and binormals from 3ds Max so I don't compute them when I open a new template in Substance Painter. The real-time render looks good, with no shader issues. The problem arises when I use the normal map in V-Ray.