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Shadow Terminator. Iray

JovanniJovanni Posts: 87
edited August 2022 in The Commons

Hi all. I'm talking about an old problem. Nvidia talked about it 10 years ago, but we are still here. 

Let me briefly describe the problem. If the mesh resolution is low, the shadow boundary will be blocky. Okay, we have a workaround. We need to increase the number of mesh subdivisions. BUT! If you are using a bump map with a high number, the blocky shadows are bound to make themselves felt. 

We can increase the number of subdivisions again, but that's not the solution to the problem. The point is that increasing the bump makes the shadow boundary harsh. It's as if the light source is shrinking. 

The guys at blender have found a solution to the problem. And it looks good in the base mesh. You know what's funny? Nvidia sponsors Blender. Blender seems to be open source. Can't nvidia peek and make some similar solution? 

Nvidia cares about keeping the render engine unbiased and photorealistic? But wait. Imagine you have 2 characters in a scene. One of them in a sweatshirt with a strong bump and the other in a low bump t-shirt. The sweatshirt and t-shirt would have different shadow sharpness, as if they were illuminated by different light sources. Would that look photorealistic to you? 

Truth be told, I don't know how the others are doing. V-ray? Arnold? Does anyone have any experience with other render engines?

 

Base Mesh.jpg
1920 x 1080 - 904K
Post edited by Jovanni on

Comments

  • Silas3DSilas3D Posts: 609

    IIRC this issue in DS is only when using a point spotlight - other types such as sphere, disc etc or different lighting altogether should be ok?

  • JovanniJovanni Posts: 87

    Silas3D said:

    IIRC this issue in DS is only when using a point spotlight - other types such as sphere, disc etc or different lighting altogether should be ok?

    No. My example uses a sphere with a diameter of 20 cm. The shadows will be smooth, as long as the bump slider has low values (0-1).

    Here is another example. Same lighting, same t-shirts, but they have different shadows. The t-shirt on the left is without the bump map. The shadows are soft and nice. On the right is a t-shirt with a bump map. The shadows get harsh.

     

    t-shirt_1.png
    2163 x 2160 - 1M
  • Matt_CastleMatt_Castle Posts: 2,646
    edited August 2022

    I had a similar problem when trying to make a custom skin shader (it created procedural bump maps to help textures look less stretched on certain morphs or poses).

    Nvidia's techs told me to experiment with the shadow terminator offset setting. Daz's techs told me they didn't make this parameter accessible in Studio.

    Fun times. frown

    Post edited by Matt_Castle on
  • richardandtracyrichardandtracy Posts: 5,870

    Had the shadow problem myself with this image: https://www.renderosity.com/gallery/items/2877548/not-a-ruin-yet. The solution was to remove the top entirely from the character, and suddenly nobody noticed any shadow blockiness.

    Regards,

    Richard

  • Leonides02Leonides02 Posts: 1,379

    Like everyone, I've had this problem myself.

    The only "solution" I've found is to remove the bump map and spot render the area.

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