Any solutions to this jagged shadows issue?

conscience73

Rendering an indoor scene with a skylight. HDRI, no other lights.

PBR skin shader. Turning off bump, gloss, detail, translucency doesn't affect the result.

Figure is Sub 2. Sub 3 makes a slight difference but the transition is the same. Sharp, with the shadow being too dark.

Tried rendering the scene in Blender. Same HDRI. Problem doesn't exist there, it seems.

Any solutions?

Richard Haseltine

This is an example, I think, of what si called the terminator effect - the transition from the side that is facing the light to the side that is away from the light. Adjusting the nagles slightly can fix it, as can higher  levels of SubD - I think there may be other options, if you search (here or in general, though the latter will probably produce a   lot of Arnie stuff) for terminator effect (try adding rendering to the search terms)

mmdestiny

conscience73 said:

Rendering an indoor scene with a skylight. HDRI, no other lights.

PBR skin shader. Turning off bump, gloss, detail, translucency doesn't affect the result.

Figure is Sub 2. Sub 3 makes a slight difference but the transition is the same. Sharp, with the shadow being too dark.

Tried rendering the scene in Blender. Same HDRI. Problem doesn't exist there, it seems.

Any solutions?

I hate necroing threads, but as this was something I just solved for myself, I figured I'd throw an answer here for others that may need it.

The problem is in the Normal map and quad triangulation, not the bump.   That's why subd improves but doesn't solve the result.

First step would be to see if you can get a higher res Normal map.  If you're not using a normal map, then rotating the quad trangulation for the affected quads should help.

jbowler

mmdestiny said:

The problem is in the Normal map and quad triangulation, not the bump.   That's why subd improves but doesn't solve the result.

I guess it depends on the SubD level that was assumed when the normal map was generated, on the basis that the normals are relative to the surface so if the surface is subdivided the normals, unless they are interpolated correctly, get thrown off.  (I'm guessing that's what you mean by "quad triangulation"; the subdivision of the surface.)

I've noticed that a lot of products include both a normal map and a bump map for some reason (some reason that I cannot think of); why not just delete the normal map so that the bump map is used?  The bump map should interpolate (aka subdivide) correctly and it is equivalent to the normal map.  I don't have an example of this problem so I can't test that hypothesis.

eric susch

You could also try searching for "Shadow Terminator Problem" which is what I think some people call it.  It may be specific to Iray, I'm not sure.  The only way I've been able to fix it is by increasing the subD.

https://blog.irayrender.com/post/29042276644/shadow-acne-and-the-shadow-terminator

 

jbowler

eric susch said:

You could also try searching for "Shadow Terminator Problem" which is what I think some people call it.  It may be specific to Iray, I'm not sure.  The only way I've been able to fix it is by increasing the subD.

https://blog.irayrender.com/post/29042276644/shadow-acne-and-the-shadow-terminato

That is a really helpful link; thank you.  It does say this:

>While the ray tracing or rasterization will work on the actual, 'physical’ triangulated mesh, most of the material calculations will be based upon the fuzzy interpolated normals.

So SubD does help, however the article adds this end-note:

>Fortunately, the workaround is pretty simple: If you experience shadow terminator artifacts on a mesh, simply increase the triangulation, or in the case of bump/normal maps: use displacement maps instead (which looks much more realistic on mesh silhouettes anyhow).

That has me weirded out; a "bump" map is, shirley, a "displacement" map.  Or not.

Richard Haseltine

jbowler said:

eric susch said:

You could also try searching for "Shadow Terminator Problem" which is what I think some people call it.  It may be specific to Iray, I'm not sure.  The only way I've been able to fix it is by increasing the subD.

https://blog.irayrender.com/post/29042276644/shadow-acne-and-the-shadow-terminato

That is a really helpful link; thank you.  It does say this:

>While the ray tracing or rasterization will work on the actual, 'physical’ triangulated mesh, most of the material calculations will be based upon the fuzzy interpolated normals.

So SubD does help, however the article adds this end-note:

>Fortunately, the workaround is pretty simple: If you experience shadow terminator artifacts on a mesh, simply increase the triangulation, or in the case of bump/normal maps: use displacement maps instead (which looks much more realistic on mesh silhouettes anyhow).

That has me weirded out; a "bump" map is, shirley, a "displacement" map.  Or not.

No, bump and normal maps don't move anything - they cause the surface to take illumination as if it was facing in the direction the new normals (set explicitly by a bump map or calculated from the height valuews given by a bump map) specify. Displacement, on the other hand, does move the mesh (vertices from the base mesh or SubD at least, in some engines such as 3Delight and the recent versions of Iray additional vertices created on the fly to give greater detail without requiring the whole emsh to be divided). As the article says, displacement changes the outline shape and also it can cast shadows.

dtrscbrutal

 Disregard see Richards post above ( I am a slow typist  )