Bump Vs Shadows

[TBFX]

The problem with the bump mapping is the same problem as with low polygon meshes, in both cases you get what are called shadow terminator artifacts. Near the edge of the shadow there are spots where the object should be lit by the light source according to the shading normals, but where the triangle is facing away from the light source. This may occur either because of bump mapping or because of normal interpolation. The result is that the lighting on these triangles goes missing.

This is a hard problem to solve without introducing other problems such as light leaks. So for now I can't really offer any workaround. If you have a curved surface with a bump map you can try if you can increase the size of the light source, this will make the shadow edge a bit smoother.

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Roeland

Hi Roeland,

Are you seriously saying that this cannot be fixed?.... Seriously??? This is a major limiting factor at present, particularly with no displacement available. I had thought it was being addressed based on some older posts I had read on bump mapping issues but I must have been mistaken.

I've personally never used another renderer that has this issue with bump/normal mapping, including raytracers both biased and unbiased (though I have never cycles) It must be possible to fix this.

T.

[abstrax]

Yes, it's a tricky problem to solve. And C4D for example, has the same issue.

[bicket]

Abstrax, thanks for your answer
How did the tea render team to find a workaround ?
http://www.thearender.com/forum/viewtop ... =17&t=4331

[TBFX]

Thanks Abstrax,

I Understand.
Just to be clear though it is only the issue with the bump mapped terminator that is a major issue, the low poly terminator glitches are not really an issue as most production models have a poly resolution high enough, and yes these exist in most raytracing renderers but most renderers seem to get around the issue of the bump mapped terminator glitch.
Roland said they are both the same issue and I have no reason to doubt him. I'd just like to know you guys are working on a solution to this tricky problem and that one day we may have a solution. I'd like to know that it hasn't just been stuck in the too hard basket and forgotten about. It's a big issue if you are rendering anything curved and relatively smooth as the harsh terminator starts to appear with very little bump.

T.

[abstrax]

Thanks Abstrax,

I Understand.
Just to be clear though it is only the issue with the bump mapped terminator that is a major issue, the low poly terminator glitches are not really an issue as most production models have a poly resolution high enough, and yes these exist in most raytracing renderers but most renderers seem to get around the issue of the bump mapped terminator glitch.
Roland said they are both the same issue and I have no reason to doubt him. I'd just like to know you guys are working on a solution to this tricky problem and that one day we may have a solution. I'd like to know that it hasn't just been stuck in the too hard basket and forgotten about. It's a big issue if you are rendering anything curved and relatively smooth as the harsh terminator starts to appear with very little bump.

T.

I can think of at least two things we could try, but we just didn't have time to work on it yet. Too much to do, too little time...

[bicket]

The brute force solution is micro displacement ...

[TBFX]

I can think of at least two things we could try, but we just didn't have time to work on it yet. Too much to do, too little time...

Thanks Abstrax, good to know.

T.

[Karba]

Are you seriously saying that this cannot be fixed?.... Seriously???
I've personally never used another renderer that has this issue with bump/normal mapping, including raytracers both biased and unbiased (though I have never cycles) It must be possible to fix this.

T.

What about this picture?

[TBFX]

Hi Karba and Roeland,

Sorry my original post does seem a bit harsh, I was just quite surprised when I thought this issue had been put to one side as not able to be fixed, however after the responses I received this doesn't seem to be the case. I'm fine with it being a particularly difficult problem so long as it is being worked on or at least thought about on a regular basis as it really is a major artifact in certain situations.

I have only ever evaluated v-ray and never really used it in anger but the results below are what I got between Octane and V-ray using the same bump map (image based) on the same sphere, in the same Maya scene, they each used a plain grey shader and the physical sky/sun native to the renderer being used. V-ray was set to Brute Force for both primary and secondary bounces.

Not being well versed in V-ray I'm sure I'm missing something here but try as I might I could not replicate the issue in my V-ray renders.

Octane Render

V-Ray Render

T.