Bump map and geometry thickness

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marcatore
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Bump map and geometry thickness

Post by marcatore » Thu Aug 02, 2018 2:32 pm

Hi,
I've m sharing a problem I've found when you have a bumped material (in this case a glossy material) applied to a geometry with no thickness.
bump_shading_issue.jpg
This is a comparison. Same material with same settings. I've just assigned a Solidify modifier to have thickness.
Is it correct when there is no thickness?

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B.Y.O.B.
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Re: Bump map and geometry thickness

Post by B.Y.O.B. » Thu Aug 02, 2018 2:45 pm

Maybe the normal of the surface without thickness is pointing away from the camera?

The glossy material has a weird legacy behaviour where the backside behaves like matte, only the front side (where the normal points) has the glossy coating. It is one of the things that should be changed when the material system is reworked.
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marcatore
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Re: Bump map and geometry thickness

Post by marcatore » Thu Aug 02, 2018 2:51 pm

I've just checked now and the normal direction is correct

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B.Y.O.B.
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Re: Bump map and geometry thickness

Post by B.Y.O.B. » Thu Aug 02, 2018 3:18 pm

In that case, maybe your objects are very large or very small, or you are using an extreme unit scale?
Or is there some large geometry in the scene, e.g. a huge ground plane?

Which engine are you using (OpenCL or CPU)?
Can you upload the scene, or make a smaller testscene that still shows the problem?
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marcatore
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Re: Bump map and geometry thickness

Post by marcatore » Mon Aug 06, 2018 10:23 am

The object is the floor of my scene I use to make the tests. It's that showroom with many lights on the ceiling.
You should already have it if you want to try it.
But you have to add by yourself a bump map.

In any case, the object has these measures
blender_2018-08-06_12-16-52.png
As engine, I'm using CPU path

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Dade
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Re: Bump map and geometry thickness

Post by Dade » Mon Aug 06, 2018 10:25 am

it may be a numerical precision problem due to too low thickness :?:
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Racleborg
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Re: Bump map and geometry thickness

Post by Racleborg » Mon Aug 06, 2018 11:33 am

I find that there must be a thickness that is at least the bump height.

Edited:

I should have said that I noticed this when the bump is in the Z- direction, as opposed to Z+. I presumed that this wasn't an actual error as you can't take something from nothing. :?: ;)

wasd
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Re: Bump map and geometry thickness

Post by wasd » Thu Aug 09, 2018 10:32 am

Something's wrong with bump.
~1000 samples cpu bidir+metropolis
Green point park 8k hdr from hdrihaven
Fabric 01 8k from cc0textures
Matte material
  • Bump, solid color
    bump-1.png
  • Bump, solidified mesh
    bump-3.png
  • No bump, color texture
    bump-2.png
  • No bump, solid color
    bump-4.png
  • Cycles bump
    bump-5.png
That loop-shaped structure – texture does not have anything like this, and this is just the most obvious strange thing, there's more.mp
CPU Bidir + Metropolis | Log Power | Core i5-4570

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