Sharp result with smooth shader

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lighting_freak
Posts: 93
Joined: Thu Jan 18, 2018 6:02 pm

Sharp result with smooth shader

Post by lighting_freak » Tue May 29, 2018 7:22 pm

Hi,

I'm trying to create a "moon-like" landscape.
Inside Blender the surface is nice smooth shaded:
Blender_appearance.JPG
The rendered image shows very sharp edges - exactly like the flat shaded edges:
the_moon.jpg
I guess I'm doing something wrong - but I dont know what:
This is my example file:
The_Moon.blend
(981.9 KiB) Downloaded 31 times
The background image can be downloaded from this URL (attached is a small *jpg ont to make the *blend workin):
http://hubblesite.org/image/4150/gallery

Thanks for your support.
BR
Attachments
stsci-h-p1821a-m-1699x2000.jpg
OS - Windows 7 X64
CPU - Intel CORE i7
GPU1 - Variants of notebook card from nVidia
GPU2 - Variants of notebook onboard card from Intel
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B.Y.O.B.
Developer
Posts: 1602
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
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Re: Sharp result with smooth shader

Post by B.Y.O.B. » Tue May 29, 2018 9:27 pm

It's the "terminator problem": An object that I set to "smooth shading" looks like it is shaded flat in shadow penumbras
It can not really be solved, you can only mitigate it.
For example, by subdividing the mesh further.
You should also try to use textures for the moon surface, they will help to hide the artifacts a bit.

By the way, some tips to improve rendering performance:
- Bidir is not needed in this scene, use Path with a low path depth (the defaults should be fine)
- Leave the lightgroup gain at 1, change the gain in the individual light settings instead.
I also noticed that you have a unit scale of 0.001, which causes the whole plane to be 1x1 meters small. Is this intended?

I added a subsurf modifier with level 2 to the mesh. It is still not enough to hide all artifacts.
Here is how the render looks with the mentioned modifications after 3 minutes of rendertime (CPU):
Attachments
the_moon.jpg
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B.Y.O.B.
Developer
Posts: 1602
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
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Re: Sharp result with smooth shader

Post by B.Y.O.B. » Tue May 29, 2018 9:45 pm

Here I have a simple gravel texture + normal map slapped onto the surface material.
The artifacts are still there, but are not so obvious immediately.

By the way, the terminator problem is something that most pathtracers struggle with, only a few renderers have workarounds for it that can reduce it when certain conditions are met.
"Terminator artifact treatment" placed 6th on the v2.1 feature poll: viewtopic.php?f=5&t=308
Attachments
the_moon_texture.jpg
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