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The shadow line is jagged in Cycles
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Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.75

Blender Version
Broken: version: 2.83.0, branch: master, commit date: 2020-06-03 14:38, hash: rB211b6c29f771
Worked: (newest version of Blender that worked as expected)

Short description of error
Eevee vs Cycles (Shade smooth is activated).
It's been there for a long time.

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]

Event Timeline

NXSK (NXSK) added a subscriber: NXSK (NXSK).EditedJun 4 2020, 3:54 PM

I have the same issue

The sphere is subdivided by 10 times from a primitive cube and shaded smooth.
The lighting is very simple, just a HDR image.
But I still can see the light transition breaks between faces.

This looks like the shadow terminator problem to me. In 2.90 there will be an option to shift the terminator towards the light source, hiding the artifacts at the cost of energy conservation. See rBc7280ce65b856d26d6807c1b7a081ffc6311bfdc and D7634

@NXSK (NXSK)

Only one HDR image for light, primitive sphere with smooth shade, looks fine.
Make sure to use Catmull-Clark type instead of Simple type.

@NXSK (NXSK)

Only one HDR image for light, primitive sphere with smooth shade, looks fine.
Make sure to use Catmull-Clark type instead of Simple type.

No. This is nothing to do with the subdivision surface modifier. If the normal is smoothed, the shading from viewer angle should be smooth, without any light breakups.

I think it might be the problem that robert says. And this issue might be there for a long time.

Phil Bao (bao007fei) added a comment.EditedJun 4 2020, 4:52 PM

@NXSK (NXSK)

Only one HDR image for light, primitive sphere with smooth shade, looks fine.
Make sure to use Catmull-Clark type instead of Simple type.

No. This is nothing to do with the subdivision surface modifier. If the normal is smoothed, the shading from viewer angle should be smooth, without any light breakups.

I think it might be the problem that robert says. And this issue might be there for a long time.

For your situation, only one HDR for light. I tried and didn't see any light break problem. Maybe the texture is not perfectly seamless?
For me it only appears for built-in lights with low subdivision geometry.

This looks like the shadow terminator problem to me. In 2.90 there will be an option to shift the terminator towards the light source, hiding the artifacts at the cost of realism and lack of energy conservation. See rBc7280ce65b856d26d6807c1b7a081ffc6311bfdc and D7634

Good to know, Thanks:D

Hope it can be fixed completely someday without any extra options and costs.

@NXSK (NXSK)

Only one HDR image for light, primitive sphere with smooth shade, looks fine.
Make sure to use Catmull-Clark type instead of Simple type.

No. This is nothing to do with the subdivision surface modifier. If the normal is smoothed, the shading from viewer angle should be smooth, without any light breakups.

I think it might be the problem that robert says. And this issue might be there for a long time.

For your situation, only one HDR for light. I tried and don't see any light break problem. Maybe the texture is not perfectly seamless?
For me it only appear for built-in lights with low subdivision geometry.

My texture is procedual. Some simple material won't show this issue.

And I'm curious about my previous work: a game flash light with low poly counts. Without normal map it still looks fine. But a sphere with a procedual carbon weave, it looks ugly, even if it is subdivided, just the jagged "teeth" becomes denser.

I asked my friends about this issue. They say Radeon Prorender and Octane render have the same issue. I think this might be the problem of path tracing shading algorithm.

Phil Bao (bao007fei) added a comment.EditedJun 4 2020, 5:21 PM

@NXSK (NXSK)

Only one HDR image for light, primitive sphere with smooth shade, looks fine.
Make sure to use Catmull-Clark type instead of Simple type.

No. This is nothing to do with the subdivision surface modifier. If the normal is smoothed, the shading from viewer angle should be smooth, without any light breakups.

I think it might be the problem that robert says. And this issue might be there for a long time.

For your situation, only one HDR for light. I tried and don't see any light break problem. Maybe the texture is not perfectly seamless?
For me it only appear for built-in lights with low subdivision geometry.

My texture is procedual. Some simple material won't show this issue.

And I'm curious about my previous work: a game flash light with low poly counts. Without normal map it still looks fine. But a sphere with a procedual carbon weave, it looks ugly, even if it is subdivided, just the jagged "teeth" becomes denser.

I asked my friends about this issue. They say Radeon Prorender and Octane render have the same issue. I think this might be the problem of path tracing shading algorithm.

I've never seen this problem beyond Cycles. Really weird.