Shaders produce different results when OSL is enabled #43777

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Fred Rothganger · 2015-02-22T15:41:28+01:00

Fred Rothganger commented

2015-02-22 15:41:28 +01:00

System Information
Fedora Core 21
GTX580 (not in use, all CPU rendering)

Blender Version
Broken: 2.73a bbf09d9
(Has been broken in a number of previous versions, at least since 2.69)

Description of error
The attached Leaves.blend is part of a tree. Set viewport shading to "Rendered". At a distance (as posed in the file) the foliage looks darker (more correct) with the "Open Shading Language" box unchecked in Render settings. With OSL checked, everything comes out brighter. When zoomed in, they look about the same, suggesting some pixel quantizing is part of the effect. Looking very close, you see that the edges of the leaves are brighter in the OSL enabled state.

It may be that trimming back the alpha mask will correct this. Tried cleaning it up a little, but no improvement yet. However, the surprising part here is that enabling OSL makes a difference. Tried to simplify this down to just the Mix Shader, but the problem is not so evident as when the "fac" input is provided by the mask file. There is some noticeable difference when fac is fixed at 0.5.

**System Information** Fedora Core 21 GTX580 (not in use, all CPU rendering) **Blender Version** Broken: 2.73a bbf09d9 (Has been broken in a number of previous versions, at least since 2.69) **Description of error** The attached [Leaves.blend](https://archive.blender.org/developer/F145269/Leaves.blend) is part of a tree. Set viewport shading to "Rendered". At a distance (as posed in the file) the foliage looks darker (more correct) with the "Open Shading Language" box unchecked in Render settings. With OSL checked, everything comes out brighter. When zoomed in, they look about the same, suggesting some pixel quantizing is part of the effect. Looking very close, you see that the edges of the leaves are brighter in the OSL enabled state. It may be that trimming back the alpha mask will correct this. Tried cleaning it up a little, but no improvement yet. However, the surprising part here is that enabling OSL makes a difference. Tried to simplify this down to just the Mix Shader, but the problem is not so evident as when the "fac" input is provided by the mask file. There is some noticeable difference when fac is fixed at 0.5.

Fred Rothganger commented

2015-02-22 15:41:28 +01:00

Changed status to: 'Open'

Fred Rothganger commented

2015-02-22 15:41:28 +01:00

Added subscriber: @frothga

Fred Rothganger commented

2015-02-22 17:44:07 +01:00

The images were not embedded in the previous file, but they are important to reproduce the problem. Here is another attempt. Leaves.blend

The images were not embedded in the previous file, but they are important to reproduce the problem. Here is another attempt. [Leaves.blend](https://archive.blender.org/developer/F145280/Leaves.blend)

Fred Rothganger commented

2015-02-22 17:50:38 +01:00

Hmm. The problem does not reproduce in the second version I uploaded. This suggests either that the trimmed version of the alpha mask actually cleaned it up, or embedding the image changes the results, or that png works correctly but not jpg. Will study this a little more, and post something this afternoon.

Fred Rothganger commented

2015-02-22 20:39:57 +01:00

Best I can tell, the thing that makes a difference is whether the file is packed or not. Specifically, there are two variables:
Open Shading Language = enabled / disabled
blatt1_a.png = packed / unpacked

with these results
image packed

  OSL enabled -> normal color
  OSL disabled -> normal color

image unpacked

  OSL enabled -> too light, especially zoomed out (seems that edges dominate the render)
  OSL disabled -> normal color

Results appear to be the same with the JPEG version of the file. However, after packing the image, you must save and reload to see the effect.

Best I can tell, the thing that makes a difference is whether the file is packed or not. Specifically, there are two variables: Open Shading Language = enabled / disabled blatt1_a.png = packed / unpacked with these results image packed ``` OSL enabled -> normal color OSL disabled -> normal color ``` image unpacked ``` OSL enabled -> too light, especially zoomed out (seems that edges dominate the render) OSL disabled -> normal color ``` Results appear to be the same with the JPEG version of the file. However, after packing the image, you must save and reload to see the effect.

Fred Rothganger commented

2015-02-22 21:34:12 +01:00

It seems that both images (the leaf and its alpha mask) must be packed.

It seems that *both* images (the leaf and its alpha mask) must be packed.

Sergey Sharybin self-assigned this 2015-02-23 10:43:47 +01:00

Sergey Sharybin commented

2015-02-24 10:57:03 +01:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2015-02-24 10:57:03 +01:00

Sergey Sharybin commented

2015-02-24 10:57:03 +01:00

Did some investigation and wouldn't really consider this is a bug. The things are:

OSL does support texture mipmapping using OIIO
When images are packed, no OIIO is used, meaning no mipmaps could be used
Mipmaps could really affect on the edges in this case, because they're like blurring the texture
SVM does not support mipmaps at all

This explains the difference in setups you're comparing and those difference are not caused by any bug actually. Supporting mipmaps for SVM is in our TODO list. So thanks for the report, but closing as TODO now.

Did some investigation and wouldn't really consider this is a bug. The things are: - OSL does support texture mipmapping using OIIO - When images are packed, no OIIO is used, meaning no mipmaps could be used - Mipmaps could really affect on the edges in this case, because they're like blurring the texture - SVM does not support mipmaps at all This explains the difference in setups you're comparing and those difference are not caused by any bug actually. Supporting mipmaps for SVM is in our TODO list. So thanks for the report, but closing as TODO now.

Fred Rothganger commented

2015-02-24 14:45:07 +01:00

This sound like a pretty good explanation for the quantizing effect. However, I only see the color problems when the images are not packed. Your explanation would lead me to the opposite expectation.

This sound like a pretty good explanation for the quantizing effect. However, I only see the color problems when the images are *not* packed. Your explanation would lead me to the opposite expectation.

Sergey Sharybin commented

2015-02-24 18:00:36 +01:00

Not sure why it'll lead to opposite expectation...

Bright colors are only happening when mipmaps are used. And mipmaps are only used:

When OSL is enabled
When loading happens via OIIO

When OSL is getting enabled is pretty much straightforward :) Now, when OIIO is used in any cases BUT:

Movie files
Packed images

Don't see conflicts with my previous explanation tbh but would be happy to re-phrase it if it's still not totally clear :)

Not sure why it'll lead to opposite expectation... Bright colors are only happening when mipmaps are used. And mipmaps are only used: - When OSL is enabled - When loading happens via OIIO When OSL is getting enabled is pretty much straightforward :) Now, when OIIO is used in any cases BUT: - Movie files - Packed images Don't see conflicts with my previous explanation tbh but would be happy to re-phrase it if it's still not totally clear :)

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Shaders produce different results when OSL is enabled #43777