Cycles: Glossy at roughness 1.0 is different than Diffuse #37899

New Issue

Avenger · 2013-12-20T15:41:33+01:00

Avenger commented

2013-12-20 15:41:33 +01:00

System Information
Windows 7 64 bit, Nvidia Geforce GTX 760

Blender Version
Broken: Blender 2.69 r61157

Short description of error
Shouldn't glossy reflections at roughness 1.0 look exactly like Diffuse?
Currently I'm getting dark shades near the border and slight shades in the center.

On the attached images, the sphere on the left is Diffuse, the right one is glossy.
(the lighter image is Beckmann, the second one GGX)

Exact steps for others to reproduce the error
Render the attached .blend file.GlossBug.blend

**System Information** Windows 7 64 bit, Nvidia Geforce GTX 760 **Blender Version** Broken: Blender 2.69 r61157 **Short description of error** Shouldn't glossy reflections at roughness 1.0 look exactly like Diffuse? Currently I'm getting dark shades near the border and slight shades in the center. On the attached images, the sphere on the left is Diffuse, the right one is glossy. (the lighter image is Beckmann, the second one GGX) **Exact steps for others to reproduce the error** Render the attached .blend file.[GlossBug.blend](https://archive.blender.org/developer/F46918/GlossBug.blend) ![GlossBugBeckmann.jpg](https://archive.blender.org/developer/F46919/GlossBugBeckmann.jpg) ![GlossBugGGX.jpg](https://archive.blender.org/developer/F46921/GlossBugGGX.jpg)

Avenger commented

2013-12-20 15:41:33 +01:00

Changed status to: 'Open'

Avenger commented

2013-12-20 15:41:33 +01:00

Added subscriber: @OskarSwierad

Bartosz Moniewski commented

2013-12-20 15:55:53 +01:00

Added subscriber: @BartekMoniewski

Brecht Van Lommel commented

2013-12-20 15:57:27 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2013-12-20 15:57:27 +01:00

Brecht Van Lommel self-assigned this 2013-12-20 15:57:27 +01:00

Brecht Van Lommel commented

2013-12-20 15:57:27 +01:00

No, there is no fixed rule that says they should be the same. You can make a roughness based diffuse-glossy mix shader if you want this behavior.

Avenger commented

2013-12-20 16:22:42 +01:00

Hey, it's not so irrelevant.
In Marmoset Toolbag it works that way:

Thanks to this, I can use the whole scale of bluriness using a single gloss map.
Using Mix shader between sharp reflections and diffuse wouldn't give me this effect.

Hey, it's not so irrelevant. In Marmoset Toolbag it works that way: ![Marmoset.jpg](https://archive.blender.org/developer/F46925/Marmoset.jpg) Thanks to this, I can use the whole scale of bluriness using a single gloss map. Using Mix shader between sharp reflections and diffuse wouldn't give me this effect.

Brecht Van Lommel commented

2013-12-20 16:46:26 +01:00

I'm not saying it's irrelevant, I know this behavior is useful. But we implement a particular BSDF model that has some set of properties and trade-offs.
http://www.cs.cornell.edu/~srm/publications/EGSR07-btdf.pdf‎

Ok, you want a different behavior, and we could implement it at some point. But that doesn't make it a bug, it's a feature request.

I'm not saying it's irrelevant, I know this behavior is useful. But we implement a particular BSDF model that has some set of properties and trade-offs. http://www.cs.cornell.edu/~srm/publications/EGSR07-btdf.pdf‎ Ok, you want a different behavior, and we could implement it at some point. But that doesn't make it a bug, it's a feature request.

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Cycles: Glossy at roughness 1.0 is different than Diffuse #37899