Bump Mapping via Displacement input with OSL Doesn't Work #36368

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Nathaniel Winckler · 2013-08-04T00:40:35+02:00

2013-08-04 00:40:35 +02:00

%%%--- Operating System, Graphics card ---
Mac OS 10.8.4 - AMD Radeon HD 6750M

- Blender version with error, and version that worked ---

Blender 2.68a. I don' think any other version works. I only tried it out with 2.68a and 2.67b.

- Short description of error ---

Bump mapping via the Displacement input on the Material Output node does not work with an OSL shader. Maybe it is supposed to be this way, but it just seems kind of odd.

- Steps for others to reproduce the error (preferably based on attached .blend file) ---

Turn on Open Shading Language in the Render settings. Create a simple OSL shader in Blender (I just created a diffuse(N) shader) as you can see in the attached file. Connect the BSDF output of that to the input on the Material Output node. Now connect a texture to the Displacement input on the Material Output node. No bump mapping shows up (the only reason that I can think that this wouldn't work is that the Normals are being affected by the OSL shader...but unless I'm doing something completely wrong, I can't get that to look anywhere near as nice as when I just connect something to the Displacement input). To show that Bump mapping works otherwise, disconnect the OSL shader and just connect a Diffuse Shader to the Material Output. There should be bump mapping now. (One thing to note: True Displacement works with OSL when the Experimental feature set is turned on).
%%%

%%%--- Operating System, Graphics card --- Mac OS 10.8.4 - AMD Radeon HD 6750M - Blender version with error, and version that worked --- Blender 2.68a. I don' think any other version works. I only tried it out with 2.68a and 2.67b. - Short description of error --- Bump mapping via the Displacement input on the Material Output node does not work with an OSL shader. Maybe it is supposed to be this way, but it just seems kind of odd. - Steps for others to reproduce the error (preferably based on attached .blend file) --- Turn on Open Shading Language in the Render settings. Create a simple OSL shader in Blender (I just created a diffuse(N) shader) as you can see in the attached file. Connect the BSDF output of that to the input on the Material Output node. Now connect a texture to the Displacement input on the Material Output node. No bump mapping shows up (the only reason that I can think that this wouldn't work is that the Normals are being affected by the OSL shader...but unless I'm doing something completely wrong, I can't get that to look anywhere near as nice as when I just connect something to the Displacement input). To show that Bump mapping works otherwise, disconnect the OSL shader and just connect a Diffuse Shader to the Material Output. There should be bump mapping now. (One thing to note: True Displacement works with OSL when the Experimental feature set is turned on). %%%

Nathaniel Winckler commented

2013-08-04 00:40:35 +02:00

Changed status to: 'Open'

blender-admin commented

2013-08-04 00:40:35 +02:00

#42051 was marked as duplicate of this issue

Thomas Dinges commented

2013-08-04 14:33:14 +02:00

%%%Confirmed, assigning to Brecht. I quickly checked, but couldn't find the problem. %%%

Brecht Van Lommel commented

2013-08-06 07:48:27 +02:00

%%%It's a known issue actually, custom OSL shader scripts will not work with bump mapping at the moment. The reason is that the global N is no affected by bump mapping, instead we pipe the bumped normal into the Normal inputs in the existing shaders, but there's no way for custom scripts to do that.

I'll look into a solution, probably will need to split the generated OSL shader in separate bump and shading parts so we can modify N, as it's currently not possible to do that reliably from OSL code.%%%

%%%It's a known issue actually, custom OSL shader scripts will not work with bump mapping at the moment. The reason is that the global N is no affected by bump mapping, instead we pipe the bumped normal into the Normal inputs in the existing shaders, but there's no way for custom scripts to do that. I'll look into a solution, probably will need to split the generated OSL shader in separate bump and shading parts so we can modify N, as it's currently not possible to do that reliably from OSL code.%%%

Brecht Van Lommel commented

2013-09-03 17:43:13 +02:00

%%%I'm going to move this to the todo list, this should be solved as part of a bigger displacement / bump refactor. For now the only way is to connected a Bump node to the custom OSL nodes.%%%

Brecht Van Lommel commented

2013-09-03 17:43:13 +02:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2013-09-03 17:43:13 +02:00

Brecht Van Lommel commented

2015-05-03 15:11:00 +02:00

Added subscribers: @bithunter64, @Sergey

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Bump Mapping via Displacement input with OSL Doesn't Work #36368