Glossy Shader Error using "Shade Smooth" on low polly objects or text #39496

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Joshua Zacharias · 2014-03-28T21:51:17+01:00

Joshua Zacharias commented

2014-03-28 21:51:17 +01:00

System Information
Windows 8.1
happens on all my machines. All machines are equipted with geforce 650 or better and use intel processors (i5 and i7 4th gen)

Blender Version
Broken in 2.69 and 2.7

Short description of error
Low Polygon meshes and text have a reflection error and don't reflect everywhere the glossy shader is applied.

Exact steps for others to reproduce the error

Create a cycles scene.
Add a low cylindar with 6 verticies.
Add only glossy shader set to 0 roughness.
add a large cube to with a checkers material to have something to reflect.
put on render viewport shading on and rotate around objects to see black areas not reflecting anything.

Text also causes the problem. Try letter T or E for example.
Problem gets fixed when you increase poly count.
However Subdividing text isn't ideal to ensure reflections work.
I have some pictures of the error in a post I made on blenderartists forum
http://blenderartists.org/forum/showthread.php?331108-Glossy-Shader-Error-on-smoothing-curved-surfaces

**System Information** Windows 8.1 happens on all my machines. All machines are equipted with geforce 650 or better and use intel processors (i5 and i7 4th gen) **Blender Version** Broken in 2.69 and 2.7 **Short description of error** Low Polygon meshes and text have a reflection error and don't reflect everywhere the glossy shader is applied. **Exact steps for others to reproduce the error** - Create a cycles scene. - Add a low cylindar with 6 verticies. - Add only glossy shader set to 0 roughness. - add a large cube to with a checkers material to have something to reflect. - put on render viewport shading on and rotate around objects to see black areas not reflecting anything. Text also causes the problem. Try letter T or E for example. Problem gets fixed when you increase poly count. However Subdividing text isn't ideal to ensure reflections work. I have some pictures of the error in a post I made on blenderartists forum http://blenderartists.org/forum/showthread.php?331108-Glossy-Shader-Error-on-smoothing-curved-surfaces

Joshua Zacharias commented

2014-03-28 21:51:17 +01:00

Changed status to: 'Open'

Joshua Zacharias commented

2014-03-28 21:51:17 +01:00

Added subscriber: @JoshuaZacharias

Bastien Montagne commented

2014-03-28 22:04:57 +01:00

Added subscriber: @mont29

Bastien Montagne commented

2014-03-28 22:04:57 +01:00

Please attach a simple .blend file demonstrating the problem…

Joshua Zacharias commented

2014-03-28 22:12:28 +01:00

Here is a sample I made demonstrating the error.
I also attached a quick render of it called glossy bug.png

I had made another example when I made a simple curved wall. Flat.jpg is the object with the Flat shading applied and the smooth.jpg is the same object with smooth shading applied to the object
glossy_bug.blend

![glossy_bug.png](https://archive.blender.org/developer/F83279/glossy_bug.png) Here is a sample I made demonstrating the error. I also attached a quick render of it called glossy bug.png I had made another example when I made a simple curved wall. Flat.jpg is the object with the Flat shading applied and the smooth.jpg is the same object with smooth shading applied to the object [glossy_bug.blend](https://archive.blender.org/developer/F83274/glossy_bug.blend) ![smooth.jpg](https://archive.blender.org/developer/F83275/smooth.jpg) ![flat.jpg](https://archive.blender.org/developer/F83276/flat.jpg)

Bastien Montagne commented

2014-03-28 22:18:05 +01:00

Thanks for the file (not sure this is a bug, though, will let Brecht decide!).

Brecht Van Lommel was assigned by Bastien Montagne

2014-03-28 22:18:20 +01:00

Joshua Zacharias commented

2014-03-28 22:24:36 +01:00

No problem, just want to help.

Please make sure to take note of the flat.jpg and smooth.jpg as it is a more direct example showing a before and after of what appears to be the bug.

Thanks again for all your work!

No problem, just want to help. Please make sure to take note of the flat.jpg and smooth.jpg as it is a more direct example showing a before and after of what appears to be the bug. Thanks again for all your work!

Brecht Van Lommel commented

2014-03-28 23:08:22 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2014-03-28 23:08:22 +01:00

Brecht Van Lommel commented

2014-03-28 23:08:22 +01:00

This is not considered a bug at the moment. The problem is that the "fake" smooth normals don't correspond to the actual geometry. This works ok in many cases but in this case the mismatch reveals itself.

There are some ways that this can be improved but that's on the todo list.

If you like to read the technical explanation for this it's here:
http://www.geekshavefeelings.com/x/wp-content/uploads/2010/03/Its-Really-Not-a-Rendering-Bug-You-see....pdf

This is not considered a bug at the moment. The problem is that the "fake" smooth normals don't correspond to the actual geometry. This works ok in many cases but in this case the mismatch reveals itself. There are some ways that this can be improved but that's on the todo list. If you like to read the technical explanation for this it's here: http://www.geekshavefeelings.com/x/wp-content/uploads/2010/03/Its-Really-Not-a-Rendering-Bug-You-see....pdf

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Glossy Shader Error using "Shade Smooth" on low polly objects or text #39496