Procedural texture final render different from viewport

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Procedural texture final render different from viewport

Postby Philstix » Sat Feb 03, 2018 12:26 am

I'm using LuxCore (lux-opencl_linux64_18-12-2017) in Blender 2.79 on Xubuntu 16.04 to do a bidirectional render of node-based metal materials that are mostly using procedural textures, with a few math nodes involved. I used the Blender viewport render to get the textures about how I want them, but when I ran a final render I discovered a problem.

The textures in the final render do not match the same textures in the viewport render. They're similar, but not the same. I've played around with this for a while and I haven't been able to find a way to make the renders match. The difference is consistent regardless of render resolution, render borders, camera placement... It's as if the procedural textures are calculated differently in the final render than in the viewport. My first wild guess would be some kind of rounding error, but I don't really have any idea.

I searched the forum but I couldn't find anything relevant. Are there known issues with procedural textures in LuxCore?

2018-02-03_16-45-38_rendered.png
Final render


2018-02-03_16-45-38_blender-viewport.png
Blender viewport render
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Re: Procedural texture final render different from viewport

Postby B.Y.O.B. » Sat Feb 03, 2018 2:17 am

We're developing a new addon from scratch, so LuxBlend is no longer supported unfortunately.
You can join the re-boot to try the new addon: viewtopic.php?f=12&t=13485

Anyway I would need a small test scene that reproduces the problem to help you.
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Re: Procedural texture final render different from viewport

Postby Philstix » Sat Feb 03, 2018 6:33 pm

Thanks for the reply. I was mainly just checking to see if there were any known problems with procedural textures in LuxCore.

I eventually discovered the reason for the discrepancy between the render and the viewport. The 3d mapping in my texture is set to 'Object'. It seems that there is a difference in how the viewport calculates the object origin for applying the texture. The viewport applies the texture to the object regardless of the object's translation, while the render requires any object location change to be applied.

I tested this conclusion with a simple scene containing three cubes using the same procedural texture. The centre cube is the original, and the cubes on either side are duplicates.

The cube on the left was moved and then had it's location applied. The viewport and the final render are the same for the left object.

The cube on the right was moved without it's location applied. The viewport applies the texture to the right cube exactly the same as the original object. The final render, however, does not.

2018-02-04_10-48-42_problem-demonstration-viewport.png
Blender viewport
2018-02-04_10-48-42_problem-demonstration-render.png
Rendered image
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Re: Procedural texture final render different from viewport

Postby B.Y.O.B. » Sun Feb 04, 2018 2:40 am

Thanks for the investigation. I could reproduce the problem in the new addon and created a bug report.
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