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I have found many tutorials on PBR dielectric materials in cycles, but how do I do this in luxrender? In the past I would use a glossy material, but it handles roughness diffrently.

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I believe the Glossy material type in luxrender does what you want out of the box.

Unlike the glossy shader in cycles, the luxrender glossy material includes a "matte" component (diffuse in cycles-speak), making it loosely analogous to the following cycles setup:

enter image description here

Luxrender glossy node for reference:

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Render comparison

Cycles enter image description here

Luxrender enter image description here

I'm not really sure why the cycles render is dimmer than the luxrender example in this case. The difference appears to be in the diffuse part of things. If someone knows what's going on here, I'd definitely like to hear about it

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  • $\begingroup$ It looks like the difference between the two renders is actually due to the way the lamps are being interpreted $\endgroup$
    – gandalf3 ♦
    Sep 19, 2016 at 17:07
  • $\begingroup$ How do I convert the roughness from cycles to luxrender? $\endgroup$
    – SupaKoopaTroopa64
    Sep 25, 2016 at 22:19
  • $\begingroup$ @SupaKoopaTroopa64 In the luxrender glossy material, I believe the "Roughness" setting (separated into U-roughness and V-roughness in the properties panel) is equivalent to the roughness setting on the cycles glossy shader, and the "Sigma" setting is equivalent to the roughness setting on the cycles diffuse shader. $\endgroup$
    – gandalf3 ♦
    Sep 25, 2016 at 22:48
  • $\begingroup$ Oh, so these settingsmust be changed together. $\endgroup$
    – SupaKoopaTroopa64
    Sep 26, 2016 at 0:10
  • $\begingroup$ Well, diffuse roughness isn't linked to glossy roughness, no. I mentioned both, as I couldn't be sure which one you were referring to. $\endgroup$
    – gandalf3 ♦
    Sep 26, 2016 at 0:14
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What way is it not physically accurate? It is, and mostly follows the same conventions as realtime "diffuse/specular" PBR shaders. Just remember it uses "roughness" (shiny=0) while it somehow became a convention to use "glossiness" (shiny=1) with diffuse/specular. So just remember you need to diffuse, specular, roughness, and normal channels in a tool like Substance. Otherwise, you just plug in textures and go.

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First of all, I'm not trying to begin an argument, and sorry if I don't know how to post properly (I am a beginner at this). I attach six QUICK tests, and the source .blend file. They show how Luxrender image suffers from a "velvet" appearance on the very upper part of the ball, and the horizontal plane emitts light. Yafaray image is not very accurate since its glossy matterial cannot set ior properly (known behavior). See how Luxrender white carpaint is OK, but not editable. I would like somebody to show me a way to design a proper glossy material in Luxrender :( (I can send the blend file if somebody's interested)

enter image description here enter image description here enter image description here enter image description here enter image description here enter image description here

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    $\begingroup$ In the future please edit your answer, instead of adding new ones with more information. $\endgroup$
    – David
    Oct 12, 2018 at 17:41
  • $\begingroup$ Whoops, just saw this now. If you like, you can upload your blend here: blender.meta.stackexchange.com/q/630/599. I'm curious, did you control for tonemapping used by different engines or anything? $\endgroup$
    – gandalf3 ♦
    Oct 22, 2018 at 22:29
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I've been trying to create a phisically correct glossy material in luxrender for Blender for more than two weeks. Seriously, I'm nowhere near a beginner in photo-realistic rendering (I been working in this since good old POV-Ray 3.0 years :). I've tried every known way to achieve this task: glossy material, a matte base plus a glossy_coating, layered, car_paint, etc. To my astonishment, all of them lack the same excess of shine (in fact, there's a way: chosing one of the predefined car-paint shaders, which have no way to be edited -even color; if you swich to manual settings, the material fails). This is the real reason for the difference between Cycles (correct) and Luxrender (too bright). So, to my knowledge THERE IS ACTUALLY NO WAY TO ACHIVE A PHISICALLY CORRECT GLOSSY MATERIAL IN LUXRENDER. I know this is hard to believe, but sadly, after my thoroughly tests and comparisons with other engines (Indigo, Cycles, Mitsuba, and Yafaray). This is is my conclusion: "Lux glossy material is buggy: at shallow angles (object contours) it is not energy conserving (it reflects more light than it receives)"

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    $\begingroup$ Ok so you take a very low quality "answer" and turn it in to a wall of text rant. That's not going to help you. Your now deleted answer, was deleted because it did not even start to answer the question, it was not helpful enough to be converted to a comment and so a mod deleted it. How does "Lux glossy material is buggy: at shallow angles it is not energy conserving" help the OP make a PBR dielectric material in Luxrender? $\endgroup$
    – David
    Oct 12, 2018 at 14:06
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    $\begingroup$ Could you expand on your tests/comparisons with other engines, and/or how you know lux isn't conserving energy properly? I'd be interested learning the reason for this behavior too. $\endgroup$
    – gandalf3 ♦
    Oct 12, 2018 at 14:14

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