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.
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:
Luxrender glossy node for reference:
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
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.
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)
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)"