Is there a standard OpenGL (ES3) shader I can drop in a GPLed application that uses a decent (is there a standard?) BRDF similar to Schlick with red,green,blue, and roughness?
I've wanted to add this capability to Solvespace for a while. I did my own implementation with the Fresnel term and it looked OK, but I want something "standard" and correct.
I think most realtime production uses something similar to Disney BRDF when they refer to PBR.
https://media.disneyanimation.com/uploads/production/publica...
I don't think there is a standard as such that would dominate the industry. It's all approximations to give artists parameters to tweak.
IMHO - Being an ex professional CAD person I think PBR is the wrong visual style for most cad though. The main point of shading is to improve the perception of shape and part isolation there. Traditional airbrush based engineering illustration styles are much better reference. So something like Gooch with depth buffer unsharp masking IMHO would be much much more appropriate.
>> Being an ex professional CAD person I think PBR is the wrong visual style for most cad though. The main point of shading is to improve the perception of shape and part isolation there. Traditional airbrush based engineering illustration styles are much better reference. So something like Gooch with depth buffer unsharp masking IMHO would be much much more appropriate.
That is some excellent feedback. I like that our current simple Snells law shader doesn't add specular highlights and can do flat shading by turning off all but the ambient light. I had never heard of "Gooch" and I don't recommend searching for it without "Gooch in the context of rendering". That looks interesting and we already have code to draw the silhouette edges.
I do think adding a PBR based Fresnel component with a backlight gives a similar but less sharp delineation of edges of objects, but it tends toward white right on the edge.
While people like a good PBR render, I agree that in CAD the objective of the rendering is to clearly convey the geometry AND the sketching tools and entities the user is manipulating.
You might find value in the glTF sample renderer https://github.com/KhronosGroup/glTF-Sample-Renderer
It won't be plug and play since you'd have to pull out the shaders and make them work in your app, but the implementation supports quite a few material variants. The PBR shader implementation starts in source/Renderer/shaders/pbr.frag
Even if you have a standard specular & diffuse model, indirect lighting is really important and you can't really just drop that into a shader.
If you want a standard I've go with OpenPBR, it is well documented and looks nice. Just skip the extra layers to begin with(fuzz/coat etc).
There is no standard.
Filament is extremely well documented: https://google.github.io/filament/Filament.html
glTF's PBR stuff is also very well documented and aimed at realtime usage: https://www.khronos.org/gltf/pbr/
OpenPBR is a newer, much more expensive BRDF with a reference implementation written in MaterialX that iirc can compile to glsl https://academysoftwarefoundation.github.io/OpenPBR
Pick one of the BRDFs, add IBL https://bruop.github.io/ibl, and you'll get decent results for visualization applications.