Paolo Berto


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Houdini Engine


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Shader lirary 2013年11月2日0:27

But did you know, when using PBR, you can layer an arbitrary number of surface model VOPS, using mix, add or whatever, with a very small cost in render time?

Yep, and I really like it.

This is a HUGE benefit to mantra, that BSDF models can be mixed so easily in VEX without a large performance hit, If you don't like the specular lobes you get from the built in bsdf models you can just layer several together to shape it the way you want. How many other renderers will allow this kind of free “bsdf sculpting”?

Yes, Mantra was actually the first commercial production grade renderer with such ability, to my knowledge.
More in general OSL solves this “by design” since you code in the renderer the BSDF and you don't do anymore light loops. Blender Cycles is able to do so and I believe Sony's proprietary Arnold supports it too. Appleseed can do it too but there is no shading language (yet). I am sure many others can be added to the list.

Shading language wise I expect this to be possible in RSL-based renderers: 3Delight's Path Tracer now has hardcoded BSDFs so as soon as you can avoid using illuminance() this will go to town. Same for PRMan.

As a long time lookdev artist, to me this is a ‘killer’ feature, and obviates the need for a multilayer node.

I was more referring at layering multiple materials each with a thickness and energy interchange, but in term of layering/shaping of specular yes this is absolutely cool.

Packed primitives information 2013年11月1日10:56

Thanks for the detailed info on the very same day of the release.

I am getting some amazing result on copy sop with packing before copying.


Shader lirary 2013年11月1日8:29

I disagree.

I am not going to build a house with a swiss knife

I'd use multiple tools. A general purpose shader is certainly good for many surfaces, definitely more than 50%, but not for everything. The best choice is use both a good general purpose one and very specialized shaders. Aside skin and fur, also physical metals, foliage, metallic paints, cloth, glass… and more. Layering also plays a big role in look development and sometimes you want energy to be accounted between layers, let's call this “physical-plausible layering” while some other times not (see layering in disney principled). Finally there is a component-based approach as you can see in Blender Cycles.

So, no “one shader to rule them all”: there is no single BxDF to handle everything. You do need a general purpose + multiple specialized shaders, using different bxdfs, and each of them depends on its own parametrization / UI / UX.