Hi there.

I´m quite used to using passes for tweaking in comp, but I´m a bit overwhelmed by the number of passes available in Houdini and surprised by a couple of them (for instance refraction not appearing in direct passes).

For instance,

I´m used to something like this.

((Radiosity color*diffuse+diffuse shading)*RawRGB)+SSS+specular+reflection+refraction= Beauty.

I´ve found out what I called diffuse is called diffuse ray-level (fair enough), and specular and reflection passes come straight on from all-diffuse and all-reflect, and all-refract gives refraction.
I guess my puzzlement comes from how to handle GI and diffuse.

Specifically, where to get the GI color from and where is the diffuse shading without color to mix it with a raw RGB. And where is the raw RGB?


What is your usual approach?

On the other hand, having direct access to an SSS with single and multi scattering passes is wonderful. The unshadowed diffuse is pretty cool as well.

For my latest video I put on vimeo I exported the Direct and Indirect components per light (diffuse, reflect, coat, refract, volume) as well as Combined Emission (both single and multi SSS in my case). The way to comp these together is dead easy, just Plus them all together and you are good to go.

Netvudu
Hi there.

I´m quite used to using passes for tweaking in comp, but I´m a bit overwhelmed by the number of passes available in Houdini and surprised by a couple of them (for instance refraction not appearing in direct passes).

For instance,

I´m used to something like this.

((Radiosity color*diffuse+diffuse shading)*RawRGB)+SSS+specular+reflection+refraction= Beauty.

I´ve found out what I called diffuse is called diffuse ray-level (fair enough), and specular and reflection passes come straight on from all-diffuse and all-reflect, and all-refract gives refraction.
I guess my puzzlement comes from how to handle GI and diffuse.

Specifically, where to get the GI color from and where is the diffuse shading without color to mix it with a raw RGB. And where is the raw RGB?


What is your usual approach?

On the other hand, having direct access to an SSS with single and multi scattering passes is wonderful. The unshadowed diffuse is pretty cool as well.

((Radiosity color*diffuse+diffuse shading)*RawRGB)+SSS+specular+reflection+refraction= Beauty.

Doing that is incorrect everything needs to be plus because light is additive. Comp wise in Nuke you should be able to break out your passes and assemble the AOV's / image planes and they should match the beauty pin perfect.
In the production world I gave up rendering pure colour passes years ago and like wise unshadowed , also rendering a separate occlusion pass, when you get occlusion for free with the env light.
Everything is driven by your lights in the scene and in many cases that can be just a env light , key and fill lights. broken into the relevant passes.

Rob

Thanks guys. That´s very good info.

I will preach good comp practices from now on, now that I´ve seen the (additive) light…

Even though Mantra isn't listed, I found this helpful:
http://www.spherevfx.com/written-training/miscellaneous-written-training/multipass-rendering-and-compositing/ [spherevfx.com]

I guess Arnold comes closest, but as you can see the correct way is to add everything together. It doesn't have to be in any specific order as well.