[H13, Mantra] How to obtain light passes(direct&indirect)

[PaulM3D]

Greetings!

So, my question sounds like this: "How to obtain light passes(direct&indirect irradiance) in Mantra PBR?". I'm trying to do this a lot of time, so I think that I'm doing something wrong way.

Direct Irradiance(raw light?) - just direct grayscale light pass from light source like point, area or sun light.

Indirect Irradiance(maybe you can call it bounce light) - non-grayscale pass from environment or sky light. So, it must be light pass from environmental source.

So, basically I need "Direct Illumination" and "Indirect Illumination" in Maya terminology.

 

I'm new in Houdini shading and rendering. Could you please help me with my question? Can you explain me step-by-step, how I should choose type of light, configure them, how I should configure Mantra(PBR) render node and maybe shader? I tried to dive inside Mantra Surface material, but I have got some fake results.

 

[ADD] Maybe I can make direct light pass that way: [direct_diffuse] - [direct_color_noshading] ? Will try it now. [LATER] Nope, it doesn't work.

[ADD] Example would be great, but I will appreciate all helpful information and every answer.

[ADD] All of this should be done in one render. Saved to EXR file as layers.

 

Would be well appreciate.

 

Thanks for your attention.

 

Yours respecfully,

Paul.

 

P.S. picture example from some Maya video, not mine.

Edited July 29, 2014 by PaulM3D

[SreckoM]

Us Extra image planes. Under Mantra ROP, Output tab, click + on Extra image planes to add new one, and under VEX variable dropdown choose whatever you need.

[PaulM3D]

Thank for answer. I'm using it. But default Mantra Surface Shader passes(in Extra Image planes) I don't see what I need. I've tried them all. 

So, what VEX variable should I use to obtain passes, that I need? I know about custom "Parameter" Export node, I am using it. Difficult is in obtaining that 2 passes.

[PaulM3D]

Ok, guys, I think I've figured it out by myself.

So, maybe it will be helpfull for someone.

- Direct Irradience(raw direct light) pass could be obtained by creating simple Lambert node right in your shader. Then export color or illumination channel into Parameter node.

- Indirect Irradience(raw global light) pass it's "dirrect_diffuse" Image Plane for your Global light source(such as SkyLight or EnvLight). Then divide result of this to "diffuse_no_shading" and that would be right.

 

Could be wrong in theory(or in practice), but worked for me and I've got the result I wanted. Thank for your attention.

I'm ready for some other ways to do that and discussion.