Hi all,

I have been playing around a bit with LPEs and I have run into a stumbling block. The issue is for a given light(Sphere or Env or Area) with “Render Light Geometry” enabled… is this considered as part of incandescent? As the default LPE VEX Variables of “lpe:CO”(direct incandescent) and “lpe:C.+O”(indirect incandescent) both return black AOVs for any given light that I have been testing. So, again is a given light considered part of incandescent when “Render Light Geometry” is enabled or is this a bug or am I missing something?

P.S. Using the default VEX Variables of direct_emission or indirect_emission in my ROP work but it does not allow me to split out two or more lights with “Render Light Geometry” into their own AOVs…


Thanks ahead of time for the help.


Kind regards,
Mark

Hi. Lights use “L” token. “O” refers to emissive objects, not direct light sources. To put contributions from one (or more) light into its own AOV, you need to assign an LPE tag to the light (look under light's parameter pane, look for “LPE Tag” parameter), and write an expression that ends with the light with the tag.

https://www.sidefx.com/docs/houdini/render/lpe.html [www.sidefx.com] has more information (search for ‘tag’. there are also example expressions that use tags.)

Good afternoon,

Thank you for the quick response… Just to clarify this topic, I have attached an image showing the results I am seeing. From what I understand when you enable “Render Light Geometry” on a light the output is incandescent(direct_emission) as you can see in the attached image. So, I just wanted to double check this as I am not getting the results I expected with the LPE and I think it could be a bug.

P.S. If this is not a bug then could you please kindly let me know what the LPE should be for this example.

Kind regards,
Mark

dlee
Hi. Lights use “L” token. “O” refers to emissive objects, not direct light sources. To put contributions from one (or more) light into its own AOV, you need to assign an LPE tag to the light (look under light's parameter pane, look for “LPE Tag” parameter), and write an expression that ends with the light with the tag.

https://www.sidefx.com/docs/houdini/render/lpe.html [www.sidefx.com] has more information (search for ‘tag’. there are also example expressions that use tags.)

Would the expression for all lights' direct rendering be lpe:CL?

@mwnorrie, as jsmack said, it should be “lpe:CL”.

I just tested this with mwnorrie, and it works fine in a vanilla Mantra ROP, but in a DNEG tainted Mantra ROP it fails.

So… it's a DNEG problem

Cheers,

Peter B

pbowmar
I just tested this with mwnorrie, and it works fine in a vanilla Mantra ROP, but in a DNEG tainted Mantra ROP it fails.

So… it's a DNEG problem

Cheers,

Peter B

tsk tsk, don't taint the rops