Hello,

I am having an issue in Houdini 15 (latest Build 15.0.347) where the Geo Light is not emitting light when I give it a material. I have found a couple possible problem areas, but still do not understand what the real issue might be that's causing this.

I have it set up so that the Geo Light is using a grid object, as well the same material as that grid (glowing cracks), to emit the light. When I render though the light is not being emitted onto the sphere. I have tried messing with the intensity/exposure, as well as attenuation, to make sure it wasn't just too dim to see. Still nothing.

I have tried using both Ray Tracing and PBR rendering engines and neither work until I uncheck “Ray Variance Anti-aliasing.” With that unchecked though, if I check the “Transform Into This Object” check box it stops emitting light again. If I uncheck the “Transform Into This Object”- check box though it emits light. With “Ray Variance Anti-aliasing” on it does not work whether the “Transform Into This Object” check box is checked or not. So I am wondering if anyone here may have an idea of what might be going on here? Any help or insight you can provide is appreciated. Thanks

I think GEO light is supposed to be used as geo only. That means if you want a light to be shaped like your geometry convert it into a geo light.

Material emission is another technique. That is where you use the material to generate light.

It sounds like you are trying to both on the same object. Don't do that. Make a separate copy of the grid and place your emission material on that copy of the grid then remove the previous emission material from the geo light copy of the grid.

If you post your scene, I'll take a look.

To make a geometry light with a material Your Material needs the emission (emit_clr) for the geometry light to read it.

1. make your geo light
Check Render Light Geometry and transform into this object depending on your pref.

2. setup material to the surface model connect emission texture to emit_clr
3. select your material under Material in the Area Light Options tab on your geolight.
4. should work

if you need an example file let me know i can put something together if it doesnt work.