How to assing light to partial object (by group)?

[atnreg]

Hi!
I can get an object level object to act as light easily.
But how can I make say box that has top polygon as light and otherwise normal material?

I managed to make it emissive by using Diffuse material with Black body connected to emission input but the light power is very low, hardly notable.

It seems that I can only get real light from an object by using the object's Light emission tab but then the whole object acts as light so emissive materials would be useless. So I must be doing something wrong

Can somebody please give simple example (I'm new with Houdini too) how to make that box with top polygon as real light?

Please help me, thank you very much!

Antti

[juanjgon]

Hi,

Configuring emissive materials is easy. Check the attached image, where the cube has one face with an emissive material using the blackbody emitter node.

Thanks,
-Juanjo

[atnreg]

Thank you very much, that's basically how I tried to do it but for some reason my light power was very low, I'll need to check what I did wrong

EDIT: I did it right myself for Octane but made the material assignment wrong so totally my newbie mistake After fixing that I still got very low power but it was because there was nothing to light up nearby
Octane works greatly with Houdini also for arbitrary-shaped and partial light objects, just in case someone else has the same problem

Antti