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

Posted: Sun Nov 03, 2019 1:12 pm
by 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? :o

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

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

Posted: Sun Nov 03, 2019 7:14 pm
by 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

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

Posted: Mon Nov 04, 2019 5:50 am
by 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 :o After fixing that I still got very low power but it was because there was nothing to light up nearby :D
Octane works greatly with Houdini also for arbitrary-shaped and partial light objects, just in case someone else has the same problem :mrgreen:

Antti