Portal lights

[alexos]

I don't get them. The manual says they're geometry - but how do I tell Octane to use my geometry as a portal light? And conversely, what's the light type-portal for? If I add one all settings are ghosted and, in my scene, it doesn't seem to do anything much. What am I missing here?

ADP.

[UnCommonGrafx]

It gives the render a "path" through which it can render a window or other such hole in some geometry. Makes the engine, I surmise, not have to figure out how to get/read rays through geometry making it work more efficiently.
Nodally, I tend to mix a portal and the material I want to show on the wall. In this way, I get the look and the more efficient effort of the render engine.

[alexos]

Hmm, then the "portal" light type is indeed useless?

ADP.

[juanjgon]

There is a material to define any geometry as portal lights. They work only with path tracing or PMC kernels. Anyway I never use them, so I am not sure about it's performance.

-Juanjo

[Rob49152]

I've found the portal light to be very useful. In one scene I did I used a sligtly curved surface with an image mapped to it outside of a window. Of course this alone did not give me the lighting I required. So I used the Sky render target and set it up to match the colour and approximate angle of the sun that I needed.

Since I used an image mapped to a polygon outside the window this blocked the sky render target. So I added the light portal to a surface the same shape at the window (an archway) placed it just i bit infront of the window facing inside and tada skylight flooding into the room.

worked perfectly. I also imagine that rendering light through a large glass surface would have slown the render down quite a bit.