Area light cheating

[Matt Sheppard]

Ok.. go ahead and blast me for my cheat here, but it does seem to improve my rendering times.. However I am getting some side effects I hope you can help me with..

 

Notice the can lights in my quick ceiling detail, they are holes cut below a simple area light rectangle.. The problem is that even though the rectangle is above the solid that makes up the ceiling, you can see the edges of the area light. You might have to zoom in to see it, but it's happening on the closest grid of lights. Also, the lines you see seem to radiate from the quadrants of the lights vs the actual dimensions of the light source above.

 

Don't critique my rendering too much.. It's in it's infancy and I am just playing with lighting. But go ahead and critique/discuss the idea of 1 area light vs. 4 omni lights.

 

Thank you!

Matt

[Roy Hirshkowitz]

The rendering is fine.  

Cutting little round holes in a large area light is very creative but borderline idiotic.  It's probably only working at all because something has gone very wrong here.  It's likely the same thing that's causing the artifacts and quite likely a precision problem.  For some reason the solid in front of the rectangular source is not able to reliably obscure the source in the opaque areas.  This is liklely due to incorrect drawing units, the drawing being located too far from the origin, or the two surfaces being too close together.

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In any case, once you get it to work right, your rendering times will go way up.  Think of it this way-- nXt randomly locates points on a light source to use during each pass.  In your case, the chance of one of these points being obscured is probably about 98%.  That means that only 2% of the samples will do anything useful.

 

If you can't figure it out, upload the drawing and I'll take a look.