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View Full Version : Area Light Bug or Feature?



Lord Dubu
03-08-2004, 02:37 PM
what you see HERE (http://studiozion.com/arealight.avi) is a test render demonstrating a frustrating property of an area light I'm trying to use to fake radiosity.

The light won't be animated in the final scene, it's just supposed to simulate light bounced off the table's surface normal.

In the test animation (linked above) I moved the light 2 feet away from the table over the span of 20 frames. As you can see, as the light gets further away from the surface normal, the more it seems to effect the table...

Anyone know what's happening here?

Lord Dubu
03-08-2004, 03:28 PM
http://www.studiozion.com/images/wip/arealight_bug.jpg

I should add that this is also happening for point lights. It's almost as if falloff has some how reversed itself.

mkiii
03-08-2004, 04:45 PM
It seems that this is just the way they work.

Try doing the same with a point light. If the light is close to the surface, it creates a small spill of light & a bright hotspot, leaving the majority of the area only slightly illuminated.

An area or Linear light works like that too, but spread out.

You can get around this by setting the Falloff/nominal distance to some high figure, say 100m or more for an object that size. This will make the light get to full brightness almost immediately, so the brightness between the light at 2cm above the table and at 2m will look pretty much the same.

Try using Inverse Distance ^2 with this sort of setting - the other falloff types will probably require a higher falloff.

Lord Dubu
03-08-2004, 05:13 PM
OK I'll play around with it when I get home, thanks for the input.

Matt
03-09-2004, 02:24 AM
mkiii is correct, setting falloff to inverse distance sorts out that problem, I fell for that one too!