View Full Version : 9.5 area light > object Qs

Ernest Burden
10 October 2005, 07:53 PM
Something the manual does not cover--isues with using an object for an area light. It talks about it, but misses some things that are puzzling me:

Experimenting, it does not seem to matter where the area light is for the object to 'shine'. Is that true?

Also, what, if anything, does it matter about the overall size or orientation of the master area light?

In simple tests I'm getting great results, but in a real file I'm not, and I have a deadline and am stressed. Any advice would be appreciated!

10 October 2005, 06:56 AM
If you use an Area light with geometry asd actual light the light object itself has only an influence if you use other shadows then area shadows. Since Geometry Area lights can not use Hard or Softshadows these will be cast from the original lightsource.

10 October 2005, 07:04 AM
The obejct itself makes a difference too with object area lights, in terms of how the light is cast. Area lights work by creating a lot of lights over the surface (or in the volume) of the area. You will need to up the samples accordingly with a more comlex object with for instance multiple parts, or even use the "Add Grain" option in certain circumstances. Area lights are powerful but in certain situations it's faster to use GI and/or AO with an environment color.

Ernest Burden
10 October 2005, 12:56 PM
Since Geometry Area lights can not use Hard or Softshadows these will be cast from the original lightsource.

Thank you!

Perhaps that's where I'm having trouble--using soft shadows vs area shadows.

So if I use soft shadows I need to make the area light slightly larger than the object, and put its center in the spot I want as an 'origin' for the light, even though its an area?

Where this is being used is for groups of ceiling lights. Rather than set up a whole lot of lights, I wondered about just assigning geometry to be an area light, so they all shine down. Samples becomes an issue.

Another use, and this is what I was really puzzling with, was making a floor glow light upwards for a night shot from outside of a building. I have tried using a luminous material, and it works very nicely. But you cannot control the falloff and you cannot preview the effect with GI off. Using an area with geometry you can render it without GI to tweek your falloffs, so its a better process. But the glowing material does not seem to suffer 'samples' hotspots.

Any suggestions on which to proceed with? Anything I'm missing here? Using area light/geometry seems like a really powerful technique for architectural vis.

What about using a very small spline object for a light surface? Do the samples get forced along the spline length? That could really help.

CGTalk Moderation
10 October 2005, 12:56 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.