View Full Version : How to approximate an area light with point or spot lights

08-20-2014, 12:10 AM
I have some questions about area light:

1. In practice, is the light's intensity uniformly distributed across the surface?

2. How to sample an area light and how to approximate it with point or spot lights?


Agent D
08-20-2014, 12:53 AM
1. If by "in practice" you mean "in reality", no. If you mean in practical CG applications, it depends on the desired effect/realism. If
non-uniform distribution is not a must for one specific effect, it is easyer to assume uniform light distribution accross the surface,
especially if it has to be realtime (also, I don't think high frequence light fluctuations accross an area go that easy with radiosity)

2. In dynamic, real-time applications, you can approximate an area light with a point light if the distance is rughly 5 times the legnth of the
area. (rule of thumb, AFAIK this is from Realtime Rendering, 3rd edition). There are some hacks that try to "simulate" area lights in GLSL (http://www.gamedev.net/topic/552315-glsl-area-light-implementation/)

If you use lightmaps generated by offline lighting computations, static area lights should be no problem (especially if radiosity is used, which
only has area lights).