How to approximate an area light with point or spot lights

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?


  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

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).