Re: [Algorithms] lights/shadows rendering architecture

[Jon W. <hp...@mi...>]

> 3) 1 pass = n lights, shadow mapping done in scrreen space at the end
> This is a variation of 2). After the rendereing is done, i render a shadow

This will look as bad as the "darkening quad" way of doing stencil 
shadows. Back-facing surfaces will be darkened by the N dot L equation, 
and then again by the shadow map.

> How do you guys handle the lights and these typical problems ? What would be
> a reasonable number of lights casting shadows ?

You can get away with only sunlight casting shadows, if you don't need 
cinematic effects of actors moving in front of torches, etc. You can 
also reduce the cost of each pass by being stingy about what you 
actually render for each light -- cull at outer distances, prefer 
tighter spotlights, etc. Then let the artists make it run well enough 
for the look they get. (Contrary to popular belief, I've found that if 
the artists can get good, interactive performance tools and reports, 
they are quite capable of achieving reasonable frame rate)

However, "reasonable" depends a lot on your target hardware, scene 
composition, frame rate requirements, etc. On modern hardware (sm 3.0 
cards, etc) the cost of a single simple pass might not be as high as 
you'd think. Especially if you turn off RGB rendering and only render 
into depth.

Cheers,

			/ h+


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