Re: Lights (was Re: 64 bit version of Quesa)

[James W. <ja...@fr...>]

Roger Holmes wrote:

>> In answer to the question "why do they have to be known before
>> StartRender time", my answer is: because any OpenGL-based renderer  
>> needs
>> to have the lights set up before you render anything that should be  
>> lit
>> by said lights.
> 
> Well if that is a restriction of OpenGL then fair enough. I just  
> think that no processing of lights can be done until a (non shadow)  
> renderer has the Z buffer set up with depths and references to the  
> triangles, and whilst the renderer builds the list of triangles (and  
> culls some) it could have set up the list of lights whilst it parsed  
> the group structures.

Either I'm misunderstanding you, or you have a mental model of rendering 
that doesn't correspond to the way any of our built-in renderers work. 
There isn't any separate phase of setting up the Z buffer with depths 
and references to triangles.  There's a continuous process of breaking 
triangles into fragments, updating the Z and color buffers with new 
fragment data, and so on.  Once a particular triangle has passed through 
the pipeline, there is no opportunity to change the way it has been lit.
-- 
   James W. Walker, Innoventive Software LLC
   <http://www.frameforge3d.com/>