In article <3e12c8dd$1@news.povray.org>, "Mael" <mae### [at] hotmailcom> 
wrote:

> it also would be great to have an option to output an image as multiple
> layers , a layer for each kind of contribution : diffuse, highlights,
> reflection, refraction, radiosity, photons, media ..etc So we can do
> compositing in post process (blur a reflection, add glow only on highlights,
> increase radiosity brightness, and so on without the need to re render)

That would use huge amounts of memory, and I'm not sure how useful it 
would be. Using accumulation buffers would have big limitaitions, like 
only blurring things on objects seen directly. Storing the ray trees 
would use an impractical amount of memory...maybe in a decade, but by 
then we probably won't need such tricks.

A single precision float usually takes 8 bytes. Assume we are using 
those for everything, sacrificing some precision, a tree node is:

3 floats for ambient
3 floats for diffuse
3 floats for highlights (you could probably combine all types into this 
one color, I don't think separate values for different types would be 
useful)
3 floats for reflection
5(?) floats for pigment and transparency (assuming we keep the current 
system...I think we shouldn't.)
2 node pointers (8 bytes each) for transmitted and reflected rays (it 
could be many more, but I'll assume only two)
1 float for depth
3 floats for intersection point
3 floats for normal
3 floats for ray origin
3 floats for ray direction

30 floats and 2 pointers: 256 bytes for one node. The number of nodes 
possible is 2^max depth. At the default of 7, that's 128 nodes, or 32KB 
for one pixel sample. At 1024*768, that's 32MB a line, 24.6GB total. 
Assuming no antialiasing and a lot of reflective transparent shapes. If 
there is no transparency or reflection, only 192MB. And the overhead of 
managing all that would probably destroy any benefits, especially when 
using antialiasing.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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