Thanks. 

It ended up with a little over half the objects in the rays. I used sphere
sweeps at first which was terrific for memory and appearance, but even with
Massimo Valentini's performance improvements to the sphere sweep code, it was
really slow. By the way, there are just over 4000 actual rays. I changed to
cones and spheres which helped the performance greatly, but to get a smooth look
I had to use a lot of them!!! 

I'll mention too that this image could be done with fewer objects by figuring
out what is hidden and dropping or simplifying those objects. However, I have in
mind the idea of doing grass with prisms in general and was in part getting a
feel for the limits of POV-Ray in this area.  

The advantage of polygons and prisms for things like grass is that you can stick
a lot of geometry into a small space. I have even put up to 2500 'polygons' into
one prism statement and been able to render it, but as you increase the number
this way the performance drops dramatically. I have yet to look at the source
for polygons and prisms, but I would guess there is not automatic bounding
within the objects and POV-Ray is doing an intersection test for each sub prism
in the prism statement.   

Anyway. just a rough idea for grass with prisms at this point.

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