I thought I'd run some tests to see how they differ.  Interesting thing I found - if
the
patches are inside a union, povray seems to default to type 1 bicubic patches even if
type
0 is specified.  The results I got were exactly the same for the two in that
situation.
Also worth noting is that both the parse and render times were shorter when a union
was
used.

I had to make the mesh files with xroads to convert dxf to pov.  I matched everything
just
like the patch versions.  I noticed the meshes using 4 polygons per patch were light
on
memory, then it occured to me that 4 u and v steps should be 16 polygons per patch.  I
think that's right.  I just included a smooth triangles version of that.  I don't even
have
time to sort through all this.  I hope this is useful to someone. :)

rabbit.pov

All at 800x600, AA 0.3

type 0 or 1 bicubic patches inside a union
u_steps 4 v_steps 4

Time For Parse: 12 seconds
Time For Trace: 37 seconds
Total Time: 49 seconds
Peak memory used: 67,108,949 bytes

type 0 bicubic patches
u_steps 4 v_steps 4

Time For Parse: 9 seconds
Time For Trace: 7 minutes 32 seconds
Total Time: 7 minutes 41 seconds seconds
Peak memory used: 35,724,760 bytes

type 1 bicubic patches
u_steps 4 v_steps 4

Time For Parse: 35 seconds
Time For Trace: 46 seconds
Total Time: 1 minute 21 seconds
Peak memory used: 181,006,624 bytes

type 2 bicubic patches (superpatch)
accuracy .01

Time For Parse: 9 seconds
Time For Trace: 38 seconds
Total Time: 47 seconds
Peak memory used: 37,254,497 bytes

Mesh using 4 polys per patch, plain triangles

Time For Parse: 4 seconds
Time For Trace: 22 seconds
Total Time: 26 seconds
Peak memory used: 3,783,826 bytes

Mesh using 4 polys per patch, smooth triangles

Time For Parse: 7 seconds
Time For Trace: 17 seconds
Total Time: 24 seconds
Peak memory used: 4,193,854 bytes

Mesh using 16 polys per patch, smooth triangles

Time For Parse: 31 seconds
Time For Trace: 19 seconds
Total Time: 50 seconds
Peak memory used: 15,950,598 bytes

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