Help!

I'm working with a large height field object, rendered at very very high 
resolution and am coming across a strange artifact when I enable smooth.  
Basically, I see darkened boxes instead of a smooth shading (I'm also 
losing a lot of detail).  

I've got enough resolution in my height field source image, as the 
terrain is reasonably well contoured and the non smoothed image doesn't 
show large jaggies.  (although it shows serious stepping, making it 
unusable).  

Anyone have any suggestions on what might be going on, solutions or 
workarounds?  Am I hitting some upper limit in significant digits or 
precision, or is this related to the normal flipping issue in 
heightfields?

I've tried generating a mesh from the source bitmap image using Wilbur, 
but that took a LONG time to parse and couldn't ever get the same level 
of detail as the heightfield.   It also didn't make proper normals, so 
it was faceted.  I've tried different formats for the source image, with 
no change.

here's a jpg of the effect:
http://home.pacbell.net/selmo/smooth.jpg

and the same image without smoothing:
http://home.pacbell.net/selmo/no_smooth.jpg

I'm using POV 3.5 windows beta 11. 

It's a 16bit 5000x5000 pixel TIFF source image for the height field, 
rendered at 20K x 10K pixels.  (yes, I've got good reasons for needing 
such high res.  :)   I've tried disabling the shadow in case it was the 
normal-edge issue, but that didn't help either.

height_field
{
  tiff "topo.tif"
  scale < 1.0 , 0.02 , 1.0 >     
  smooth     
  no_shadow
  texture
          {
           finish {specular 0.15 roughness 0.8 crand 0.10 }
           pigment
            {          
	           White 
            }
                     
        }  
}    

Help!

Thanks
Lars

Post a reply to this message