On Thu, 27 Mar 2003 11:09:27 -0500, Jeff Baskin wrote:

> #include "colors.inc"
> #include "metals.inc"
> 
> /**************************************************
>  * Secret Laboratory Interior                     *
>  *                                                *
>  * Unit = 1 foot 				  *
>  *						  *
>  * It's on old army shed that has been converted  *
>  **************************************************/
>  
> light_source{
>   <0,1,0> 
>   color White
> }
> 
> light_source{
> 	<100,100,100>
> 	color White
> }
> 
> camera{
>   location <0,1,0>
>   look_at <50,5.5,0>
> }
> 
> #declare RAD=9;
> #declare LEN=50;
> 
> // Basic military hutch interior
> difference{ 
> 	isosurface{
> 		// This creates the corragated metal hull
> 		function{
> 			sqrt(pow(y,2)+pow(z,2))+(sin(atan2(z,y)*pi*RAD*6)/24)
> 		}
> 		threshold RAD
> 		contained_by{
> 			box{
> 				<0,-19, 0>, <LEN,19,19>
> 			}
> 		}
> 		open
> 		rotate <-90,0,0>
> 	}
> 	// Now create the opennings for the hutch
> 	// These are 1 x 2 holes in the wall.
> 	#declare Divisions = 10;
> 	#declare Space = ( LEN - ( Divisions * 2 ) ) / ( Divisions + 1 );
> 	#declare Count = 0;
> 	union{
> 		#while( Count < Divisions )
> 			box{
> 				<Space + Count * ( Space + 2 ),5,-20>, 
> 				<Space + Count * ( Space + 2 ) + 2,6,20>
> 			}
> 			#declare Count = Count + 1;
> 		#end
> 	}
> 	texture{
> 		pigment{ P_Chrome5 }
> 		finish{ F_MetalA }
> 	}
> }
> 
> plane{
>   y, 0
>   pigment{ checker Green White }
> }

The camera is inside the interior of the isosirface and your differenced 
boxed did cut holes in it. The only thing is that those holes were cut from 
the outside instead of the inside. Giving the isosurface an inverse tag 
does the trick and also fixes the hollow object warning (because the inside 
of the lab is no longer the interior of the iso. Here's my new code:

#declare RAD=9;
#declare LEN=50;
#declare Thickness = 1;

// Basic military hutch interior
difference{ 
        intersection{
        	isosurface{
        		// This creates the corragated metal hull
        		function{
        			sqrt(pow(y,2)+pow(z,2))+(sin(atan2(z,y)*pi*RAD*6)/24)
        		}
        		threshold RAD
        		max_gradient 1
        		all_intersections
        		contained_by{
        			box{
        				<-1,-(RAD+Thickness), -1>, <LEN+1,RAD+Thickness,RAD+Thickness>
        			}
        		}
        		rotate <-90,0,0>
        		inverse
        	}
        	cylinder{
        	        0, (LEN)*x, RAD+Thickness
        	}
        }
	// Now create the opennings for the hutch
	// These are 1 x 2 holes in the wall.
	#declare Divisions = 10;
	#declare Space = ( LEN - ( Divisions * 2 ) ) / ( Divisions + 1 );
	#declare Count = 0;
	union{
		#while( Count < Divisions )
			box{
				<Space + Count * ( Space + 2 ),5,-20>, 
				<Space + Count * ( Space + 2 ) + 2,6,20>
			}
			#declare Count = Count + 1;
		#end
	}
	texture{
		pigment{ P_Chrome5 }
		finish{ F_MetalA }
	}
}

PS. I've also added some thickness to these windows (which can be 
controlled) and given the isosurface all_intersections to avoid missing 
surfaces in CSG.

-- 
light_source#macro G(E)sphere{z+E*y*5e-3.04rotate-z*E*6pigment{rgbt#end{
20*y-10#local n=162;1}#while(n)#local n=n-.3;G(n)x}}G(-n).7}}#end//GregE

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