Nieminen Mika wrote:
> 
> Peter Popov <pet### [at] usanet> wrote:
> : Merge of spheres - the problems typical for the union of spheres are
> : avoided, but merge is really slow as is.
> 
>   Not really true. I wonder why this delusion persists.
>   See http://www.students.tut.fi/~warp/povVFAQ.html#csgspeed
> 
>   (Everyone keeps saying that merge is (always) a lot slower than union,
> but no-one has ever said why. Or even proved it.)

  I have the following script that shows the merge operation taking 2 times
longer than a union of the same objects. I did recieve similar results as
you did with the example you gave but this example obviously takes longer
though I cannot offer an explaination as to why.

 Rendered at 120x100 no AA
 union time:  min. 3  sec. 9
 merge time:  min. 6  sec. 21

 union {
 // merge {
  #declare A =  0;
  #while ( A < 10)
     #declare B =  0;
     #while ( B < 10)
        #declare C =  0;
        #while ( C < 10)
           box { -.5, .5
       pigment { rgbf .9}
                 translate<-5,-5,-5>
                 translate <0.99*A, 0.99*B, 0.99*C>
               }
        #declare C = C + 1;
        #end
     #declare B = B + 1;
     #end
  #declare A = A + 1;
  #end     
 }

global_settings { max_trace_level 85}

         camera { location<2.5,5,-15> look_at 0}
   light_source { <30,100,100> rgb 1}
   light_source { <-0,10,-200> rgb 1}
    background  { rgb 1}

-- 
Ken Tyler
  
mailto://tylereng@pacbell.net
http://home.pacbell.net/tylereng/links.htm

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