HowTo:Use macros and loops

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Loops

Loops are usually created to do one set of code thousands of times. The beauty of the loop is that the code can reference an array or a spline to write a rollercoaster track or a roadway such that very complicated scenes can be created with the use of simple structures.

Loops may be constructed through the use of the #while statement. A typical loop may be constructed as follows.

 #declare step = 0;
 #declare steps = 100;
 #while (step <= steps)
   #sphere { step*x, 0.4 pigment {Blue} }
   #declare step = step + 1;
 #end

Nested loops may be created to generate a two or three dimensional aspect to the scene. Beware that creating extra nested loops will dramatically increase the parse time for the scene.

The following nested loop will draw a series of Blue balls on the XZ plain

 #declare xpos = 0;
 #declare zpos = 0;
 #declare xfinal = 10;
 #declare zfinal = 10;
 #while (xpos <= xfinal)
   #while (zpos <= zfinal)
     #sphere { <xpos,0,zpos> 0.4 pigment {Blue} }
     #declare zpos = zpos + 1;
   #end
   #declare xpos = xpos + 1;
   #declare zpos = 0;
 #end