Model Forum / General / Railroads / June 2004

Actually I may have spoken too soon :) Digging out some good 'ole Trig I was able to figure out how to make a very nice looking curve using splines. The problem is, I want to basically extrude a spline, or complex CSG object (which serve as the rails on the track) along a splined path assuring that it does not distort along the curve. The examples from the link squashed the isosurface as it moved along.

The code I have thus far is this (modified from an example in the Pov-Ray docs):
camera { location <0,4,0> look_at 0 }
                                                                               
light_source { <-5,30,-10> 1 }
#declare MySpline =
 spline {
//    cubic_spline
//    quadratic_spline
   natural_spline
   #declare counter = 0;
   #while (counter < 2*pi/6)
       counter, <sin(counter), 0, cos(counter)>
       #declare counter = counter + pi/16;
   #end
 }
                                                                               
#declare ctr = 0;
#while (ctr < 10)
 sphere{
       MySpline(ctr),0.05
       pigment{ color<ctr, 1-ctr, 0> }
 }
 #declare ctr = ctr + 0.01;
#end
                                                                               

The sphere is of course the item I want to convert into a CSG object or a spline to extrude along the path. The reason, by the way, that I want to use CSG or a spline for the rails is that I can use that same definition for other track as well - of course using the technique for the curves I want to use I could do the same for the straight peices as well I suppose. In any case, I tried playing around with boxes and things but that produced screwy results :) I'm not quite sure how the spline fits in with the object definition, since you can just change 'sphere' to 'box' and it works.

Any ideas about how to do that?
Tim

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