"claudio56" <nomail@nomail> wrote:
> I'm looking for a way to 3d-print my povray image. It is indeed a very easy
> picture, consisting only of spheres and cylinders. As far as I could find, there
> is no direct converter from povray to the stl format (or any other format
> suitable for 3d printing). I hoped I could somehow import my cylinders and
> spheres with autocad, by I couldn't. The cylinders and spheres are generated
> (i.e. the coordinates are written) by another program but I can surely re-write
> them in an other format. So, is there a way to convert this easy set of objects
> into a 3d-print suitable format?

I have recently done exactly what you are seeking to do - output some spheres
and cylinders from a POV-Ray source file into an STL file suitable for 3D
printing. I used OpenSCAD, an open-source CSG modelling language, which creates
triangle models from geometric primitives described in a text file in a similar
fashion to POV-Ray.

http://www.openscad.org/

To achieve this, I wrote a couple of POV-Ray macros to create spheres and
cylinders in the OpenSCAD scene format. I've included them below, together with
some sample code to generate a file with a sphere and a cylinder. The macros
also include equivalent POV-Ray code to produce the same objects in a render so
you can check your geometry.

Simply run a render with this code, and the output .scad file should then be
usable in OpenSCAD. If you have a large number of objects it may take OpenSCAD
quite a while to perform the intersections, but I've not seen any errors yet. I
used it to create some polyhedron skeletons, which are very nice printed in
stainless steel :-)

Bill

NB you can change the triangle resolution with the $fs property - see the
OpenSCAD docs for more info.

------------------------------------------------------------------

#macro ScadCylinder(P1, P2, Radius)
 #local Len = vlength(P2-P1);
 #local Axis = vnormalize(P2-P1);
 // ---------- //
 // transform taken from Reorient_Trans() and Axis_Rotate_Trans() in
transforms.inc
 #local VX1 = z;
 #local VX2 = Axis;
 #local Y = vcross(VX1, VX2);
 #if (vlength(Y) > 0)
  #local VY = vnormalize(Y);
  #local VZ1 = vnormalize(vcross(VX1, VY));
  #local VZ2 = vnormalize(vcross(VX2, VY));
  #local Transform = transform {
    matrix <VX1.x, VY.x, VZ1.x,  VX1.y, VY.y, VZ1.y, VX1.z, VY.z, VZ1.z,  0, 0,
0>
    matrix <VX2.x, VX2.y, VX2.z, VY.x, VY.y, VY.z,   VZ2.x, VZ2.y, VZ2.z, 0, 0,
0>
  }
  #write (SCADFile, "translate([",P1.x,", ",P1.y,", ",P1.z,"])\n")
  #write (SCADFile, "multmatrix(m=[\n")
  #write (SCADFile, " [",VX2.x,", ",VY.x,", ",VZ2.x,", 0],\n")
  #write (SCADFile, " [",VX2.y,", ",VY.y,", ",VZ2.y,", 0],\n")
  #write (SCADFile, " [",VX2.z,", ",VY.z,", ",VZ2.z,", 0],\n")
  #write (SCADFile, " [0, 0, 0, 1]\n")
  #write (SCADFile, "])\n")
  #write (SCADFile, "multmatrix(m=[\n")
  #write (SCADFile, " [",VX1.x,", ",VX1.y,", ",VX1.z,", 0],\n")
  #write (SCADFile, " [",VY.x,", ",VY.y,", ",VY.z,", 0],\n")
  #write (SCADFile, " [",VZ1.x,", ",VZ1.y,", ",VZ1.z,", 0],\n")
  #write (SCADFile, " [0, 0, 0, 1]\n")
  #write (SCADFile, "])\n")
 #else
  #if (vlength(VX1-VX2) = 0)
   #local Transform = transform { }
   #write (SCADFile, "translate([",P1.x,", ",P1.y,", ",P1.z,"])\n")
  #else
   #local VZ = VPerp_To_Vector(VX2);
   #local AVX = vaxis_rotate(x, VZ, 180);
   #local AVY = vaxis_rotate(y, VZ, 180);
   #local AVZ = vaxis_rotate(z, VZ, 180);
   #local Transform = transform {
    matrix <AVX.x, AVX.y, AVX.z,  AVY.x, AVY.y, AVY.z,  AVZ.x, AVZ.y, AVZ.z,  0,
0, 0>
   }
   #write (SCADFile, "translate([",P1.x,", ",P1.y,", ",P1.z,"])\n")
   #write (SCADFile, "multmatrix(m=[\n")
   #write (SCADFile, " [",AVX.x,", ",AVY.x,", ",AVZ.x,", 0],\n")
   #write (SCADFile, " [",AVX.y,", ",AVY.y,", ",AVZ.y,", 0],\n")
   #write (SCADFile, " [",AVX.z,", ",AVY.z,", ",AVZ.z,", 0],\n")
   #write (SCADFile, " [0, 0, 0, 1]\n")
   #write (SCADFile, "])\n")
  #end
 #end
 // ---------- //
 cylinder {
  <0, 0, 0>, <0, 0, Len>, Radius
  transform { Transform }
  translate P1
 }
 #write (SCADFile, "cylinder(r=",Radius,",h=",Len,",center=false,$fs=0.02);\n")
#end

#macro ScadSphere(P, Radius)
 sphere {
  <0, 0, 0>, Radius
  translate P
 }
 #write (SCADFile, "translate([",P.x,", ",P.y,", ",P.z,"])
sphere(r=",Radius,",$fs=0.02);\n")
#end


#declare SCADFileName = "scad_file.scad";
#ifdef (SCADFile) #undef SCADFile #end
#fopen SCADFile SCADFileName write
#write (SCADFile, "// OpenSCAD generated by POV-Ray\n\n")

#write (SCADFile, "union () {\n")

union {
 ScadSphere(<0,0,0>, 5)
 ScadCylinder(<-10,0,0>, <10,0,0>, 2)
 pigment { rgb x }
 finish { ambient 0 }
}

#write (SCADFile, "}\n")

------------------------------------------------------------------

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