Peter Popov wrote:
> 
> Can anyone help me to solve the following problem: I know the coordinates of
> a cylinder and I want to map a radial y pigment on it. I want to define the
> texture at the origin and then translate it. Or define a unit cylinder and
> somehow fit it into the coordinates I have.

Perhaps something like the below file will fit your needs; the syntax
(after including the file) is as follows (note that standard brackets
() are used, not {} braces):

   Textured_Cylinder (<Base Point>, <Cap Point>, Radius, texture {...})

or:

   Textured_Disc (<Centre>, <Normal>, Radius, texture {...})

where the texture {...} is aligned as desired along the +y axis.  Other
shapes can be textured using the Fit_Texture_to_Cylinder macro, eg:

   cone {<-5, -4, -2>, 2, <5, 4, 1>, 1 open
      Fit_Texture_to_Cylinder (MyTexture, <-5, -4, -2>, <5, 4, 1>, 2)}

One thing to note - I've had to write out the second atan2 () function 
in the first macro in full (it looks as though the fix I sent the
POV-Team got somewhat lost in the translation!), to avoid the irritating
Domain Error crash.


// -- CylTex.inc -----------------------------

#macro Fit_Texture_to_Cylinder (cyltexture, point1, point2, cylradius)
   #local _CT_axis = (point2 - point1) * <1, 1, 1>;
   #if (vlength(_CT_axis) = 0) texture {cyltexture} #else
   #local _CT_rotx = degrees(atan2(vlength(_CT_axis * <1, 0, 1>), _CT_axis.y));
   #if (_CT_axis.x = 0) #if (_CT_axis.z >= 0) #local _CT_roty = 0; #else #local
_CT_roty = 180; #end
      #else #if (_CT_axis.z = 0) #if (_CT_axis.x > 0) #local _CT_roty = 90; #else
#local _CT_roty = -90; #end
         #else #local _CT_roty = degrees(atan2(_CT_axis.x, _CT_axis.z)); #end #end

   texture {cyltexture
      scale <cylradius, vlength(_CT_axis), cylradius>
      rotate <_CT_rotx, _CT_roty, 0>
      translate point1}
   #end
#end

#macro Textured_Cylinder (point1, point2, cylradius, cyltexture)
   cylinder {point1, point2, cylradius
      Fit_Texture_to_Cylinder (cyltexture, point1, point2, cylradius)}
#end

#macro Textured_Disc (disccentre, discnormal, discradius, disctexture)
   disc {disccentre, discnormal, discradius
      Fit_Texture_to_Cylinder (disctexture, disccentre, disccentre + discnormal,
discradius)}
#end

// -- End File -----------------------------

Post a reply to this message