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general syntax:
object{ Segment_of_CylinderRing(
R_out,
R_in,
Height_in_Y,
Segment_Angle
) //---------------
texture{ ... ... }
scale <1,1,1>
rotate<0,0,0>
translate<0,0,0>
} // end of object --------- |
R_out = the outer radius of the cylindrical ring,
R_in = the inner radius of the cylindrical ring,
Height = the height of the ring segment,
Segment_Angle = the angle in degrees lefthanded orientated!
For Segment_Angle = 0 we get a closed ring or a tube.
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Examples:
#include "shapes3.inc"
// -------------------------------------------------
object{ Segment_of_CylinderRing( 3.75,2.25,0.2,-300)
texture{ Chrome_Metal
finish { phong 1}
} // end of texture
} // -----------------------------------------
object{ Segment_of_CylinderRing( 1.75,1.5,2.0,-270)
texture{ pigment {color White*1.1}
finish { phong 1 }
} // end of texture
} // -----------------------------------------
object{ Segment_of_CylinderRing( 2.5, 3.0, 1.0, -80)
texture{ pigment{ color rgb< 0.7, 1, 0.0> }
finish { phong 1 reflection 0.2}
} // end of texture
} // -----------------------------------------
object{ Segment_of_CylinderRing( 1.1, 0.8, 1.5, 0)
texture{ pigment{ color rgb< 1,0.7, 0.0> }
finish { phong 1 reflection 0.2}
} // end of texture
} // ----------------------------------------- |
Macro in detail:
First we subtract from a cylinder with the radius R_out a smaller cylinder with the radius R_in
by making an intersection of the first cylinder with the inverse of the second cylinder.
Then 2 boxes rotated against another were used to cut out the wanted segment.
For this we have to consider two cases:
1. abs(Segment_Angle) <= 180 degrees (just an intersection of the torus and the two boxes) and
2. abs(Segment_Angle) > 180 degrees (an intersection of the torus and the union of the two boxes):
The following images show how this macro works
(the boxes are visualizised in texture glass):
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abs(Segment_Angle) <= 180 degrees
R_out = 1.25, R_in = 0.75, Angle =-145 |
abs(Segment_Angle) > 180 degrees
R_out = 1.25, R_in = 0.75, Angle =-215 |
//--------------------------- Segment_of_CylinderRing()
#macro Segment_of_CylinderRing( R_out, R_in,
Height,
Segment_Angle
) //------------
#local D = 0.0001; // just a little bit
#if (Height = 0 ) #local Height = D; #end
#if (Height < 0 ) #local D = -D; #end
#if (R_out < R_in)
#local X=R_out; #local R_out=R_in; #local R_in=X;
#end
#if (Segment_Angle < 0)
#local Negativ_Flag = 1;
#local Segment_Angle = -Segment_Angle;
#else
#local Negativ_Flag = 0;
#end
#if (Segment_Angle >= 360)
#local Segment_Angle = mod (Segment_Angle, 360);
#end
intersection{
cylinder { <0,0,0>,<0,Height,0>, R_out
} // end of outer cylinder ----------
cylinder { <0,-D,0>,<0,Height+D,0>, R_in
inverse
} // end of inner cylinder ----------
#if (Segment_Angle > 0) // -----------------------
#if (Segment_Angle >= 180)
union{
#end // then use union!
box { <-R_out+D,-D,0>,< R_out+D, Height+D, R_out+D>
}// end of box
box { <-R_out+D,-D,-R_out+D>,< R_out+D, Height+D,0>
rotate<0,-Segment_Angle,0>
}// end of box
#if (Segment_Angle >= 180)
} // end of union
#end // end of union, if union is used!
#if (Negativ_Flag = 0) rotate<0,-Segment_Angle,0>
scale<-1,1,-1>
#end // of "#if (Negativ_Flag = 0)" ------------
#end // of "#if (Segment_Angle > 0)" ------------
} // end of intersection
#end // --------- end of macro Segment_of_CylinderRing() |
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