File:Tackle principle.png

 /*
  ================================================
  Demonstrating the principle of the basic tackle
  ------------------------------------------------
  Created by Søren Peo Pedersen - see my user page
  et http://da.wikipedia.org/wiki/Bruger:Peo
  ================================================
  */
 
  #macro WoodTxt(WhiteOut)  // Wood texture with specified
    pigment {               // degree of "whiting out"
      wood
      color_map {
        [0 color rgbt <.9+.1*WhiteOut,.7+.3*WhiteOut,.5+.5*WhiteOut>]
        [1 color rgbt <.7+.3*WhiteOut,.5+.5*WhiteOut,.4+.6*WhiteOut>]
        }
      scale .1
      turbulence .05
      translate <2,0,-1>
      }
    finish {ambient .4+.3*WhiteOut}  
  #end
 
  #macro RopeTxt(WhiteOut)  // Texture for ropes, with specified "whiting out"
    pigment {color rgb <1+.0*WhiteOut,.9+.1*WhiteOut,.6+.4*WhiteOut>}
    finish {ambient .4+.3*WhiteOut}
  #end
 
  #macro Tackle(WhiteOut)   // Renders the tackle, weight and parts of the rope
    #local WheelSideCut=difference {
      cone {<0,0,.03>,.35,<0,0,.13>,.45}
      cone {<0,0,.3>,0,<0,0,-.3>,.6}
      }
 
    #local MetalTxt=texture {   // Metal texture for hooks and weight
      pigment {color rgb .5+WhiteOut/4}
      finish {
        ambient .4+.2*WhiteOut
        reflection rgb .3
        metallic
        }
      }
 
    merge {
      difference {
        box {<-.45,-1,-.3>,<.45,.5,.3>} // "body" of tackle
        box {<-1,-.5,-.1>,<1,1,.1>}     // The "gap" for the wheel
        plane {<3,-1,0>,-.3}            // Left "slanted" side
        plane {<-3,-1,0>,-.3}           // Right "slanted" side
        texture {WoodTxt(WhiteOut) rotate <90,0,0>}
        }
 
      difference {                        // Wheel in the tackle
        cylinder {<0,0,-.09>,<0,0,.09>,.5}  // "Body" of the wheel
        torus {.5,.07 rotate <90,0,0>}      // Groove for the rope
        #object {WheelSideCut}                // Cut-aways on both
        #object {WheelSideCut scale <1,1,-1>} // sides of the wheel
        texture {MetalTxt}
        translate <0,.25,0>
        }
 
      cylinder {<0,.25,-.4>,<0,.25,.4>,.1 // Axle through
        texture {MetalTxt}                // wheel and tackle
        }
 
      sphere_sweep {b_spline,7            // Hook on the tackle
        <  0,-0.7,0>,.1
        <  0,-1  ,0>,.1
        <  0,-1.2,0>,.1
        < .3,-1.5,0>,.09      
        <  0,-1.8,0>,.08      
        <-.3,-1.5,0>,.06
        <-.3,-1.2,0>,.04
        texture {MetalTxt}
        }
 
      merge {                             // Weight attached to the hook
        difference {    // Round part of attachment ring
          torus {.2,.1 rotate <0,0,90>}
          plane {<0,1,0>,0}
          translate <0,-1.75,0>
          }
        cylinder {<0,-1.75,-.2>,<0,-1.85,-.2>,.1} // Straight parts of
        cylinder {<0,-1.75, .2>,<0,-1.85, .2>,.1} // attachment ring
        cone {<0,-1.85,0>,.4,<0,-2.8,0>,.6} // "Body" of the waight
        texture {MetalTxt}
        }
 
      merge {     // Rope around the wheel in the tacle
        difference {
          torus {.5,.07 rotate <90,0,0>}
          plane {<0,-1,0>,0}
          }
        cylinder {<.5,0,0>, // Straight part of rope on right side of wheel
          <.5,#if (WhiteOut=0) 1 #else 6 #end,0>,.07
          }
        translate <0,.25,0>
        texture {RopeTxt(WhiteOut)}
        }
 
      cylinder {    // Free end of rope on left side of the wheel
        <-.5,.25,0>,<-.5,#if (WhiteOut=0) 7 #else 1 #end,0>,.07
        texture {RopeTxt(WhiteOut)}
        }
 
      union {   // Free end of the rope with the hook with ring attached:
        merge {   // Knot and loop at the free end of the rope:   
          #local Count=0;   // The knot
          #while (Count<5)
            torus {.1,.07 translate <-.5,1.45-.14*Count,0>}
            #local Count=Count+1;
          #end
 
          difference {    // Part of rope loop bent around the hook
            torus {.15,.07}
            box {<-1,-1,0>,<0,1,1> rotate <0,-30,0>}
            box {-1,<0,1,0> rotate <0,30,0>}
            rotate <0,0,90>
            translate <-.5,1.8,0>
            }
 
          cylinder {  // Straight part of rope loop, away from viewer
            <0,0,.15>,<0,-.4,.15>,.07
            rotate <30,0,0> translate <-.5,1.8,0>
            }
          cylinder {  // Straight part of rope loop, towards viewer
            <0,0,-.15>,<0,-.4,-.15>,.07
            rotate <-30,0,0> translate <-.5,1.8,0>
            }
 
          texture {RopeTxt(WhiteOut)}
          }
 
        merge { // Hook with ring at the free end of the rope
          sphere_sweep {b_spline,7  // The hook itself
            <-.5,2.8,0>,.1
            <-.5,2.5,0>,.1
            <-.5,2.3,0>,.1
            <-.2,2  ,0>,.09      
            <-.5,1.7,0>,.08      
            <-.8,2  ,0>,.06
            <-.8,2.3,0>,.04
            }
          torus {.2,.1 rotate <90,0,0> translate <-.5,2.72,0>}  // The ring on the hook
          texture {MetalTxt}
          }
 
        #if (WhiteOut=0)    // Using WhiteOut property to specify the length of the
          translate <0,6,0> // free end of the rope, and hence the knot and hook
        #end
        }
      }
  #end
 
  #macro LengthArrow (Length,NameSymbol)  // Double arrow with symbol for indicating lengths
    #local ArrowHead=difference {
      box {<-1,-1,-.001>,<0,0,.001> rotate <0,0,45> scale <1,3,1>}
      plane {<0,1,0>,-.5}
      }
    merge {
      box {<-.5,-.01,-.001>,<.5,.01,.001>}
      #object {ArrowHead scale <1,-1,1> translate <0,.01,0>}
      box {<-.01,.51,-.01>,<.01,Length-.51,.001>}
      #object {ArrowHead translate <0,Length-.01,0>}
      box {<-.5,Length-.01,-.001>,<.5,Length+.01,.001>}
      #object {NameSymbol
        translate <0,
          Length/2+(min_extent(NameSymbol).y-max_extent(NameSymbol).y)/2
          ,0>
        }
      pigment {color rgb 0}
      no_shadow
      no_reflection
      }
  #end
 
  #macro ForceArrow (Length,NameSymbol)   // Fat arrow with symbol for indicating forces
    merge {
      difference {
        box {<-1,-1,-.001>,<0,0,.001> rotate <0,0,45> scale <1,2,1>}
        plane {<0,1,0>,-.5}
        translate <0,Length,0>
        }
      box {<-.1,0,-.01>,<.1,Length-.5,.01>}
      #object {NameSymbol
        translate <0,
          Length/2+(min_extent(NameSymbol).y-max_extent(NameSymbol).y)/2
          ,0>
        }
      pigment {color rgb 0}
      no_shadow
      no_reflection
      }
  #end
 
  // The scenario:
  box {<.3,2,-1000>,<.7,3,1000> texture {WoodTxt(0)}}   // Wooden beam
 
  merge { // End of rope tied around the wooden beam:
    cylinder {<.77,3,0>,<.77,2,0>,.07}  // Down the far side of the beam
    intersection {  // Around farthest, upper corner on beam
      torus {.07,.07}
      box {<0,-1,-1>,<1,1,0>}
      rotate <90,0,0>
      translate <.7,3,0>
      }
    cylinder {<.3,3.07,0>,<.7,3.07,0>,.07}  // Horizontal part above beam
    intersection {  // Around the nearest, upper corner on beam
      torus {.07,.07}
      box {-1,<0,1,0>}
      rotate <90,0,0>
      translate <.3,3,0>
      }
    cylinder {<.23,3,0>,<.23,2,0>,.07}  // Down the near side of the beam
    difference {    // Around the nearest, lower corner on beam
      torus {.07,.07}
      plane {<0,0,1>,0}
      plane {<0,0,-1>,0 rotate <0,25,0>}
      rotate <90,0,0>
      translate <.3,2,0>
      }
    cylinder {<-.07,0,0>,<-.07,-.7,0>,.07 // From nearest lower corner on
      rotate <0,0,25> translate <.3,2,0>  // the beam down to the knot
      }
    cylinder {<.07,0,0>,<.07,-.7,0>,.07   // From farthest lower corner on
      rotate <0,0,-25> translate <.7,2,0> // the beam down to the knot
      }
 
    #local Count=0; // The knot just underneath the wooden beam
    #while (Count<5)
      torus {.1,.07 translate <.5,1.45-.14*Count,0>}
      #local Count=Count+1;
    #end
 
    texture {RopeTxt(0)}
    }
 
  #object {Tackle(0)}   // Tackle in upper position, at full "color density"
  #object {Tackle(.7) translate <0,-6,0>} // "Whited-out" tackle at lower position
 
  #object {LengthArrow(6,   // Indicating the length "s" the weight travels
    text {ttf "cmmi10.ttf"
      "s",.001,0 translate <.1,0,0>}
    ) translate <1.2,-8.3,0>}
 
  #object {LengthArrow(12,  // Indicating the length "2s" the hook travels
    union {
      text {ttf "cmr10.ttf"
        "2",.001,0 translate <-.95,0,0>}
      text {ttf "cmmi10.ttf"
        "s",.001,0 translate <-.45,0,0>}
        }
  ) translate <-1.4,-3.28,0>}
 
  #object {ForceArrow(4,    // Indicating the lifting force "F" on the weight
    text {ttf "cmmi10.ttf"
      "F",.001,0 translate <-.85,0,0>}
      )
    translate <-1,-8.8,0>
    }
 
  #object {ForceArrow(2,    // Indicating the force "F/2" excerted on the rope end
    union {
      text {ttf "cmmi10.ttf"
        "F",.001,0 translate <.3,.9,0>}
      box {<.2,.70,0>,<1.1,.74,.001>}
      text {ttf "cmr10.ttf"
        "2",.001,0 translate <.4,-.1,0>}
      }
      )
    translate <.3,7,0>
    }
 
  //  background {color rgb 1}  // Provides the white backdrop
 
  camera {              // Camera: Indicates where the scenario is
    up <0,1,0>          // seen from, and where the viewer "looks"
    right <.25,0,0>
    location <-5,5,-30>
    look_at <-.3,.37,0>
    angle 8.4
    }
 
  light_source {<-1000,2500,-2000> color rgb 1} // Illumination