Référence : Povray Internal Functions



With some sets of parameters, it looks like a torus with a helical winding around it. The winding optionally has grooves around the outside.

• P0 : Major radius.
• P1 : Number of winding loops.
• P2 : Twistiness of winding. When zero, each winding loop is separate. When set to one, each loop twists into the next one. When set to two, each loop twists into the one after next.
• P3 : Fatness of winding ?
• P4 : Threshold. Setting this parameter to 1 and the threshold to zero has s similar effect as setting this parameter to zero and the threshold to 1.
• P5 : Negative minor radius? Reducing this parameter increases the minor radius of the central torus. Increasing it can make the torus disappear and be replaced by a vertical column. The value at which the surface switches from one form to the other depends on several other parameters.
• P6 : Another fatness of winding control ?
• P7 : Groove period. Increase this for more grooves.
• P8 : Groove amplitude. Increase this for deeper grooves.
• P9 : Groove phase. Set this to zero for symmetrical grooves.

L'exemple ci-dessous utilise les paramètres trouvés dans la partie "Isosurfaces helix spirals" du site Andrea Lohmüller & Friedrich A. Lohmüller Script :

// --------------------------------------------------------------------------
// --- HDRI SKY SPHERE ------------------------------------------------------
// --------------------------------------------------------------------------
sphere {
  <0,0,0>, 1000
  pigment {
    image_map {
    hdr "galileo_probe.hdr"
    once
    interpolate 2
    map_type 7
    }
  }
  finish {
    ambient 1
    diffuse 0
    }
  hollow
  no_image
  }



// --------------------------------------------------------------------------
// --- HELICAL TORUS ISOSURFACE ---------------------------------------------
// --------------------------------------------------------------------------
isosurface {
  function {
    f_helical_torus (x, y, z, 1, 9, 5, 0.25, 0.10, -0.15, 0, 1, 1,  0)
    }          
  contained_by {
    box { <-1.5,-1.0, -1.5>, <1.5, 1.0, 1.5> }
    }
  threshold 0.001
  accuracy 0.001
  max_gradient 15

  texture { T_Chrome_2C }
  translate< 0, dH, 0>
  rotate -5*z
  }

Il n'y a pas de source de lumière dans cette scéne mais vous remarquerez le paramètre ambient 1 dans la partie 'HDRI SKY SPHERE'. Vous pouvez voir quelques images faites avec cet objet dans la partie Galerie