Trefoil

Objects: "torus".
Methods: "#declare", "union{...}", "object{...}", "intersection{...}".

The construction in details:
How to define the radius Ri of the inner circles: The radius of all torus tubes is called by R0.
Ri is the radius of the inner circles.
Ra is the radius of the outer circle.

See the opposite image:
Ri (dark green) = Ra/2 + R0/2.
This increasing by "+ R0/2" is neccesary to get the inner rings ending exactly above <0,0,0> (marked by the red arrow!). Only in this way the rotated plane (or an according box) can cut off the upper parts at the right and left side from the torus. The opposite image shows the right plane of these two planes used for cuting off (transparent yellow).

The inner torus (orange) and
one of the planes used for cuting off (yellow).

// Äußerer Radius:
#declare Ra = 3.00 -R0;
// Radius der inneren Kreise;
#declare Ri  = Ra /2+ R0/2;

#declare Part =
intersection{
torus{ Ri,  R0
       rotate<90,0,0>
       translate<0,-Ra+Ri,0>}
plane { <0,1,0>,0 rotate<0,0, 30>}
plane { <0,1,0>,0 rotate<0,0,-30>}
box{<-Ri-R0,-Ra-R0,-R0>,
     <Ri+R0, 0,R0>}
}// ------- Ende von "Part" ------
union{   //-----------------------
torus{ Ra,  R0
       rotate<90,0,0>
      } // Ende des Torus  -------

object{ Part rotate<0,0,0*120>}
object{ Part rotate<0,0,1*120>}
object{ Part rotate<0,0,2*120>}
}// Ende der Union
//---------------------------- end

Scene description
for POV-Ray:
".txt" file or ".pov" file

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Descriptions and Examples for the POV-Ray Raytracer by Friedrich A. Lohmüller POV-Ray Examples - How To Make Objects for POV-Ray

Trefoil

Objects: "torus". Methods: "#declare", "union{...}", "object{...}", "intersection{...}".

The inner torus (orange) and one of the planes used for cuting off (yellow).

Scene description for POV-Ray: ".txt" file or ".pov" file

Descriptions and Examples for the POV-Ray Raytracer by Friedrich A. Lohmüller

POV-Ray Examples - How To Make Objects for POV-Ray

Objects: "torus".
Methods: "#declare", "union{...}", "object{...}", "intersection{...}".

The inner torus (orange) and
one of the planes used for cuting off (yellow).

Scene description
for POV-Ray:
".txt" file or ".pov" file