24 lines (15 with data), 362 Bytes

//this fiel will draw a cylinder along the main axis of the joint

ref1={

  

   AnyRefNode XCyl={  
    sRel={-cyl.Length*0.5,0,0};
    ARel=RotMat(pi*0.5,y);

    AnySurfCylinder cyl={
      Radius=0.001;
      Length=0.02;
      AnyDrawParamSurf surf={
      Opacity = 0.1;
      RGB={0,0.2,1};
      };
    };
   };
   
  
}; //ref1