torus

        torus  [surface-desc]  major-radius  minor-radius  cx cy cz  upx upy upz

Create a torus (donut) whose radius is major-radius, centred at (cx cy cz); the thickness of the torus is minor-radius. The orientation of the torus is controlled by (upx upy upz) which defines a vector from the centre of the torus; the major radius is perpendicular to this vector.

In this example a transformed half torus is used to create the curving top-cord of a roof truss. Cylinders are used to create the web members and the bottom-cord. Because the truss object is "named" it will not appear in the scene until it is instantiated, using the syntax:

        object [surface-name] obj-name

        /*
          trusses.ray
          curving roof trusses
          Stephen Peter 24 feb 92
        */
        eyep 14 28 9
        lookp 0 6.8 1
        screen 300 300
        background 1 1 1

        surface red  ambient  .2 0 0  diffuse .4 0 0
        surface blue ambient  0 0 .2  diffuse  0 0 .4

        name truss
            list
                difference      /* remove bottom half of torus */
                    torus 8 .1  0 0 0  0 1 0
                    box -9 -1 -9   9 1 0
                end
                cylinder .1  0 0 0  0 0 8
                cylinder .1  0 0 0  0 0 8   rotate 0 1 0   45
                cylinder .1  0 0 0  0 0 8   rotate 0 1 0  -45
                cylinder .1 -8 0 0  8 0 0
                sphere .1 0 0 0
            end scale 1 1 .5

        object red  truss
        object blue truss translate 0  3 0
        object red  truss translate 0  6 0
        object blue truss translate 0  9 0
        object red  truss translate 0 12 0