Figure 15.11 A playground slide built by extruding a half-circle cross section along a helical spine.
15fig11.wrl	Click on the image to view the VRML scene.

#VRML V2.0 utf8
# The VRML 2.0 Sourcebook
# Copyright (c) 1997
# Andrea L. Ames, David R. Nadeau, and John L. Moreland
Shape {
    appearance Appearance {
        material Material {
            diffuseColor 0.0 1.0 0.7
        }
    }
    geometry Extrusion {
        creaseAngle 1.57
        endCap   FALSE
        beginCap FALSE
        solid    FALSE
        crossSection [
        # Half-circle
            -1.00  0.00,  -0.92 -0.38,
            -0.71 -0.71,  -0.38 -0.92,
             0.00 -1.00,   0.38 -0.92,
             0.71 -0.71,   0.92 -0.38,
             1.00  0.00,
        ]
        spine [
        # Helix
             2.00 0.00 -0.00,   1.85 0.12 -0.77,
             1.41 0.24 -1.41,   0.77 0.36 -1.85,
             0.00 0.48 -2.00,  -0.77 0.61 -1.85,
            -1.41 0.73 -1.41,  -1.85 0.85 -0.77,
            -2.00 0.97  0.00,  -1.85 1.09  0.77,
            -1.41 1.21  1.41,  -0.77 1.33  1.85,
             0.00 1.45  2.00,   0.77 1.58  1.85,
             1.41 1.70  1.41,   1.85 1.82  0.77,
             2.00 1.94  0.00,   1.85 2.06 -0.77,
             1.41 2.18 -1.41,   0.77 2.30 -1.85,
             0.00 2.42 -2.00,  -0.77 2.55 -1.85,
            -1.41 2.67 -1.41,  -1.85 2.79 -0.77,
            -2.00 2.91  0.00,  -1.85 3.03  0.77,
            -1.41 3.15  1.41,  -0.77 3.27  1.85,
             0.00 3.39  2.00,   0.77 3.52  1.85,
             1.41 3.64  1.41,   1.85 3.76  0.77,
             2.00 3.88  0.00,
        ]
    }
}