51. Torso surfaces

A torso surface is a surface formed by a rectilinear generatrix l , which, when it moves in all its positions, is a spatial curve τ, called the cuspidal edge (Fig. 96). The return edge defines the torso completely and is a geometric part of the surface determinant. Algorithmic part is the indication of the tangency of the generators to the return edge.

The conical surface is a special case of the torso, in which the return edge t degenerates to the point S , the vertex of the conical surface. A cylindrical surface is a special case of a torso, in which the return edge is a point at infinity.

A torso surface is a surface formed by a rectilinear generatrix l, which, when it moves in all its positions, is a spatial curve τ, called the cuspidal edge (Fig. 96). The return edge defines the torso completely and is a geometric part of the surface determinant. Algorithmic part is the indication of the tangency of the generators to the return edge.

The conical surface is a special case of the torso, in which the return edge t degenerates to the point S — the apex of the conical surface. A cylindrical surface is a special case of a torso, in which the return edge is a point at infinity.

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