CenterStage Object Class: CurveFromSurface Subclass of: Curve Requires reference to a Surface object The CurveFromSurface class lets you create a Curve object that relates to a Surface object. You specify a parametric curve in the domain of the surface, and that curve is computed in space. Then the second part of the curve function is computed, and its result is added to the value of the point on the surface, either in absolute coordinates, or in relation to a frame on the surface. The frame is determined by the normal vector to the surface and the partial derivatives of the surface with respect to its parameters (note that this need not be an orthonormal basis). In addition to the standard Curve directives, CurveFromSurface supports the following: Function param curve func [-frame | -absolute] Here the "param" and "func" arguments are the same as for the standard Curve. The -frame and -absolute options determine whether the result of the function is in the coordinate system of the surface frame or in absolute coordinates (the default). If -frame is provided, then the surface and curve must be in 3-space, and the frame is computed numerically. The x-coordinate of the result corresponds to the normal direction for the surface, the y-coordinate to the direction of the first partial derivative of the surface, and the z-coordinate to the direction of the second partial derivative. The "curve" argument is a script that gives a curve within the surface's domain parametrically. For example: Function {t} { let (x,y) = (t,t^2) } { let (x,y,z) = (.1,0,0) } -frame produces a curve that is offset from the surface by .1 in the normal direction along the curve that is the image of a parabola in the domain of the surface.