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Action:
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Evaluates a position on a parametric surface.
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Filename:
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kern/kern_scm/surf_scm.cxx
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Syntax:
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(surface:eval srf su sv [level])
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Arg Types:
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srf
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surface
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su
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real
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sv
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real
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level
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integer
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Returns:
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real ...
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Description:
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This extension finds the position on a parametric surface with the given parameter values and optionally calculates the first and second derivatives.
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srf specifies the surface to evaluate.
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su specifies the
u parameter value.
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sv specifies the
v parameter value.
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level specifies the depth of evaluation, and it has the following valid values:
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0
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= turns the position
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1
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= Returns the position and the first derivative (xu,
xv)
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2
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= Returns the position, and the first and second derivatives (xuu,
xuv,
xvv)
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Example:
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; surface:eval
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; Create a planar face.
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(define face1
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(face:plane (position 0 0 0) 30 40))
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;; face1
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; Evaluate the position of a point
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; on the planar surface.
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(surface:eval (surface:from-face face1) 15 15 0)
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;; (#[position 15 15 0])
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; Create a conical surface.
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(define cone1
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(face:cone (position 0 0 0) (position 0 50 0)
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30 20 0 180))
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;; cone1
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; Evaluate the position and the first derivative
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; of a point on the conical surface.
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(surface:eval (surface:from-face cone1) 0.5 0.5 1)
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;; (#[position 23.7458553521721 14.7087101353638
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;; -12.9724199023621] #[gvector -5.16324300907818
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;; 29.4174202707276 2.82069251152796]
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;; #[gvector -12.9724199023621 0
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;; -23.7458553521721])
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