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Action:
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Evaluates the tangent gvector of an edge or a curve at the specified parameter.
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Filename:
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kern/kern_scm/crv_scm.cxx
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Syntax:
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(curve:eval-tan edge-or-curve parameter)
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Arg Types:
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edge-or-curve
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curve | edge
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parameter
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real
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Returns:
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gvector
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Errors:
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EDGE with no
CURVE
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Description:
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The parameterization of all curves is normalized to lie in the interval 0 to 1, therefore, evaluating at
parameter=0 indicates the start point of the curve.
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edge-or-curve specifies an edge or a curve.
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parameter specifies the position on the curve to evaluate. If the specified parameter lies outside the range 0 to 1, this extension returns an implicit gvector. A spline can only reliably be evaluated for parametric values from 0 to 1; if
parameter is outside of this range for a spline edge, the returned gvector is meaningless.
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Example:
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; curve:eval-tan
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; Create a circular edge.
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(define edge1
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(edge:circular
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(position 0 0 0) 38 0 100))
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;; edge1
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; Evaluate the tangent at a specific parameter.
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(curve:eval-tan edge1 0.23)
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;; #[gvector -0.390731128489274 0.92050485345244 0]
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