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Action:
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Creates a continuous spline edge from a list of positions.
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Filename:
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cstr/cstr_scm/edge_scm.cxx
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APIs:
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api_curve_spline
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Syntax:
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(edge:spline position-list
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[[start-angle | start-direction | spline-condition]
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[end-angle | end-direction]] ["periodic"]
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["exact"])
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Arg Types:
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position-list
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position | (position ... )
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start-angle
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real
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start-direction
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gvector
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spline-condition
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boolean
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end-angle
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real
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end-direction
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gvector
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"periodic"
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string
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"exact"
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string
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Returns:
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spline-edge
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Description:
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The argument
position-list is a list of locations through which the spline should pass. The number of positions in the
position-list
must be at least two. The optional argument
start-direction is the gvector of the tangent to the spline at the start position. The optional argument
end-direction is the gvector of the tangent to the spline at the end position. If either
start-direction or
end-direction is not specified, a free end condition is used at that end. A "free" or "natural" spline condition means that the second derivative at that end is 0.
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To force a "free" end condition, either assign
#f to the argument
spline-condition, or do not specify an argument for the end condition. Specifying
#f results in a "free" end condition at the start, so the tangent direction needs to be specified at the end.
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Specifying an
end-direction vector indicates the end direction of the curve tangent at the end.
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Specify the
start-angle and
end-angle in degrees. If an angle is specified, the curve is tangent to a vector in the
xy plane of the active WCS. The angle specifies the angle between the tangent vector and the
x-axis of the active WCS measured counterclockwise.
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When
"periodic" is included, the interpolation produces a periodic spline, as long as the first and last position in the list are within resabs, and no end conditions are specified. This check is performed lower down the stack.
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If the string
"exact" is included, the interpolation is as accurate as possible. Otherwise, it will be within resfit of the points being interpolated.
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position-list is a list of locations through which the spline should pass.
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start-direction is the gvector of the tangent to the spline at the start position.
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start-angle and
end-angle in degrees specifies the angle between the tangent vector and the
x-axis of the active WCS measured counterclockwise.
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spline-condition forces a "free" end condition by assigning
#f to the argument
spline-condition.
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end-direction vector indicates the end direction of the curve tangent at the end.
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"periodic" is included, the interpolation produces a periodic spline, as long as the first and last position in the list are within resabs, and no end conditions are specified. This check is performed lower down the stack.
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"exact" is included, the interpolation is as accurate as possible. Otherwise, it will be within resfit of the points being interpolated.
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Example:
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; edge:spline
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; Set the view's eye position, target position,
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; and up vector.
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(define viewset (view:set (position 0 0 100)
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(position 0 0 0)
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(gvector 0 1 0)))
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;; viewset
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; Define a new WCS.
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(define wcs (wcs (position 0 0 0) (position 5 0 0)
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(position 0 5 0)))
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;; wcs
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; Create 3 spline edges.
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(define spline1 (edge:spline (list (position 0 0 0)
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(position 5 5 0) (position 10 15 0)
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(position 15 20 0) (position 20 15 0)
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(position 25 5 0) (position 30 0 0))))
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;; spline1
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; spline 1 is shown in green.
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(define spline2 (edge:spline (list (position 0 0 0)
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(position 5 5 0) (position 10 15 0)
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(position 15 20 0) (position 20 15 0)
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(position 25 5 0) (position 30 0 0)) 0 45))
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;; spline2
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; spline 2 is shown in blue.
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(define spline3 (edge:spline (list (position 0 0 0)
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(position 5 5 0) (position 10 15 0)
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(position 15 20 0) (position 20 15 0)
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(position 25 5 0) (position 30 0 0))
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(gvector 0 1 0) (gvector 0 1 0)))
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;; spline3
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; spline 3 is shown in magenta.
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; OUTPUT Example
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Figure 2-19. edge:spline
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