Specify this if you want this curve to be a clone of an existing curve. (note - this uses a shared underlying curve object, it does not make a copy)

The RGB color of this object as imported from an external format (e.g. IGES) or as specified in :display-controls. Defaults to the foreground color specified in *colors-default*. This message should not normally be overridden in user application code.

Indicates whether the object should effectively be a hidden-object even if specified in :objects. Default is nil.

Synonym for the layer.

Points to a pre-existing image file to be displayed instead of actual geometry for this object. Defaults to nil

The primary IGES-compatible level (layer) on which this object resides. Defaults to the first of the levels. This slot can be overridden in user code to specify a new layer which will be written out when this object is exported with the IGES output-format.

The IGES-compatible levels (layers) on which this object resides. GDL does not currently support writing out multiple levels (layers) through the IGES writer ; only the first of these will be output if the object is exported with the IGES output-format (please contact Genworks if you need all levels (layers) to be written out).

The left front bottom and right rear top corners, in global coordinates, of the rectangular volume bounding this geometric object.

This is synonymous with the orientation.

If non-nil, this function gets invoked when the user clicks the object in graphics front-ends which may or may not support this functionality (see viewport-html-div).

The root-level node in this object's ``tree'' (instance hierarchy).

All objects from the :objects specification, including elements of sequences as flat lists. Any children which throw errors come back as a plist with error information

Determines how the name of objects of this type will be printed in most places. This defaults to the name-for-display (generally the part's name as specified in its parent), followed by an index number if the part is an element of a sequence.

The corresponding UV curve for the primary surface on which this curve lies, if any. If this is not a surface-curve, this will return an error.

Additional objects to display in Tatu tree. Typically this would be a subset of hidden-children. Defaults to NIL.

Approximation tolerance for display purposes. Defaults to the tolerance of the built-from curve, if one exists, otherwise defaults to the *display-tolerance*.

Indicates in global coordinates where the center of the reference box of this object should be located.

May contain keywords and values indicating display characteristics for this object. The following keywords are recognized currently:

:color

color keyword from the *color-table* parameter, or an HTML-style hexidecimal RGB string value, e.g. "#FFFFFF" for pure white. Defaults to :black.

:line-thickness

an integer, defaulting to 1, indicating relative line thickness for wireframe representations of this object.

:dash-pattern

(currently PDF/PNG/JPEG only). This is a list of two or three numbers which indicate the length, in pixels, of the dashes and blank spaces in a dashed line. The optional third number indicates how far into the line or curve to start the dash pattern.

Z-axis dimension of the reference box. Defaults to zero.

Y-axis dimension of the reference box. Defaults to zero.

Indicates the absolute Rotation Matrix used to create the coordinate system of this object. This matrix is given in absolute terms (i.e. with respect to the root's orientation), and is generally created with the alignment function. It should be an orthonormal matrix, meaning each row is a vector with a magnitude of one (1.0).

X-axis dimension of the reference box. Defaults to zero.

The left front bottom and right rear top corners, in global coordinates, of the rectangular volume bounding the tree of geometric objects rooted at this object.

The direction pointing from the start to the end.

The point returned by evaluating the curve function at u2.

The surfaces on which this curve lies.

The point returned by evaluating the curve function at u1.

This will be t if the curve is generated successfully, nil otherwise.

The highest parameter value of the underlying mathematical definition for this parametric curve

The lowest parameter value of the underlying mathematical definition for this parametric curve

Equal to the natural u-min of the curve.

Equal to the natural u-max of the curve.

The first derivative of this curve. The degree will be one less than the degree of this curve.

The second derivative of this curve. The degree will be two less than the degree of this curve.

The given parameter evaluated on the second derivative curve of this curve. Note that this is only valid if this curve has degree of at least two (2), and will throw an error otherwise.

arguments:

parameter Number

The desired parameter to be evaluated on the second derivative curve

Returns four values which are the control points, the weights, the knots, and the degree of the curve.

.

keyword arguments:

3d-tolerance Allowed maximum distance between curve segments, Default Value: *3d-tolerance-default*

angle-tolerance Allowed maximum angle in radians between end/start tangents of curve segments, Default Value: *angle-tolerance-default

minimum-segment-length Allowed minimum curve segment length, Default Value: *minimum-segment-length-default*

continuous:

if ends are within *3d-tolerance-default* and tangents are within *angle-tolerance-default*, :closed if ends are within *3d-tolerance-default* but tangents are not within *angle-tolerance-default*, and :open if ends are not within *3d-tolerance-default*.

The reciprocal of the radius of curvature at the given parameter.

First point of intersection between this curve and the other curve given as the argument. This function also returns a second value, which is a surface point representing the end of a contiguous segment, if any, associated with the surface point given as the primary return value. A NIL value as this second return value indicates that there was no contiguous segment, only an intersecting point as indicated by the surface point given as the primary return value.

arguments:

other-curve GDL Curve

The curve with which to intersect

keyword arguments:

distance-tolerance Number, Default Value: *3d-tolerance-default*

Distance for two points to be considered coincident

note:

use get-parameter-of and get-3d-point-of to extract components of a surface point.

Points of intersection between this curve and another curve. This function also returns a second value, which is a list of surface points representing the ends of contiguous segments, if any, associated with the surface point in the same position in the primary returned list. NIL values in this second returned list indicate that there was no contiguous segment, only an intersecting point as indicated by the surface point in the primary returned list.

arguments:

other-curve GDL Curve

The curve with which to intersect

keyword arguments:

distance-tolerance Number, Default Value: *3d-tolerance-default*

Distance for two points to be considered coincident

note:

use get-parameter-of, get-3d-point-of, and get-uv-point-of to extract components of a surface point.

The returned list of plists contains information about the points where the tangents of this curve and those of the curve given as the argument are equal.

arguments:

curve GDL Curve object

Given a 3D point, returns the point(s) projected normally onto the curve.

keyword arguments:

distance-tolerance Number, Default Value: [covers

The 3D point must be within this distance of the curve for a successful drop

Returns the specified number of parameters equally spaced along the curve.

arguments:

number Number

How many parameters to return

keyword arguments:

spacing Keyword Symbol, :parametric or :arc-length, Default Value: :arc-length

:arc-length is the default

Returns the specified number of points equally spaced along the curve.

arguments:

number Number

How many points to return

keyword arguments:

spacing Keyword Symbol, :parametric or :arc-length, Default Value: :arc-length

Defaults to :arc-length

arc-length-approximation-tolerance Number, Default Value: *zero-epsilon*

A smaller number gives tighter arc length approximation. Scaled to curve exent

Given a point and a vector defining a plane, returns T or NIL depending whether this curve lies in the plane. Also returns a second value which is the maximum distance of the curve from the plane.

arguments:

plane-point 3d-point

Point on the plane

plane-normal 3d-vector

Normal vector of the plane

keyword arguments:

distance-tolerance Number, Default Value: *3d-tolerance-default*

Allowed distance of any point on the curve from the plane

Returns a bbox object, answering xmin, ymin, zmin, xmax, ymax, and zmax, for a box containing the convex hull (i.e. the control points) of this curve and oriented according to the given center and orientation.

The returned plist contains information about the maximum distance from this curve to the curve given as the argument.

arguments:

curve GDL Curve object

The returned plist contains information about the maximum distance from this curve to the point given as the argument.

arguments:

point 3D Point

The returned plist contains information about the minimum distance from this curve to the curve given as the argument.

arguments:

curve GDL Curve object

The returned plist contains information about the minimum distance from this curve to the point given as the argument.

arguments:

point 3D Point

The minimum radius of curvature for the curve. A second value is also returned, which is a surface point indicating the point on the curve where this minimum radius occurs. A third value is also returned, which is a list of additional curve parameters where similar minimum radii occur.

The normal of the curve at the given parameter value, i.e. the vector pointing from the point on the curve at this parameter to the center of the osculating circle at that point. if the curve has no curvature at the given parameter, NIL is returned.

arguments:

parameter Number

The desired parameter to be evaluated on the curve

Returns point at given parameter offset by given distance.

arguments:

curve-parameter Number

The curve parameter to start from

distance Number

The distance to offset

Returns non-NIL if the given parameter lies within the parameter range of this curve.

arguments:

parameter Number

The parameter to be tested

Returns the parameter representing a point offset from the start of the curve by the given length.

arguments:

distance Number

The arc length from the start

Returns the parameter of the given point on the curve.

arguments:

point Point

The point of which the parameter should be calculated

The minimum and maximum parameter values for this parametric curve.

First point of intersection between this curve and the plane denoted by plane-point and plane-normal

note:

use get-parameter-of and get-3d-point-of to extract components of a surface point.

Points of intersection between this curve and the plane denoted by plane-point and plane-normal.

note:

use get-parameter-of and get-3d-point-of to extract components of a surface point.

The point on the curve corresponding to the given parameter value.

arguments:

parameter Number

The desired parameter to be evaluated on the curve

The radius of curvature (i.e. radius of the osculating circle) at the given parameter.

arguments:

parameter Number

The parameter at which to compute radius of curvature

Returns the first point of intersection between this curve and the surface given as an argument.

arguments:

surface GDL Surface object

The surface to intersect with this curve

keyword arguments:

3d-tolerance Number, Default Value: *3d-tolerance-default*

The tolerance to use for intersecting

Returns the point(s) of intersection between this curve and the surface given as an argument.

arguments:

surface GDL Surface object

The surface to intersect with this curve

keyword arguments:

3d-tolerance Number, Default Value: *3d-tolerance-default*

The tolerance to use for intersecting

The curve tangent at the given parameter value. Supplementary values returned are: the 3D point at the parameter value. If keyword argument :include-curvature? is given as non-NIL, the radius of the osculating circle, the center for the osculating circle, the normal for the osculating circle, and the curve normal are also returned. Note: If :include-curvature? is given as non-NIL and the curve has no curvature at the specified parameter, NIL is returned for each of these four values.

arguments:

parameter Number

The desired parameter to be evaluated on the curve

keyword arguments:

include-curvature? Boolean (T or NIL), Default Value: nil

Indicates whether to compute curvature information

The returned list of plists contains information about the points where the tangents of this curve and the vector given as the argument are equal.

arguments:

vector GDL Vector

The total length of the curve from given start-parameter to given end-parameter.

keyword arguments:

u1 Number, Default Value: (the u1)

The start parameter for computing the length

u2 Number, Default Value: (the u2)

The end parameter for computing the length

tolerance Number, Default Value: 0.01

The tolerance (absolute or relative to curve extent) for computing the length

tolerance-type Keyword Symbol, :relative or :absolute, Default Value: :relative

The type of the specified tolerance

Returns a curve which is trimmed from parameter-1 to parameter-2.

arguments:

parameter-1 Number

The start parameter

parameter-2 Number

The end parameter