The control net.

Overall tolerance for the internal brep representation of this surface. Defaults to nil. Note that a value of nil indicates for SMLib a value of 1.0e-05 of the longest diagonal length of the brep.

Specify this if you want this surface to be a clone of an existing surface (note - this uses a shared underlying surface 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 to attempt automatic endcaps on conversion of this surface to a brep. Note that this might change in future to a keyword value for :min, :max, or :both to provide more control.

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).

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).

Returns non-nil iff this surface is rational, i.e. all weights are not 1.

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

Indicates whether brep representation should undergo a sew-and-orient operation. Defaults to nil.

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.

This controls tessellation for the brep of this surface. The keys are as follows:

• :min-number-of-segments
• :max-3d-edge-factor
• :min-parametric-ratio
• :max-chord-height
• :max-angle-degrees
• :min-3d-edge
• :min-edge-ratio-uv
• :max-aspect-ratio

   (list 
       :min-number-of-segments *tess-min-number-of-segments*
       :max-3d-edge-factor *tess-max-3d-edge-factor*
       :min-parametric-ratio *tess-min-parametric-ratio*
       :max-chord-height *tess-max-chord-height*
       :max-angle-degrees *tess-max-angle-degrees*
       :min-3d-edge *tess-min-3d-edge*
       :min-edge-ratio-uv *tess-min-edge-ratio-uv*
       :max-aspect-ratio *tess-max-aspect-ratio*)

Approximation tolerance for display purposes.

Degree of surface in U direction. Defaults to 3.

Knots in U direction. Default is NIL, which indicates a uniform knot vector in U direction.

Degree of surface in V direction. Defaults to 3.

Knots in V direction. Default is NIL, which indicates a uniform knot vector in V direction.

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

A weight to match each control point. Should be congruent with control-points (i.e. same number of rows and columns). Default is a value of 1.0 for each weight, resulting in a nonrational surface.

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.

The number of isoparametric curves to be displayed in each direction. This value comes from the value of :isos on the display-controls if that exists, and defaults to *isos-default* otherwise.

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).