graPHIGS Programming Interface: Subroutine Reference

The graPHIGS Programming Interface : Subroutine Reference

GPPSC - Parametric Surface Characteristics

GPPSC (type, data)

Purpose

Use GPPSC to insert a Parametric Surface Characteristics structure element into the open structure following the element pointer or to replace the element pointed at by the element pointer with a Parametric Surface Characteristics structure element depending upon the current edit mode.

During structure traversal, the graPHIGS API uses the type and data parameters to update the Parametric Surface Characteristic entry in the graPHIGS API traversal state list. The graPHIGS API uses this new state to render all subsequent parametric surface primitives until this traversal state list entry is changed.

The Parametric Surface Characteristic traversal state defines the type of line geometry that is generated in the interior of a parametric surface. When rendering a line geometry, all polyline attributes are applied to the line representation.

When rendering a parametric surface, edges (which are controlled by edge attributes), have priority over line geometries, which have priority over rendering surface interiors (which are controlled by interior attributes).

The traversal default for parametric surface characteristics is 1=NONE If a workstation encounters an unsupported type, the parametric surface defaults to 1=NONE

GPPSC is identified as GSE 1008.

Note:

Not all GSEs are supported on all workstations. Use the Inquire List of Generalized Structure Elements (GPQGSE) subroutine determine the GSEs which are supported by an open workstation. See also the workstation descriptors in The graPHIGS Programming Interface: Technical Reference

Parameters

type -- specified by user, fullword integer

Rendering style that is to be applied to the interior of parametric surfaces (1=NONE, 2=ISOPARAMETRIC_LINES )

data -- specified by user, array of integers

Rendering style type dependent data. The required data for each type is listed below. The parameters must be specified in the order shown.

If type=1 ( NONE )

The data parameter is ignored.

If type=2 ( ISOPARAMETRIC_LINES )

The data parameter requires the following format:

 
      ---------------------
      |     Scope of      |
    0 |   Isoparametric   | Fullword integer
      |      Numbers      |
      |-------------------|
      |    Number of      |
    4 |   Isoparametrics  |
      |    in the U       | Fullword integer >=0
      |    direction      |
      |-------------------|
      |    Number of      |
    8 |   Isoparametrics  |
      |    in the V       | Fullword integer >=0
      |    direction      |
      ---------------------

Scope of Isoparametric Numbers

This field defines whether the number of Isoparametrics is to be applied to the surface as a whole or just between knots (1=Surface, 2=Between Knots ) If the surface is uniform and 2=Between Knots is specified, 1=Surface is used instead.

Number of Isoparametrics in the U Direction

These curves are drawn parallel to the v-axis of parameter space. For scope of 1=Surface , this field defines the number of isoparametric curves that are drawn between minimum and maximum parameter limits of the surface. For an untrimmed surface, a value of one would result in an isoparametric curve that is drawn at (vmin+vmax)/2. For a scope of 2=Between Knots , this field defines the number of isoparametric curves that are to be drawn between knots in addition to isoparametric curves through the knot lines. A value of zero would result in an isoparametric curve being drawn at each knot line within the parameter limits of the surface. A value of one would add a curve placed midway between each pair of knots.

Number of Isoparametrics in the V Direction

This parameter is identical to the previous parameter except the isoparametric curves are drawn parallel to the u-axis.

Note: The graPHIGS API only displays isoparametric curves in the active region of a trimmed surface. This means that the trimming curves clip the isoparametric curves.

Error Codes

5: FUNCTION REQUIRES STATE STOP OR NROP (NOT STCL)
102: PARAMETRIC SURFACE CHARACTERISTICS TYPE IS INVALID
103: PARAMETRIC SURFACE CHARACTERISTICS DATA IS INVALID

Related Subroutines

GPNBC2: Non-Uniform B-Spline Curve 2
GPNBC3: Non-Uniform B-Spline Curve 3
GPNBS: Non-Uniform B-Spline Surface
GPSPH: Polysphere
GPTNBS: Trimmed Non-Uniform B-Spline Surface

RCP code

201328907 (X'0C00090B')