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*GL3.2 for AIX: Graphics Library (GL) Technical Reference*

## rcrvn Subroutine

### Purpose

Draws a series of rational curve segments.

### Libraries

Graphics Library

C (**libgl.a**)

FORTRAN (**libfgl.a**)

### C Syntax

**void rcrvn(Int32 ***n***, Coord ***geom*** [ ][4]) **

### FORTRAN Syntax

**SUBROUTINE RCRVN(***n***,*** geom***)**
**INTEGER*4 ***n*
**REAL ***geom***(4,***n***)**

### Description

The **rcrvn** subroutine draws a series of rational
cubic spline curve segments using the current basis and precision.

The control points specified in the *geom* parameter determine the shapes of the curve segments and are used four at a time. The *n* parameter specifies the number of
control points to be used in drawing the curve. For example, if *n *is 6, three curve segments are drawn:

- Using points 0,1,2,3 as control points.
- Using points 1,2,3,4 as control points.
- Using points 2,3,4,5 as control points.

If the current basis is a
B-spline,
Cardinal spline, or
basis with similar properties, the curve segments are joined end to end and appear as a single curve.

### Parameters

*n* |
Specifies the number of control points to be used in drawing the curve. |

*geom* |
Specifies the matrix containing the control points of the curve segments. |

### Implementation Specifics

This subroutine is part of GL in the AIXwindows Environment/6000 Version 1, Release 2 with AIXwindows/3D Feature.

### Files

**/usr/include/gl/gl.h** |
Contains C language constant and variable type definitions for GL. |

**/usr/include/gl/fgl.h** |
Contains FORTRAN constant and variable type definitions for GL. |

### Related Information

Drawing a cubic spline curve with the **crv** subroutine.

Drawing a series of curve segments with the **crvn** subroutine.

Setting the current cubic spline curve basis matrix with the **curvebasis** subroutine.

Setting the number of line segments that compose a cubic spline curve with the **curveprecision** subroutine.

Defining a cubic spline basis matrix with the **defbasis** subroutine.

Drawing a rational curve with the **rcrv** subroutine.

AIX Graphics Library Overview, Drawing NURBS Curves and Surfaces, and Drawing Wire Frame Curves and Surface Patches.

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