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

## curvebasis Subroutine

### Purpose

Sets the current cubic spline curve basis matrix.

### Libraries

Graphics Library

C (**libgl.a**)

FORTRAN (**libfgl.a**)

### C Syntax

**void curvebasis(Int32 ***basis_id***)**

### FORTRAN Syntax

**SUBROUTINE CURVEB(***basis_id***)**
**INTEGER*4 ***basis_id*

### Description

The **curvebasis** subroutine sets a basis matrix as defined by the **defbasis** subroutine as the current basis matrix to draw curve segments. The basis matrix determines how the system uses the
control points when drawing a curve.

Depending on the basis matrix, the system draws
Bezier curves,
Cardinal spline curves,
B-spline curves, and others. The system does not restrict you to a limited set of basis matrices. You can define basis matrices to match whatever constraints you want to place on the curve.

### Parameter

*basis_id* |
Specifies the basis identifier of the basis matrix to use when drawing a curve. |

### Example

The example C language program **curve1.c** uses the **curvebasis** subroutine to select each of three previously defined basis matrices, then draws a curve using each basis matrix.

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

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

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

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