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

crvn Subroutine


Draws a series of curve segments.


Graphics Library

C (libgl.a)

FORTRAN (libfgl.a)

C Syntax

void crvn(Int32 n, Coord geom [ ][3])


REAL geom(3, n)


The crvn subroutine draws a series of cubic spline segments using the current basis and precision. The control points determine the shapes of the curve segments and are used sequentially four at a time.

For example, if there are six control points, there are three possible sequential selections of four control points. Thus, crvn draws three curve segments: the first using control points 0,1,2,3; the second using control points 1,2,3,4; and the third using control points 2,3,4,5.

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


geom Specifies a matrix of 3-D points.
n Number of points in the matrix referenced by geom.


The example C language program curve2.c uses the crvn subroutine to draw a curve with six control points.

Implementation Specifics

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


/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.

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.

Drawing a series of rational curve segments with the rcrvn subroutine.

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

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