Name

glMultMatrix — multiply the current matrix with the specified matrix

C Specification

void glMultMatrixf(const GLfloat * m);
 
void glMultMatrixx(const GLfixed * m);
 

Parameters

m

Points to 16 consecutive values that are used as the elements of a 4x4 column-major matrix.

Description

glMultMatrix multiplies the current matrix with the one specified using m, and replaces the current matrix with the product.

The current matrix is determined by the current matrix mode (see glMatrixMode). It is either the projection matrix, modelview matrix, or the texture matrix.

Examples

If the current matrix is C, and the coordinates to be transformed are, v= v[0] v[1] v[2] v[3] , then the current transformation is Cxv , or

( c[0] c[4] c[8] c[12] c[1] c[5] c[9] c[13] c[2] c[6] c[10] c[14] c[3] c[7] c[11] c[15] ) x ( v[0] v[1] v[2] v[3] )

Calling glMultMatrix with an argument of m= m[0], m[1], ... m[15] replaces the current transformation with CxM xv , or

( c[0] c[4] c[8] c[12] c[1] c[5] c[9] c[13] c[2] c[6] c[10] c[14] c[3] c[7] c[11] c[15] ) x ( m[0] m[4] m[8] m[12] m[1] m[5] m[9] m[13] m[2] m[6] m[10] m[14] m[3] m[7] m[11] m[15] ) x ( v[0] v[1] v[2] v[3] )

Where ``x'' denotes matrix multiplication, and v is represented as a 4x1 matrix.

Notes

While the elements of the matrix may be specified with fixed point or single precision, the GL may store or operate on these values in less than single precision.

In many computer languages 4x4 arrays are represented in row-major order. The transformations just described represent these matrices in column-major order. The order of the multiplication is important. For example, if the current transformation is a rotation, and glMultMatrix is called with a translation matrix, the translation is done directly on the coordinates to be transformed, while the rotation is done on the results of that translation.

Associated Gets

glGet with argument GL_MATRIX_MODE

glGet with argument GL_MODELVIEW_MATRIX

glGet with argument GL_PROJECTION_MATRIX

glGet with argument GL_TEXTURE_MATRIX

See Also

glLoadIdentity, glLoadMatrix, glMatrixMode, glPushMatrix

Copyright

Copyright © 2003-2004 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.