GLMULTMATRIX() MachTen Programmer’s Manual GLMULTMATRIX()

NAME
glMultMatrixd, glMultMatrixf - multiply the current matrix
with the specified matrix

C SPECIFICATION
void glMultMatrixd( const GLdouble *m )
void glMultMatrixf( const GLfloat *m )

delim $$

PARAMETERS
m Points to 16 consecutive values that are used as the
elements of a $4 times 4$ 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 $C ~times~ v$, or

down 130
{{ left ( matrix {
ccol { c[0] above c[1] above c[2] above c[3] }
ccol { c[4] above c[5] above c[6] above c[7] }
ccol { c[8] above c[9] above c[10] above c[11] }
ccol { c[12]~ above c[13]~ above c[14]~ above c[15]~ }
} right ) } ~~ times ~~ {left ( matrix { ccol { v[0]~
above v[1]~ above v[2]~ above v[3]~ } } right )} }

Calling glMultMatrix with an argument of $"m" = m[0],
m[1], ..., m[15]$ replaces the current transformation with
$(C ~times~ M) ~times~ v$, or

down 130
{{ left ( matrix {
ccol { c[0] above c[1] above c[2] above c[3] }
ccol { c[4] above c[5] above c[6] above c[7] }
ccol { c[8] above c[9] above c[10] above c[11] }
ccol { c[12]~ above c[13]~ above c[14]~ above c[15]~ }
} right ) } ~~ times ~~ { left ( matrix {
ccol { m[0] above m[1] above m[2] above m[3] }
ccol { m[4] above m[5] above m[6] above m[7] }
ccol { m[8] above m[9] above m[10] above m[11] }
ccol { m[12]~ above m[13]~ above m[14]~ above m[15]~ }
} right ) } ~~ times ~~ {left ( matrix { ccol { v[0]~
above v[1]~ above v[2]~ above v[3]~ } } right )} }

Where ’$times$’ denotes matrix multiplication, and $v$ is
represented as a $4 ~times~ 1$ matrix.

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

In many computer languages $4 times 4$ arrays are repre-
sented 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 glMultMa-
trix 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 transla-
tion.

ERRORS
GL_INVALID_OPERATION is generated if glMultMatrix is exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd.

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

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