vprotate(3)

NAME

vpRotate - multiply the current transformation matrix by a rotation matrix

SYNOPSIS

#include <volpack.h>
vpResult
vpRotate(vpc, axis, degrees)
    vpContext *vpc;
    int axis;
    double degrees;

ARGUMENTS

vpc VolPack context from vpCreateContext.

axis Rotation axis code (VP_X_AXIS, VP_Y_AXIS or VP_Z_AXIS).

degrees

Number of degrees to rotate.

DESCRIPTION

vpRotate is used to multiply the current transformation matrix by a 4-by-4 rotation matrix. The rotation axis must be one of the three principal viewing axes and is specified with one of the following codes: VP_X_AXIS X axis
VP_Y_AXIS Y axis
VP_Z_AXIS Z axis The rotation angle is specified in degrees. A positive angle indicates a clockwise rotation when looking towards the positive direction along the axis. For an X-axis rotation, the rotation matrix is: 1 0 0 0

0 cos(d) sin(d) 0
0 -sin(d) cos(d) 0
0 0 0 1 where d stands for the degrees argument.

For a Y-axis rotation, the rotation matrix is:

cos(d) 0 -sin(d) 0

0 1 0 0

sin(d) 0 cos(d) 0

0 0 0 1 For a Z-axis rotation, the rotation

matrix is: cos(d) sin(d) 0 0

-sin(d) cos(d) 0 0

0 0 1 0
0 0 0 1

Use vpCurrentMatrix to set the current transformation matrix. By default, the rotation matrix is post-multiplied (M = M*R where M is the current matrix and R is the rotation matrix). The VP_CONCAT_MODE option to vpSeti can be used to select pre-multiplication.

STATE VARIABLES

The current matrix concatenation parameters can be retrieved with the following state variable codes (see vpGeti(3)): VP_CURRENT_MATRIX, VP_CONCAT_MODE.

ERRORS

The normal return value is VP_OK. The following error return value is possible:

VPERROR_BAD_OPTION

The axis argument is invalid.

SEE ALSO

VolPack(3), vpCreateContext(3), vpCurrentMatrix(3)

VolPack vpRotate(3)