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)