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)