- push and pop the current matrix stack



C SPECIFICATION


C SPECIFICATION


DESCRIPTION

       There is a stack of matrices for each of the matrix modes.
       In GL_MODELVIEW mode, the stack depth is at least 32.   In
       the   other   modes,   GL_COLOR,   const(PROJECTION),  and
       GL_TEXTURE, the depth is at least 2.  The  current  matrix
       in any mode is the matrix on the top of the stack for that
       mode.

       glPushMatrix pushes the current matrix stack down by  one,
       duplicating   the   current  matrix.   That  is,  after  a
       glPushMatrix call, the matrix on top of the stack is iden-
       tical to the one below it.

       glPopMatrix  pops  the current matrix stack, replacing the
       current matrix with the one below it on the stack.

       Initially, each of the  stacks  contains  one  matrix,  an
       identity matrix.

       It  is  an  error to push a full matrix stack, or to pop a
       matrix stack that  contains  only  a  single  matrix.   In
       either  case, the error flag is set and no other change is
       made to GL state.


ERRORS

       GL_STACK_OVERFLOW is generated if glPushMatrix  is  called
       while the current matrix stack is full.

       GL_STACK_UNDERFLOW  is  generated if glPopMatrix is called
       while the current matrix  stack  contains  only  a  single
       matrix.

       GL_INVALID_OPERATION   is  generated  if  glPushMatrix  or
       glPopMatrix is executed between the execution  of  glBegin
       and the corresponding execution of glEnd.


ASSOCIATED GETS

       glGet with argument GL_MATRIX_MODE
       glGet with argument GL_COLOR_MATRIX
       glGet with argument GL_MODELVIEW_MATRIX
       glGet with argument GL_PROJECTION_MATRIX
       glGet with argument GL_TEXTURE_MATRIX
       glGet with argument GL_COLOR_STACK_DEPTH
       glGet with argument GL_MODELVIEW_STACK_DEPTH
       glGet with argument GL_PROJECTION_STACK_DEPTH
       glGet with argument GL_TEXTURE_STACK_DEPTH
       glGet with argument GL_MAX_MODELVIEW_STACK_DEPTH