glPopMatrix

C SPECIFICATION

void glPushMatrix(void void)

C SPECIFICATION

void glPopMatrix(void void)

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 two modes, GL_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 the top of the stack is identical 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. 彈出棧頂的矩陣，並將其刪除。這樣，原來從棧頂數位於第二位的矩陣將成為棧頂矩陣。當前堆棧由函數glMatrixMode( )指定。如果矩陣堆棧中只有一個矩陣，調用函數將導致錯誤。

ERRORS

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

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

GL_INVALID_OPERATION is generated if glPushMatrix is called between a call to glBegin and the corresponding call to glEnd.