glOrtho - multiply the current matrix by an orthographic matrix
void glOrtho( GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble near, GLdouble far )
left, right Specify the coordinates for the left and right vertical clipping planes. bottom, top Specify the coordinates for the bottom and top horizontal clipping planes. near, far Specify the distances to the nearer and farther depth clipping planes. These distances are negative if the plane is to be behind the viewer.
glOrtho describes a perspective matrix that produces a parallel projection. (left, bottom, -near) and (right, top, -near) specify the points on the near clipping plane that are mapped to the lower left and upper right corners of the window, respectively, assuming that the eye is located at (0, 0, 0). -far specifies the location of the far clipping plane. Both near and far can be either positive or negative. The corresponding matrix is | 2 | |---------- 0 0 t | |right-left x | | | | 2 | | 0 ---------- 0 t | | top-bottom y | | | | | | 0 0 -2 | | -------- t | | far-near z | | | | 0 0 0 1 | where right+left t = - ---------- x right-left top+bottom t = - ---------- y top-bottom far+near t = - -------- z far-near The current matrix is multiplied by this matrix with the result replacing the current matrix. That is, if M is the current matrix and O is the ortho matrix, then M is replaced with M · O. Use glPushMatrix and glPopMatrix to save and restore the current matrix stack.
GL_INVALID_OPERATION is generated if glOrtho is executed between the execution of glBegin and the corresponding execution of glEnd.
glGet with argument GL_MATRIX_MODE glGet with argument GL_MODELVIEW_MATRIX glGet with argument GL_PROJECTION_MATRIX glGet with argument GL_TEXTURE_MATRIX
glFrustum, glMatrixMode, glMultMatrix, glPushMatrix, glViewport
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Last Edited: Mon, May 22, 1995