glOrtho describes a transformation that produces a parallel projection. The current matrix (see glMatrixMode ) is multiplied by this matrix and the result replaces the current matrix, as if glMultMatrix were called with the following matrix as its argument: 2 right - left 0 0 t x 0 2 top - bottom 0 t y 0 0 -2 farVal - nearVal t z 0 0 0 1 where t x = - right + left right - left t y = - top + bottom top - bottom t z = - farVal + nearVal farVal - nearVal Typically, the matrix mode is GL_PROJECTION, and left bottom - nearVal and right top - nearVal 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). - farVal specifies the location of the far clipping plane. Both nearVal and farVal can be either positive or negative. Use glPushMatrix and glPopMatrix to save and restore the current matrix stack.
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glOrtho: man2/glOrtho.xml
glOrtho describes a transformation that produces a parallel projection. The current matrix (see glMatrixMode ) is multiplied by this matrix and the result replaces the current matrix, as if glMultMatrix were called with the following matrix as its argument: 2 right - left 0 0 t x 0 2 top - bottom 0 t y 0 0 -2 farVal - nearVal t z 0 0 0 1 where t x = - right + left right - left t y = - top + bottom top - bottom t z = - farVal + nearVal farVal - nearVal Typically, the matrix mode is GL_PROJECTION, and left bottom - nearVal and right top - nearVal 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). - farVal specifies the location of the far clipping plane. Both nearVal and farVal can be either positive or negative. Use glPushMatrix and glPopMatrix to save and restore the current matrix stack.