//============================================================================
//
// Listing 9.1
//
// Mathematics for 3D Game Programming and Computer Graphics, 3rd ed.
// By Eric Lengyel
//
// The code in this file may be freely used in any software. It is provided
// as-is, with no warranty of any kind.
//
//============================================================================


void LoadOffsetMatrix(float l, float r, float b, float t,
		float n, float f, float delta, float pz)
{
	float		matrix[16];
	
	// Set up standard perspective projection.
	glMatrixMode(GL_PROJECTION);
	glFrustum(l, r, b, t, n, f);
	
	// Retrieve the projection matrix.
	glGetFloatv(GL_PROJECTION_MATRIX, matrix);
	
	// Calculate epsilon with Equation (9.7).
	float epsilon = –2.0F * f * n * delta / ((f + n) * pz * (pz + delta));
	
	// Modify entry (3,3) of the projection matrix.
	matrix[10] *= 1.0F + epsilon;
	
	// Send the projection matrix back to OpenGL.
	glLoadMatrix(matrix);
}