Suppose a line between two points (x0, y0, z0) and (x1, y1, z1) crosses the left clipping plane (x = -1). To clip the line, we have to find a point at the intersection between the clipping plane and the line. A parametric representation of the x-coordinate is . As t varies from 0 to 1 the parametric equation computes the x-coordinate of all points on the line. The calculate the parameter t at the intersection with the clipping plane we solve the equation for t such that x=-1:


The coordinates y and z of the intersection point are computed by substituing this value of the parameter t into the corresponding parametric equations: