Patent ID: 7154499

Claim:
A method of rejecting a non-visible graphics primitive having a plurality of vertices, comprising: performing a logic operation on a first level to determine whether the graphics primitive lies outside of a defined area having a maximum x-value and a maximum y-value and being defined within a view frustum and rejecting the primitive if the primitive is outside the defined area; and if the graphics primitive is not rejected on the first level, performing a calculation on a second level to determine whether the graphics primitive is visible in the defined area and rejecting the primitive if it is not; wherein each vertex has a x, y, and w-coordinate value; and wherein the step of performing the logic operation on the first level includes: for each vertex, determining a sign of the x, y, z and w coordinates; comparing the y-coordinate to a maximum y-coordinate value and comparing the result to the sign of the w-coordinate to form a y-max result for the vertex; comparing the x-coordinate to a maximum x-coordinate value and comparing the result to the sign of the w-coordinate to form a x-max result for the vertex; comparing the sign of the x-coordinate to the sign of the w-coordinate to form a x-sign result; comparing the sign of the y-coordinate to the sign of the w-coordinate to form a y-sign result; ‘anding’ the x-max results of the vertices; ‘anding’ the y-max results of the vertices; ‘anding’ the x-sign results of the vertices; ‘anding’ the y-sign results of the vertices; ‘anding’ the signs of the w-coordinates of the vertices; and determining if any of the ‘anded’ results is true, and if so, rejecting the primitive.