The range of depth values within the overlap of a convex polygon and a square or rectangular rasterization area can be determined by identifying whether the minimum and maximum depth values occur at the corners of the rasterization area or at intersections of the polygon's edges with the area's sides. By choosing between the corner and intersection for both the minimum and maximum depth limit, solving the depth plane equation at the chosen location, and clamping against the polygon's vertex depth range, a tight depth range describing the depth values within that overlap are obtained. That tight depth range is utilized to cull pixel values early in the pipeline, improving performance and power consumption.