HSR Efficiency

What does this counter show?

This counter represents the effectiveness of the Hidden Surface Removal (HSR) engine, rejecting obscured pixels before they get processed. This tells you the percentage of pixels sent to be shaded, out of the total number of pixels submitted. Any pixel occluded by an opaque polygon and not visible is rejected at this early stage. This avoids the expensive processing and texturing of pixels that are not visible, maximizing processing performance and saving memory bandwidth.

What does a high value mean?

A value of 0% indicates that the number of input pixels in the HSR is the same as the number of pixels to be shaded, implying that no pixels have been rejected. The higher the value, the better rejection rate, achieving the associated performance and bandwidth benefits. For example, a 50% value means that half of the pixels have been rejected before being sent for processing. If this value is very low you should try to reduce the number of blended fragments submitted. It is also recommended to submit opaque draws before translucent ones, as this allows the HSR engine to reject occluded blended fragments. Bear in mind that a simple scene with very little overdraw might show a very small HSR Efficiency value as most pixels are visible.

A 100% value or closer is only possible when most of the pixels have been rejected by the depth comparison which should point to an application problem.