Punch-through techniques for graphics processing

Abstract

Techniques are disclosed relating to rendering graphics objects that require shader operations to determine visibility. In some embodiments, a graphics unit is configured to process feedback objects, which may require shading to determine whether they are visible relative to previously-processed objects, out of draw order. For example, in embodiments where a buffer is used to store fragment data for deferred rendering, the graphics unit may bypass the buffer and shade feedback objects ahead of earlier non-feedback objects whose fragment data is stored in the buffer. This may allow a determination of whether to remove occluded non-feedback fragment data from the buffer, which may reduce graphics overdraw. In disclosed two-pass techniques, data for feedback objects is first allowed to bypass the buffer for visibility shading, but is then stored in the buffer for a second pass to perform fragment shading to actually determine pixel attributes, which may further reduce overdraw.