One embodiment of the present invention sets forth a method for pre-computing Z-values using an IGPU and, subsequently, conveying these Z-values to a DGPU. The graphics driver partitions the display into rectangular M-by-N tiles of pixels. For each tile, the graphics driver generates a quad geometry that encompasses the corresponding pixels. For each image frame, the graphics driver configures the IGPU to generate and down-sample a Z-buffer, creating a coarse Z-texture that contains a Z-value for each tile. The graphics driver transfers the coarse Z-texture to the system memory and configures the DGPU to apply the coarse Z-texture to the quad geometries, thereby generating a coarse Z-buffer in which the M-by-N pixels included in each tile are assigned the Z-value for the particular tile. Among other things, this technique enables the IGPU to pre-compute Z-values for the DGPU without straining the system memory bandwidth or defeating the Z-buffer compression techniques used by the DGPU.