Although providing depth-buffer on-chip is a performance win. There is an option to enable an external depth-buffer. This is to maintain compatibility with applications that assume the existence of an external depth-buffer. 'Serious Sam Test 2' makes use of this property to determine lens flare occlusion. Figures 11 and 12 are screen captures taken with an external depth-buffer enabled and disabled respectively. 'MBTR' compares depth-buffer contents to determine shadow occlusion. Figure 13 and 14 are screen captures with an external depth-buffer enabled and disabled respectively. Ray-polygon intersection tests may be used instead for occlusion testing and are less likely to stall the graphics pipelines of both region-based and immediate mode renderers.