If two or more texture layers are needed per object, Kyro is at a disadvantage compared to GeForce in that multiple rendering passes are needed. GeForce is able to apply two texture layers in a single pass. It is only when there are three or more texture layers per object that GeForce resorts to multi-pass rendering. Figure 3 shows the two-pass and three-pass rendering performances of Kyro and GeForce2 MX. The absolute numbers are not as pertinent as the percentage performance degradation as the number of passes is increased from two to three. The performance degradation is 7% and 20% for Kyro and GeForce2 MX respectively.
Figure 3: Fillrate graph of emboss bump mapping ('3DMark2000')
The on-chip 32-bit mini-framebuffer permits multi-pass rendering to be performed at full 32-bit precision irrespective of the desired framebuffer color depth. Figures 4 to 6 are screen-captures of 'Serious Sam Test 2', a 'first-person shooter' being developed by Croteam. The purplish glow is composed of multiple layers of transparent, dynamic textures. The screen capture taken on a GeForce shows color precision errors due to multi-pass 16-bit rendering (figure 4). Kyro does not exhibit these artifacts (figure 5). Similar portions of the screen-captures are shown at 4x magnification (figures 6 and 7).
Figure 4: GeForce, 320x240x16
Figure 5: Kyro, 320x240x16
Figure 6: GeForce, 4x magnification, nearest neighbour sampling
Figure 7: Kyro, 4x magnification, nearest neighbour sampling