Thread level pre-emption will be available later this summer and performs similarly, but for CUDA computing tasks rather than graphical commands.
Simultaneous multi-projection (SMP) is a highly intriguing new technology that improves performance when a game needs to render multiple “viewports” for the same game, be it for a multi-monitor setup or the dual lenses inside a virtual reality headset. A more granular SMP feature can also greatly improve frame rates in games on standard displays by building on the groundwork laid by the multi-resolution shading feature already enabled in Nvidia’s Maxwell GPUs.
This fancy new technology’s at the heart of Nvidia’s claim that the GeForce GTX 1080 is faster than two GTX 980s configured in SLI. The card never hits that lofty milestone in traditional gaming benchmarks—though it can come pretty damn close in some titles. But it’s theoretically possible in VR applications coded to take advantage of SMP, which uses dedicated hardware inside the Pascal GPU’s PolyMorph engine hardware.
Displaying scenes on multiple displays traditionally involves some sort of compromise. In dual-lens VR, the scene has to have its geometry fully calculated and the scene fully rendered twice—once for each eye. Multi-monitor setups, on the other hand, tend to distort the imagery on the periphery screens, because they’re angled slightly to envelop the user, as shown above. Think of straight line drawn across a piece of paper: Folding the paper in half makes the line appeared slightly angled instead of truly straight.
Simultaneous multi-projection separates the geometry and rendering portions of creating a scene to fix both of those problems. The Pascal GPU calculates a scene’s geometry just once, then draws the scene to match the exact perspective of up to 16 different viewpoints as needed—a technique Nvidia calls “single-pass stereo.” Any parts of the scene that aren’t in view aren’t rendered.
If you’re using SMP with multi-monitors rather than a VR headset, new Perspective Surround settings in the Nvidia Control Panel will let you configure the output to match your specific setup, so those straight lines in games no longer appear angled and render as the developers intended. Sweet!
But that’s not all simultaneous multi-projection does. A technique called “lens-matched shading”—the part that builds on Maxwell’s multi-res shading—pre-distorts output images to match the warped, curved lenses on VR headsets, rendering the edges of the scene at lower resolution rather than rendering them at full fidelity and throwing all that work away. Like SMP’s single-pass stereo, the idea is to render only the parts of the image that will actually be seen by the user in order to improve efficiency.
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