New-Tech Europe | November 2016 | Digital edition

at relative CPU time, this time we have recorded the relative GPU Vertex jobs time. Again, the smaller the better, regular stereo in blue and multiview in red. The savings are immediately visible on this chart as we are no longer computing most of the shader twice. Wrap it up From our measurements multiview is the perfect extension for CPU bound applications, in which you can expect between 40% and 50% improvements. If your application is not yet CPU bound multiview should not be overlooked as it can also somewhat improve your vertex processing time at a very limited cost. It is noteworthy that multiview is rendering to an array of textures inside a framebuffer, thus the result is not directly ready for the front buffer. You will first need to render the two views side by side, this composition step is mandatory, but in most cases the time needed to do so is small compared to the rendering time, and can thus be neglected. Moreover, this step can be integrated directly in the lens deformation or timewarp process. Multiview Applications The obvious way, and the one already discussed in this article, is to use multiview in your VR rendering pipeline. Both of your views are then rendered using the same draw calls onto a shared framebuffer. If we try to think outside the box though, it opens up a whole new field in which we can innovate. Foveated Rendering Each year sees our device screen

Fig. 6: Relative GPU time between multiview and regular stereo. The smaller the better, with the number of cubes on the x-axis and the relative time on the y-axis. Multiview in red, and regular stereo in blue

Fig. 7: Example of an application using foveated rendering

Fig. 8: A different reflection for each eye, demonstrated here in Ice Cave VR

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