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Re: Graphics

#36
DWMagus wrote:Ray tracing was brought to light again recently by CES. 'Nuff said.
From what I gather, they basically turned ray-tracing from a compute bound to a memory/storage bound problem? That's quite interesting and innovative.

But:
John Carmack wrote: Because ray tracing involves a log2 scale of the number of primitives, while rasterization is linear, it appears that highly complex scenes will render faster with ray tracing, but it turns out that the constant factors are so different that no dataset that fits in memory actually crosses the time order threshold.

Classic Whitted ray tracing is significantly inferior to modern rasterization engines for the vast majority of scenes that people care about. Only when two orders of magnitude more rays are cast to provide soft shadows, glossy reflections, and global illumination does the quality commonly associated with “ray tracing” become apparent. For example, all surfaces that are shaded with interpolated normal will have an unnatural shadow discontinuity at the silhouette edges with single shadow ray traces. This is most noticeable on animating characters, but also visible on things like pipes. A typical solution if the shadows can’t be filtered better is to make the characters “no self shadow” with additional flags in the datasets. There are lots of things like this that require little tweaks in places that won’t be very accessible with the proposed architecture.
Look at the sharp edges on the raytraced result in the youtube vid for example. Just getting soft shadows instead of hard shadows requires 25x - 100x the number of rays (depending on the quality and softness that you want). Their particular scene also plays into the classic advantages of raytracing (transparency, hard edges, high contrast elements, mirrored surfaces, low # of scene elements, etc) The render time goes up commensurately (as I can tell you from rendering even simple 3ds max scenes w/ soft shadows). Global ilumination and indirect lighting add at least another order of mangitude, depending on quality.

Not to say that their product isn't useful though. I for one would very much like to have such a card (though at a substantially cheaper price) for all the time that it'll save tweaking those stupid lights and exposure settings.

This video in contrasts uses a few more of those performance-hogging elements (don't think GI though).
http://www.youtube.com/watch?v=SLUvt_OPPvU

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