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oil_on_glass

How many triangles can xbox 360/ps3 push per frame?

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Assuming that every polygon has multiple texture passes(color, normal, gloss, and specular coefficient, lightmap), and all the textures are high resolution 512x512 and 1kx1k how many polygons/triangles can xbox 360 and ps3 handle on a per-frame basis? thanks

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oil-on-glass, I can't answer your question specifically, because it is very unrealistic. First, an inaccuracy: color, normal, gloss, spec and lightmap should all be able to be rendered in a single pass. Only shadows and effects which look-up more than 4 textures (which couldn't be produced by math equations) should require multiple passes.

Second, it would be downright stupid for developers to render all polys with the same quality and texture resolution. High quality pixel and vertex shaders will be LOD'ed out 5-10 metres from the camera, and high rez textures are terrible for texture cache coherency; so they cost not only memory but per-pixel speed. 75% of pixels can be rendered at top-speed with minimal shaders without any appreciable difference in quality.

So, I couldn't begin to guess what "maximum possible" triangle count would be, but for a normal 60 FPS game: whereas for PS2 it was 50k - 75k, for PS3 I would guess 100k - 300k. Of course, that ballpark-figure alone should demonstrate how meaningless triangle count is... those foreground triangles will be dramatically shaded and dynamic in ways far beyond what shaders can provide (dynamics calculated by the insane extra CPU power).

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Relevant specs:

Xbox 360:

Polygon Performance - 500 million triangles per second

Pixel Fill Rate - 16 gigasamples per second fill rate using 4x MSAA

Shader Performance - 48 billion shader operations per second

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Why would you want to measure triangle per frame? I would assume it would be limited by the amount of memory in the system. If you want to measure the performance you would want to measure triangles per clock or per second.

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Quote:
Original post by teh_programerer
Quote:
Original post by parasolstars
correct me: essentially, xbox has a radeon 850xt gpu


It is indeed an ATi R520 Chip in the XBOX 360.


Actually it isn't an R520 chip its actually called Xenon and has a unified shader achitecture so you really can't compare it to a R520 its probably more like a hybrid R580.

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To clarify, the ATI GPU is not named Xenon, but Xenos. Xenon is the triple core IBM CPU. As has been said, the Xenos is not comparable to any current desktop GPU. The two primary distinguishing features are the Unified pixel/vertex shader units, and the 10MBs of INCREADIBLY FAST embedded framebuffer, which sits on a bus which is 2560 (yes, 2-5-6-0) bits wide and is what permits anti-aliasing to be essentially free. The technology does stem from what ATI intended to be the successor to the 9800 series, but for now they have simply chosen to modify and scale the 9800s basic technology on newer cards to maximize profit. ATI will almost certainly bring a desktop part out that will share many of Xenos' technology soon, but I would guess that's at least another generation or two out, 18-24 months or so. The Xenos also supports a feature set that is beyond DX9, but not quite DX10 either. The 360 equivilant of Direct3D also reflects this, though it is not directly derived from either API version.

Its hard to give a triangle count, but honestly triangle-setup has not been the bottle-neck for some time. GeForce4 generation hardware could setup something like 150 million triangles IIRC, but of course, that says nothing about how many you can actually draw. "triangles" has become irrelivant, nowadays its more about fillrate and shader perfomance.

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ravyne, is that all true?

I'm no GPU expert, but I thought multi-sample AA was done by running the pixel shader multiple times with slightly jittered samples within a pixel, then blending together the result. I don't see how the edram would make that faster, since still only the final result is written to the framebuffer... you have to run the pixel shader 4x as much, so that is the bottleneck over non-AA. I would see the edram helping mostly with framebuffer blends.

Anyway, does 10 MB seem smallish?

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