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View Full Version : Confused about the whole PPU thing.


Delbert
05-02-06, 02:18 PM
Can someone please explain to me what the PPU actually does.
My modest understanding is that it expands the ability on how dev's can make items interact with each other, and take the calculations about that interaction away from the CPU.
I always thought that it was the CPU that had to calculate the vertices of the items on the screen, pass this info to the GPU which would then render them to produce the lovely images we are so used to. Hence why the more polygons a game has, the more CPU dependent it was.
If the PPU is able to calculate the physics for 20000 items instead of say 20 for the CPU, is the PPU also sending the info on the vertices to the GPU for rendering, or does the CPU still have to do this ( might explain the drop in frame rates when PPU is activated ).
Now i have probably got the terminology all wrong, but i hope somebody cansee past my stupidity and explain it to the simpleton... plz...
Any good linky's would also be welcomed....:D

jolle
05-02-06, 02:58 PM
Basicly its just a dedicated chip to do the physics caluculations.
that about vertices and stuff like that was moved onto GPU from CPU back on DX7 with Transform&Lighting, where the GPU took care of setting up triangles and lighting them. (which is moved over to Vertex Shaders nowdays I think)
I spose somewhere down the line the CPU is involved in shipping data to GPU, but then you have things like geometry instancing for alot of identical peices of debris that can save a bit of work on GPU etc.

You will get a FPS penalty with the added objects in PPU enabled games (more work for GPU), depending on how much objects they add, but you get pretty heavy physics that prolly wouldnt run well without one.
The Cellfactor video on Ageias site is pretty impressive for example.

The chip itself is prolly pretty parallell, like GPUs are, and looking at the type of things the GPU does, its lightyears faster then a CPU at it, which should be true for the PPU and most other dedicated processors.
Coupled with fast GDDR3, since thats apparantly important for physics calculations aswell.

Monolyth
05-02-06, 03:21 PM
Also remember that ppu will be able to improve the quality of fluid dynamics in-game, allowing the motion of water and other substances to flow properly based on environment conditions. It's not such a big deal with older graphics considering everything was pre-rendered, with the sophistication and processing power of the newer technologies we can now fully interact with our environment instead of being forced to watch some pre-rendered sprite 'pretend' to do something.

The cost to the GPU will be minimal once the technology has been refined and games/apps built to FULLY support the features of the PPU.

At this time apart from demo's of Cellfactor we have not seen any game "rely" completely on the PPU, and probably won't for at least a few years. Until it becomes an integrated feature of GPU and/or IC integration I think that it will remain a 'flashy' addition to gaming with no huge backing, but still a very cool one.

Major acceptance of PPU will require big time support from major computer companies and the not-so standard standards baron Microsoft. If the rumors of MS developing a physics API are true then the PPU will have a future with integration into the newer DX generation we could see some REALLY cool PPU enabled functionality right on our desktops! Can we say truly "Fluidic" themes? :D Imagine clicking your Start "Bubble" and have it create a beautiful 3D ripple effect accross your desktop with your icons creating tiny wrinkles in the waveform. Flashy yes, but even I would think that was cool, and if the PPU/GPU did most of the work without affecting other functions why should I care? :D

dwhjr77
05-02-06, 05:18 PM
Don't waste anymore thoughts on this until 2008. It's useless, immature tech at the moment. It's a scam to get us gamers to buy more hardware. Every six months a blockbuster title is release only to be found out by unsuspecting gamers that they also now need another graphics card to compliment it.