*spin-off* idTech Related Discussion

[patsu]

... in the context of rendering. But the SPUs can do more (They are not "fully" utlilized yet). It's not the first time Carmack mentioned these good and bad traits.

 

[Neb]

... in the context of rendering. But the SPUs can do more. It's not the first time Carmack mentioned these traits.

Perhaps but they might fall really short vs 360 GPU overhead. It woud probably cost more to achieve the same with Cell/SPU than a dedicated GPU. Then it would leave less time of the Cell/SPU and perhaps short to handle the rest of gameplay logic which could lead to compromisses. .

 

[patsu]

It doesn't conflict with what he said: There is a little bit more headroom on the SPU side. Rendering is only one part of the game; important part but not everything. It's up to the devs whether and how to tap them. e.g., On the 360, they already need to handle extra decompression due to the DVD storage limit. At the same time, the freaking PS3 needs to deal with so-called better textures on the Blu-ray within its limited memory (probably more sophisticated Blu-ray --> HDD --> memory streaming ?). The consumers won't know what comes out of all these combo till the end.

Would be great if the devs can maximize the platform advantages.

 

[nightshade]

They would better achieve consistent performances as they plan to actually sell their engine.
Rage and Doom 4 have to be a showcase on every system available.

For the rasterizer comment I wonder if J.C just simply mean the GPU.

So he may be talking about just the rasterizer then ? & not the actual framerates at which the game runs ?
And I wonder why he said the CPU is on the same level...we know the PS3's GPU is on the short side but its the cell that compensate for it most of the time & I believe that is the reason we see almost like to like games on PS3 & 360.

 

[Scott_Arm]

What use would there be in having the rasterizer run at 60fps if that wasn't what we were going to see on screen? Isn't the rasterizer the final stage before output to the screen? I honestly don't know. This isn't meant to be smarmy and rhetorical.

 

[liolio]

So he may be talking about just the rasterizer then ? & not the actual framerates at which the game runs ?
And I wonder why he said the CPU is on the same level...we know the PS3's GPU is on the short side but its the cell that compensate for it most of the time & I believe that is the reason we see almost like to like games on PS3 & 360.

I guess it may depend on what they are doing. I remember that insomiac (or naughty dog I'm unsure ) had to secure two SPU for I don't remember which game even if they most of the time need between 1 and 1.5. maybe some of the stuffs they do require to block some SPUs on top of extra gpu work done on the GPU and that is leveraging the playing field.
Anyway his comment about the GPU let me think that it's more of a gpu problem, ie ID may have done what it take on the CPU side but may have overlook low level API optimizations on the GPU.
Anway, the title is far away

Actually I really hope to see more media for this game soon as all these technical problems are likely to be thing of the past when the game will launch somewhere in 2010.

 

[TimothyFarrar]

I'm not sure I buy into the 20-30Hz PS3 vs 60Hz 360 thing in that article, but yet I wouldn't be too surprised if it was true either. If so, sure would be interested in knowing the bottleneck.

I cannot imagine that they arn't using Edge and GCM by now (especially after Olick's presentation), even given a OpenGL code base which is likely easy to get going in PSGL. If not, well that might very well be a huge part of the reason. Also would guess that the fixed GPU/CPU memory split isn't in idTech5's favor (megatexturing), might force less than optimal placement of render resources.

From the SPU comments, sounds like they are CPU bound. PS3 mixes with PC devs like Apples and Hand Grenades. In fact the realization might have been something along the lines of this, "what do you mean I cannot just do arbitrary pointer referencing and pointer chasing all over the code, or have my objects interconnected into a ball of twine? ... we've been doing that for years, frag, the cost to change that practice now, well, we cannot just rewrite the entire engine, that would be astronomically expensive".

 

[bkilian]

The "4 DVD part" is not from edge article, it's computer and videogame own comment
They are misslead, 4 dvd is more than a single layer BR.

But because you'd have to mirror engine code and have multiple copies of textures in a multi-disc game, it's conceivable that the 360 version could need more space than the PS3 version.

The PS3 textures on Blu-ray are better because of the extra storage. So they may be trying to take advantage of the native strength of each platform. This is what I hope to see (He mentioned the SPUs have slightly more headroom in earlier interviews).

Carmack is talking about a snapshot of the build. We'll have to wait and see how their final system turns out.

The textures may be less compressed, but the PS3 has less overall texture memory available, so using a higher resolution texture may not be a smart move, since you would have to do a lot more texture streaming.

I expected some bull**** after reading that article, but not this much.

People should really grow up and also give id the benefit of doubt. It's not like their PC programming was messy or lazy or ineffective so why do some of you expect them to suddenly turn into lamerz??

But that's the problem. ID is a PC house in general, and Carmack has gone on record numerous times about how he prefers the 360's symmetrical architecture over the PS3 one because it's more similar to the PC, and thus easier for them to transition to for programming.

 

[TimothyFarrar]

The textures may be less compressed, but the PS3 has less overall texture memory available, so using a higher resolution texture may not be a smart move, since you would have to do a lot more texture streaming.

I'm going to bet with mega-texturing you actually need less texture memory. GPU sets limits on maximum single texture size BTW. So problem is likely more that CPU memory is pushed to a limit on PS3 (because you keep a cache of either read-from disk texture data at a good bit higher compression rate than DXT5, and/or a cache of re-compressed to DXT5 texture data in CPU memory)...

With extra GPU memory around on the PS3, then you get lazy and just fill it with something else that you might be tempted to stream, but don't because you no longer need to (and ideally you don't want to stream anything besides textures on consoles because after a few DVD seeks a second, arcade 360 owners will wet their pants as texture update slows down).

Regardless, Rage will kick ass!

 

[joker454]

I'm going to bet with mega-texturing you actually need less texture memory.

I haven't kept up on Rage as much as I should, but are they using megatexture for everything or only for terrain? In other words, are structures and characters still using regular texture methods, and only terrain uses megatexture? If that's the case then presumably available memory still has an impact on visual fidelity, albeit only on the non megatexture stuff.

 

[idsn6]

Rage extended virtualization to every surface, including non-terrain.

 

[joker454]

Rage extended virtualization to every surface, including non-terrain.

Ah ok, nevermind then. Looks like I have some catching up to do

 

[Brad Grenz]

I'm wondering if they're currently vertex limited on the PS3 and they are working towards moving the vertex load away from the RSX and onto the SPUs.

 

[Weaste]

I'm wondering if they're currently vertex limited on the PS3 and they are working towards moving the vertex load away from the RSX and onto the SPUs.

Isn't that what Olick and his staff would have been doing for a while? The engine has been in development for quite some time.

The RSX is slower than what we have in the 360. The CPU is about the same, but the 360 makes it easier to split things off, and that's what a lot of the work has been, splitting it all into jobs on the PS3.

That quote alone could support my guess, your guess, or many other guesses because it's so ambiguous.

 

[Weaste]

Take this with a big handful of salt, as it's from the Wikipedia article regarding iD Software's megatexture technology, and typically has no citation supporting the text.

id Tech 6 will use a more advanced technique that builds upon the MegaTexture idea and virtualizes both the geometry and the textures to obtain unique geometry down to the equivalent of the texel: the Sparse Voxel Octree (SVO). It works by raycasting the geometry represented by voxels (instead of triangles) stored in an octree. The goal being to be able to stream parts of the octree into video memory, going further down along the tree for nearby objects to give them more details, and to use higher level, larger voxels for further objects, which give an automatic level of detail (LOD) system for both geometry and textures at the same time. The geometric detail that can be obtained using this method is nearly infinite, which removes the need for faking 3-dimensional details with techniques such as normal mapping. Despite that most Voxel rendering tests use very large amounts of memory (up to several Gb), Jon Olick of id Software claimed it's able to compress such SVO to 1.15 bits per voxel of position data.

The main drawback of the Sparse Voxel Octree is the need for fast updating of the octree in order to represent dynamic objects. However, Jon Olick gave examples of alternatives which would not require this, but cautioned that their use would probably be better suited for id Tech 7. For id Tech 6, SVO will therefore be used for representing static geometry such as terrains and buildings. Dynamic objects such as vehicles and characters will be represented by rasterized polygons as is the case in most 3D games today.

It's talking about iD tech 6, not 5 that is to be used in RAGE, but it's not beyond the realms of possibility that the two share a common if differing approach. It would be nice to see a paper or presentation on how iD tech 5 handles its megatextures for comparison. The talk about LOD however may (or not) go towards explaining the flickering issues that were mentioned on the 360. Maybe the PS3 is using system that can process the octree better (Olick is specifically mentioned) but with the risk of a reduced frame rate? Did Olick change the PS3 version of the engine?

I know, it's all speculation, does anyone here know exactly how iD tech 5 is supposed to be dealing with megatextures?

 

[Richard]

From EDGE Magazine:

As part of our look at id’s new multiformat shooter-cum-driver Rage featured in the new issue of Edge, out in UK shops on Monday, we saw that the frame rate of the PS3 version currently lags some way behind the 360’s.

The 360 version matches the PC’s 60 FPS while the PS3’s framerate runs at just 20-30 FPS. “The PS3 does lag a little bit behind in terms of getting the performance out of it,” Carmack acknowledges.

“The rasteriser is just a little bit slower – no two ways about that. The RSX is slower than what we have in the 360. Processing wise, the main CPU is about the same, but the 360 makes it easier to split things off, and that’s where a lot of the work has been, splitting it all into jobs on the PS3.”

He is, however, confident that the PS3 version will match that of all other supported platforms: “Everything is designed as a 60 hertz game. We expect this to be 60 hertz on every supported platform.”

“The work remaining is getting it locked so there’s never a dropped frame or a tear, but we’re confident that we’re going to get that.”

Emphasis mine; quote in full from their website, but do visit for a (small) peek at a new screenshot.

Weaste: Rage is using id Tech 5 which does not use voxels: it's straight polys except there are no discrete textures.

 

[Tap In]

at what point do we say that unified shaders are making a difference? Is this it?

I rarely hear it mentioned at all anymore yet at release many supposed it might be a factor in overall performance.

 

[Gabrobot]

Brian from id Software posted this over at Shacknews...not that anyone paid attention.

So anyway, point is...

This is right from someone at id Software:

The problem is fragment processing on the RSX is significantly slower than on the 360 and virtual texturing uses a lot of fragment processing. Other parts of the engine, such as physics and AI run faster on the PS3, but anything that uses the GPU runs slower on the PS3.

 

[RobertR1]

Sounds like their engine and tech is GPU heavy which naturally tends to favors Xenos.

 

[joker454]

Brian from id Software posted this over at Shacknews...not that anyone paid attention.

People pay attention, they just don't want to believe it. Trust me, I've been there I wonder if they are very much benefiting from xenos unified setup, where they can do pixel operations freely even in vertex shaders. Likewise, you can do fairly powerful stuff on 360 with _fetch shader instructions if you are allowed to use them. Makes me wonder if they are skipping hlsl sometimes and taking direct control in certain shaders to do their megatexture dance, doing that gives you lots of very cool options with the 360 gpu.