Can anyone explain this? Every generation of Nvidia card has had this problem that I've seen. I've seen it ever since the TNT, and now I'm seeing it on my GeForce 256 and Tod's GeForce 4.

Every time a game does a "smoke" or "mist" effect, the frame rate hitches and sputters. I'm not talking about wide-area volumetric fog, I'm talking about stencil-style localized smoke tricks. Examples to follow below...

This seems to be totally engine-independent. For instance, back in the TNT days I saw it in certain areas on the Quake-engine game Half-Life. On the GeForce cards, I'm seeing in the new games Arx Fatalis and Unreal II.

Examples:

Arx Fatalis: Certain scenes where there is supposed to be light streaming into a prison cell through the bars in the window. They've added a sort of "dust-hanging-in-the-air" trick as an atmospheric effect so that you can see the light shining through the bars. This causes the frame rate to hitch and sputter, even when you're really far down the hallway and the effect amounts to something like four pixels total on the screen. It even affects the CPU, screwing up your control input, making you over-rotate or slide past a doorway.

Unreal II: Early in the game, your head tech is giving you a tour of the ship, and he's smoking a cigarette as he leads you around the ship. Any time he's facing you and you see the smoke effect coming off of the cigarette, the frame rate hitches and sputters.

Half-Life: Any time there are multiple stencils on the wall, such as blood spatters combined with weapon hit stencils, if you walk up close to them so that they fill most of the screen, your frame rate stutters like crazy even though there's pretty much only one polygon on the screen. This isn't technically a smoke effect, but I think it might be related. I'm guessing that the wall stencils in Half-Life were done with a similar programming style as the smoke effects in these other games. And I also seem to recall certain smoke effects in the game causing the same problem.

Anyone have any idea why this happens, and if there are work arounds?

Well, not that this fully explains it... but smoke effects take a TON of processing power because every little sprite you are seeing has alpha and blend effects that have to be calculated. I don't know the full on math explanation, but that's what i've gathered from the boys here at work. I can see if i can get a full explanation if you're interested.

That'd be cool. I'd also be interested in knowing:

- Why there aren't ways to do this "on the card" so that you don't need to hog CPU to do it?

- Are there other non-Nvidia cards which don't have this problem?

One reason I'm concerned is because I intend to upgrade my mobo and video card when Doom 3 comes out, and getting around this problem will be one of my criteria for decision. In addition to "what's the best card for running Doom 3", of course.

Sorry for all the NVidia fans out there, but as far as I can see, the company has dropped the ball for the past YEAR. They simply let ATI hold the top spot for the past 8 months or so now, and now that they've released their new card (sort of), it seems that ATI's 9800 is still beating it. That might be the card you want to go for, Tony. I know I'm very happy with my AIW 9700

*edit*
I would check if I have that problem with smoke effects, but I don't have the games you've listed, and I can't remember off the top of my head if any games I own have much smoke in them. Does GTA3 have any?

I would check if I have that problem with smoke effects, but I don't have the games you've listed

I think it's going to depend on how the individual games implement the effect. For instance, perhaps some games implement it in such as way that it doesn't cause a performance hit. But I do know that it's a problem in more than one game, and more than one engine.

So you want me to forward this question to one of our 3D engineers, right? I could come up with all sorts of (completely false, yet extremely amusing) reasons why you're seeing a slow down. But I'll try to get something accurate for you based on the effect you're looking at.

Anyone attend GDC this pst week?

Bruno

Every time a game does a "smoke" or "mist" effect, the frame rate hitches and sputters.

I can believe that with modern graphics cards. Or do you mean that the smoke effect is on-screen?

Peter

nah, they only send a select few from LucasArts to that thing.... i think a total of 8 people out of the whole company got to go.

I find that quite surprising. I'd think that GDC would be an important event for a game company.

oh, it is... but it's expensive to send a bunch of people to the full conference. Only those that gain to learn anything (the best of the best programmers, modelers, scripters... etc) go and then come back to share what they learned with everyone else. Saves money by disseminating info that way instead of sending everyone. We do have a booth there though.

In reply to:

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I find that quite surprising. I'd think that GDC would be an important event for a game company.

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You'd think that... until you go and realize it's been taken over by Marketing Workshops.
It's really just a big excuse for copious drinking...

And in regards to your "smoking problem", I haven't noticed that on my Nvidia cards. I don't have it here, but this cigarette effect is a series of translucent particles? Whoa... I just reread your original post. The wall splatters in Half-life are translucent textures on a plane placed just above the world geometry... I've never had that jittering slow down you talk about with those.

Sorry, but I can't even think of what could be wrong in that case. Nvidia's cards have always been pretty good with translucency. The old Power VR chips, like in the Dreamcast... those had really bad overlapping translucency problems due to some crazy tile based rendering stuff. I'll bang on Unreal2/Half-Life when I get home tonight to see if I can't recreate this problem.

but this cigarette effect is a series of translucent particles?

I don't get the impression that it's a particle effect, no. I think it's something with sprites, more along the line of what Loren was saying. Not sure exactly, I don't know what's going on at the low level.

Crap... I typed up a reply to thing last night, but it didn't seem to stick.

Long story short... I tried to duplicate your slow down in both Half-Life and Unreal2 with no luck. They are both translucent sprites (the cig smoke is a sprite base particle effect) but I don't see why they would slow down too much. The only chip-set I know that has horrible problems with overlapping translucency is the old PowerVR... the one used in the DreamCast.

Sorry... uh...have you read the FAQ?

Sorry... uh...have you read the FAQ?

Nice. I love it when Tony gets FAQ'ed.

For a while, I thought this problem was solved. I was able to play all the way through Unreal 2 on my new GeForce FX without seeing the problem once.

Then I loaded up Medal of Honor: Allied Assault, and it happened really bad.

There are some scenes in the game where a tank or a gun emplacement gets destroyed. Afterward, there is a lot of smoke coming out of the wrecked tank or gun. The closer you get to the wreck (or if you view the wreck through your binoculars or sniper scope) the worse it gets.

I'm reasonably sure the free downloadable single player demo of Medal of Honor has this very thing happening pretty early on. So if anyone wants to check this on your own card, you can use the free demo level to do it (or if you have the full version of MOHAA, you can go to this level).

The single player demo can be grabbed here if you want to try it:

ftp://largedownloads.ea.com/pub/demos/mohaaspdemo.EXE

It's a big download, 183 megs, so it's only useful for those on really fast connections.

Anyway, the demo, if I recall correctly, is of the level where you're supposed to be destroying some german rocket launchers in a nearby town. This level starts off with you moving down a road toward the town and encountering resistance. There is a moment (again, if I recall correctly) where you have to shoot a half-track with the rocket launcher. After you nail the half track, it will be belching smoke. Getting close to the half track or zooming in with binocs/sniper will reveal the stuttering.

Note that I've got my all my graphics settings cranked because I've got a next-generation card/system and this is an old game. It runs perfectly smooth with all settings cranked except in this one odd instance.

Does anyone experience this slowdown on these parts of this game?

I'm asking for help because my goal here is to determine...

a) Does every Nvidia card have this bug always?
b) Does it also happen on ATI cards, or just Nvidia cards?
c) Is there a work around?
d) What exactly causes it and why? Is it something inefficient in the way they coded the game, or is it a bug in the drivers, or is it a hardware limitation?

i dont have this problem at all on my machine. i spent an agonizing four hours looking at all the decals, smoke and particle effects i could.

Cool! Which card are you using?

my 9700 aiw

Cool, OK.

So we've established that ATI cards don't have the problem... I wonder why Nvidia cards do?

cause im biased towards them. :P

So, curiosity got the best of me since I have a Nvidia GeForce 4600 Ti. I downloaded the MOHAA demo. I've played it several times and still don't know what it is I'm supposed to be seeing. Help me out here please.

Is it the banding across the top of the halftrack when you zoom in? Looks as though there are "waves" of smoke moving across the surface of the halftrack?

Comparatively speaking my system bites so maybe, I don't know what I'm missing in my gaming experience?

"So we've established that ATI cards don't have the problem... I wonder why Nvidia cards do?"

I'm not convinced we've established this is a Nvidia problem... I've used just about every generation of Nvidia since the TNT, and I've not been able to reproduce your problem on a GeForce2,3, or 4. (Neither have I been able to reproduce it on my ATI cards either.)

I'm starting to think it might be some other problem... could it be because you are still using win2k? Just a shot in the dark...

EDIT: Mach... I think he's refering to a frame rate stutter he gets when the screen is full of translucent sprites. I believe what you are pointing out is sprite clipping with world geometry... that is normal and sadly an artifact of the technique.

Is it the banding across the top of the halftrack when you zoom in? Looks as though there are "waves" of smoke moving across the surface of the halftrack?

No.

I'm referring to a significant drop in frame rate at that scene.

When playing other parts of that scene, I get 50-60 frames per second with all the detail settings cranked.

When I am looking at that smoke, I get about 3 frames per second on my old card and about 10-12 frames per second on my new card.

Are you getting a drop in frame rate there?

No I don't notice any stutter or drop in frame rate. Using GLexcess, my system is ranked low(2877) compared to yours so maybe I'm running at a lower frame rate initially and don't notice it as much? I don't think I'm seeing anything like 3FPS though.

Just bought Unreal Tournament 2004, and it does this same thing to me now, too.

Sometimes I can get it to go away by lowering the "Texture Size" setting in the graphic details. But this new card should have tons of texture memory and I should in theory be able to crank it.

Gonna mess with the settings and see if I can narrow it down to one specific thing...

buy an ati

My offer for a discounted card still stands.

Bruno

what kind of discounts are we talking?

Yeah, and for which card(s)? I need to finish my other gaming system before I order the rest of the equipment.

More information: It seems to be related to AGP texturing somehow, and specifically the texture sizes of player models and such.

For instance, on UT2004, if I lower the character detail so that the textures on the characters are irritatingly blocky, then it doesn't seem to happen. If I increase the character detail, I get hitches and sputters each time a character moves onto the screen from off the screen. It's as if it's having to reload the character's textures each time because it doesn't have enough texture memory on the card.

But I bought the card with the most texture memory (256). And I got an opportunity to try out an ATI card with 256 megs of texture memory, and it doesn't have this problem when plugged into my machine.

Besides considering an ATI card (which I am seriously considering at this point!) does anyone know of any driver settings that will improve the speed of these texture loads and prevent it from stopping the entire computer during the texture load?