r_subdivisions for Doom 3?

[adjasont]

I'm not at my gaming PC right now so I can't try the ACTUAL Quake 3 command for it, but does Doom 3 has any command similar to Quake 3's r_subdivisions to simplify the game's geometry?

I ask because after some experimentation I think it's the complex geometry, not the game's special effects, that are causing the massive framerate dips on my PC.

[Wobbo]

No, sadly, from what ive gathered the polys in doom3 are totally fixed, so that there are no problems with the shadow drawing

teh curves are the same level of detail on all computers

[Sephiroth]

if anything you are running on an older system. try updateing drivers and such, it helps out alot. also if you use ATI cards, or ati based cards, there is a addon which speeds things up. unpacking can help loading levels faster, but you lose MP.
doom III is not quake3, it has alot of similar things, but is a new engine. think windows98 and windows 2000/XP look and do similar things but based on differnt programing

[Udderdude]

From what I've seen, setting r_shadows to 0 will give you a huge FPS boost, also removing any shadows. It's worth turning off if you just want to play the game and don't care about shadow effects.

[Mogul]

Clarification --


You can't turn off all shadows, just certain ones. There are some shadows that cannot be removed with that command, and probably can't be removed at all.

[adjasont]

Turning off r_shadows seems like the only way to reduce those framerate "pits" and it's my suspicion that it's because it's one of the few commands that actually reduces the number of polygons on the screen (shadows are, I would assume, polygons themselves).

To me that paraphrase from iD explains a lot. By emphasizing dynamic shadows they are dramatically increasing the polygon count (or something to that effect). Many modern games go out of their way to have dynamic LOD to reduce the polygon count which keeps the framerate somewhat steady in almost any indoor setting, but in Doom 3 if you look down a corridor and see a second room with its own detail you can pretty much count on your framerate dipping way low. The only default polygon reduction seems to be the culling that occurs on objects the player simply cannot see. Someone enlighten me if I'm wrong.

Try this experiment if your processor is somewhere around 2Ghz or less: find a point of view in the game where your framerate is at or close to its lowest point, one where you can just sit and stare (I have one point where I can stare with the flashlight on and it consistently sits at a framerate that dips down to 15FPS). Now, quicksave the game at this point and start tweaking some settings (do a vid_restart after each change). What I noticed is that almost without exception, ALL non-polygon related commands had no effect whatsoever on that framerate. I even cranked the resolution up one notch and added 4xAA and 8xAF. No matter what I did it stayed at that same exact framerate EXCEPT for when I turned off shadows.

AA is a very videocard-dependent feature, AF is a very videocard-dependent feature, and resolution is a very videocard-dependent feature. So I'm guessing I am extremely bottlenecked by something OTHER than my videocard. Obviously the likely culprit is the CPU or something directly related to it like the FSB. My specs: I'm running an Athlon XP at 2GHz on a KT133 chipset (20x100) with a Radeon 9700pro.

So again, if anyone knows of a way to cut out more polygons without screwing up the game TOO much, be sure to let me know ;) I'll try messing with the shadows, but it'd be a shame to lose them.

One thing this means is that maybe it's not enough to simply say "Doom 3 is naturally going to have crappy performance because it's using a state-of-the art engine." The engine is only partly to blame. As you can see, all these fancy features like bumpmapping and specular highlighting amounted to a hill of beans in my case; my card can handle it, and my CPU can handle it. What really seems to kill me, in this case, is more of a design decision: those darn dynamic shadows, and all that that implies.

[Deathmatcher]

adjasont said:

What I noticed is that almost without exception, ALL non-polygon related commands had no effect whatsoever on that framerate. I even cranked the resolution up one notch and added 4xAA and 8xAF. No matter what I did it stayed at that same exact framerate EXCEPT for when I turned off shadows.

AA is a very videocard-dependent feature, AF is a very videocard-dependent feature, and resolution is a very videocard-dependent feature.

You know, that AF comes automatically with high quality mode? So, if you turned on AF in the driver specs of your video card, you may have not noticed a performance difference, due to the fact, that it´s activated in the game anyway (on high quality). Try medium quality if you haven´t already.
Btw, how much RAM do you have?

[AirRaid]

The R_Shadows cvar controls stencil shadows. These are drawn and held in the Stencil buffer on hardware that supports it, which your card does. Stencil shadows do not "add polygons" into the scene, indeed, any areas which fall inside a shadow which make the area completely black are simply not drawn at all. This actually reduces the number of polygons the game needs to draw, but the calculations required to produce the shadows are very video-card intensive, which does cause a drop in framerate in some areas.

In all honesty, you go on about the number of polygons in Doom3 but it isn't that detailed really. I've seen systems with far lower video meory bandwidth and CPU speed crunch them just fine, so I would suggest that the problem lies somewhere with your system, not with the game. You should be able to run the game playably at medium settings with no problems. Are you using the latest ATI Driver release? I know it had some fixes to help specifically boost Doom 3 performance.

Edit: BTW IMO AA and AF are totally unnecessary in Doom3. I've never come across a single place where textures are ugly due to lack of AF, and AA only serves to slow your framerate down where it's not really needed.

[toxicfluff]

AirRaid said:

Stencil shadows do not "add polygons" into the scene, indeed, any areas which fall inside a shadow which make the area completely black are simply not drawn at all. This actually reduces the number of polygons the game needs to draw, but the calculations required to produce the shadows are very video-card intensive, which does cause a drop in framerate in some areas.

This is not true at all. A surface has to be cut up for a shadow to be projected onto it. So when you have a monster casting a shadow onto a square floor (usually 2 polys) for instance, that floor gets cut into many many more polygons for the monster's shadow to be rendered on it.

You can test this easily yourself by launching the game, typing "r_showprimitives 1" in the console and then using "spawn light" to spawn more lights. The "tris" column is listing the total polygons are in the current scene, and the "shdw" column lists how many of these are caused by the shadows.

[adjasont]

Deathmatcher said:

You know, that AF comes automatically with high quality mode? So, if you turned on AF in the driver specs of your video card, you may have not noticed a performance difference, due to the fact, that it´s activated in the game anyway (on high quality). Try medium quality if you haven´t already.
Btw, how much RAM do you have?

Yeah, I was tweaking the AF setting using console commands and vid_restart so I was able to compare directly what things looked like with it on and with it off. Im not saying AF doesn't drop your average framerate; it does, but what it DOESN'T do is push my rock-bottom framerate any lower than it already is. It's only going to limit my peak framerates. For that reason I don't mind using it in-game, because I don't care if my 55fps moments get pushed down to 47. At my system performance level what I'm most concerned with are those 15-20fps moments, and AA/AF/resolution don't seem to be adding much to that (the bottleneck is elsewhere).

I have 512MB of RAM. Doom 3 is very playable for me. However, it does have more "chug" moments than most games (as expected). All the benchmarks I've seen online with "minimum framerates" listed seem to confirm this. I'm simply trying to figure out what's going on during those moments and how to alleviate it. Even relatively high-end systems seem to have their slow moments (perhaps this is during intense battles though; mine happens even when I look at a particularly heavy scene).

[AirRaid]

toxicfluff said:

This is not true at all. A surface has to be cut up for a shadow to be projected onto it. So when you have a monster casting a shadow onto a square floor (usually 2 polys) for instance, that floor gets cut into many many more polygons for the monster's shadow to be rendered on it.

You can test this easily yourself by launching the game, typing "r_showprimitives 1" in the console and then using "spawn light" to spawn more lights. The "tris" column is listing the total polygons are in the current scene, and the "shdw" column lists how many of these are caused by the shadows.

Sure, over a flat surface. But over complex geometry the number of polys being drawn should decrease, since the few being chopped to make the shadow shape are less than the number being obscured by the shadow.

Or maybe I'm getting my shit mixed up. I haven't slept much and im wrestling with a broken keyboard here.

[Udderdude]

I fooled around with a few cvars to see if I could reduce the shadow detail ..

seta r_sb_lightResolution "64" // default 1024
seta r_sb_viewResolution "64" // default 1024
seta r_sb_samples "1" // default 4
seta r_sb_linearFilter "0" // default 1

All of these settings did nothing. The scene I was using stayed at 20 FPS no matter what I did. Of course turning off shadows it was 60 FPS ..

There really should've been a way to reduce the shadow detail without removing them completely, since they can really bog down a scene.

[RamboBones]

In case anyone is interested stencil shadows work in the following way, I'll be explaining it for a single light. Main geometry is rendered as if shadowing doesn't exist using all other lighting calculations. CPU is used to calculate the silhouette of objects for projecting shadows. Shadows are then drawn as black, or near black, polygons. For multiple lights all the shadows must be re rendere'd, and re-calculated for every light.

Btw, I am a programming and have done stencil shadowing in the past so I do know what I'm talking about, however I have of course explaining it very simply.

[Wobbo]

AirRaid said:

Sure, over a flat surface. But over complex geometry the number of polys being drawn should decrease, since the few being chopped to make the shadow shape are less than the number being obscured by the shadow.

No, its even WORSE over a 3 dimensional surface, the game has to render the gemoetry BEFORE it culls things out

One of Carmacks .plan files specifically states that the shadow z-axis optimization is *NOT* made in doom3