Radeon shall have no fog table emulation???

[Scipio]

Problem: I have a ATI Radeon card but I can not see any fog graphics on my PC with Windows installed.

Cause/Solution: This is a problem with the drivers that ATI makes for Windows based systems. For some reason they have decided to not support "fog table emulation" which is needed to show the fog graphics in CMBB.

I found this on the FAQ page. Now I'm seriously surprised. From other games I often read that hints about performance issues that tell me to en-/ or disable the fog table with RadeonTeaker program (what is indeed possible, but with no effect in CM) - so I assume the Radeon has one? BTW, is the 'fog table emulation' not a part of DirectX, too, even in Version 6.x?

Sorry if I'm wrong

[ July 01, 2003, 03:45 PM: Message edited by: Scipio ]

[Thomas Norton]

Scipio, go down to the "Cat 3.5 by ATI-Still Broken." post, by Harv.

Matt, has told me that ATI does not want to support it. I hope that ATI will reconsider.

It is a code issue, and if they wanted too, ATI could make the fix though one of the upcoming CAT release. ATI plans to release a new CAT every month after the 3.6, which includes HOT fix for games issues. Well, this is my HOT issue with my number one game. Sadly, most of the attention is going to the FPS games.

Tom

[Scipio]

Well, I asked those who should know : ATI (producer of the Radeon chips). The answer was short and simple : Radeon cards can support fog table emulation via DirectX. Sounds to me like they won't include it into new drives, cause it ain't necessary. Does this mean that Radeon users have to wait for the engine rewrite, what means 2+ years?

[Thomas Norton]

Yes, but, ATI could make it work now. I wonder why they are not forthcoming on it?

[Redwolf]

CM uses a stone old variant of DirectX on Windows and the equally ancient Rave on MacOS.

The Mac users are more screwed because Apple dropped that APi entirely.

But the fact that Microsoft does still support these old DirectX versions does not neccessarily mean that Graphics hardware vendors actually fill the functionality provided by MS with working hardware control. Witness the ATI fog problems and a gazillion of less systematic problems with NVidia.

CM is just living on the edge with its choice of graphics APIs and very soon we will see NVida stop providing this support, too.

[Schrullenhaft]

The version of DirectX has nothing to do with these problems regarding fog effects. The CM series can probably run on a version of DirectX dating to 6.1 (though CMBB has 8.1 as the recommended minimum). Newer versions of DirectX have primarily added new shading and rendering specs that CM hasn't been programmed to use. Since CM uses 16-bit color for performance reasons (24/32-bit color textures would be A LOT larger), many of these new DirectX features can't really be used. CMX2 will be programmed to support 24/32 bit color, which also increases the capability to use effects that require those color depths (lighting effects, etc.). However there is a chance that CM will be programmed in OpenGL for both the Mac and Windows platforms.

If you're looking for more info about the subject of fog-tables they are also often known as Particle Fog (or Effects) in some literature. For fog effects in DirectX games ATI relies on 'Vertex Fog', which wasn't very well supported when CMBO came out (only a few cards did it, compared to the majority that supported fog-tables in one manner or another). There has been no perfect way of supporting fog in CM with just one render type (and I assume that it would have been A LOT of work to have CM offer more than one render type of fog).

I can't really give an accurate description of the differences between vertex and particle/table based fog, but from the dated screen shots I have seen directly comparing these two methods, particle/table fog was a bit superior in appearance (depth, fading, no 'banding' in particle fog). A more up-to-date comparision may show less of a difference however (such variables as newer drivers and hardware and a variety of other display quality settings could make the difference almost negligible). But it is speed that is probably considered the most important aspect of supporting features for today's games, so trading a small quality difference with fog appearance for speed is probably a worthwhile sacrifice for many programmers.

From what little I can find about it, apparently supporting fog-tables by emulation (which is what NVidia and some other cards do) is not possible with some of the vertex acceleration that ATI has based the Radeon family on. Apparently this must only be true for the DirectX drivers (and possibly OpenGL ?) since the same cards with Mac BIOSes can emulate fog tables under RAVE. This seems to be a conscious choice by ATI: they excel at vertex acceleration and they've decided to only support vertex fog to maintain that speed. Once they support fog-tables/particle fog, they will lose a lot of speed with the two rendering types on screen (vertices and particles), plus add some further driver complications (I assume).

Edit: To clarify here a little. Including support for particle/table fog doesn't automatically reduce the card's performance under DirectX. It is when particle/table fog is displayed on the screen that performance will be reduced. With Vertex fog, the performance loss is substantially less (for a possibly less aesthetic fog). ATI has probably decided to stick with Vertex fog and not bother with emulating fog-tables since they just see it as a performance-robbing option.

For those people using 'tweaker' programs to add registry entries for 'W','Z', 'fog-tables', etc., not all of those entries make a difference to the driver and they're not expressly 'enabling' a feature of the driver. Sometimes they may help a game that looks to find out if a feature is supported before loading up the graphics (in which case the specialized graphic is missing/inappropriate, but the game still loads rather than halting).

From what I can tell ATI doesn't really have any intention of supporting fog-table emulation under DirectX. I don't know if Charles is going to use Vertex Fog in OpenGL for CMX2 or not, but I would guess at this rate that he may do that (since most of the popular video cards at that point will be capable of vertex fog).

[ July 03, 2003, 05:11 PM: Message edited by: Schrullenhaft ]

[Thomas Norton]

Now I know why Matt told me that ATI is not interested in supporting it. If it will reduce the speed of the card, and that is more important to ATI, then a few extra dollars. Thanks for the techno reasons.

Tom

[Scipio]

With all resepect to Charles - I know he has written the full CM code on his own and developed the 3D engine. But maybe BTS should consider to find an additional person to create the new 3D engine. I guess this would also decrease the developing time for CM2. And time is money!

I can understand that BTS won't piss off all the people with old & slow PCs, but does it necessarily mean that those with better PCs must suffer from this? This is a very personal view, but it sucks when I have a some thousand dollar machine, and my most prefered game has no benefit from it. From what I can see, CM doesn't works significant better then it did on my old 1000 MHz machine. Indeed I have now more problems then I had before.

[ July 04, 2003, 05:37 PM: Message edited by: Scipio ]