ATI vs Matrox Environmental Bump mapping

[ChrisDent]

From Anandtech's article on the Radeon 256
http://www.anandtech.com/printarticle.html?i=1230

"The difference between ATI’s EMBM solution and Matrox’s is that, instead of forcing developers to create a separate bump map texture in order to achieve the effect, the Radeon 256 applies the effect on a per pixel basis. The result is an easier time for developers and a more efficient way of performing EMBM than Matrox’s solution"

Can someone please explain to me what the difference is between the two implementations.

How can developing for the Radeon 256 be any different from developing for the G400? (I thought microsoft simply says what the API call looks like and if you follow the ms spec the result should be the same no matter what the end hardware is)

[box]

Me too?

How can you have bumps with no bump map, or am I missing something???

If they just extrapolate the bumps from the color-texture, then isn't this a step back for image quality, I mean in 3d-rendering you would never use the color map as a bump map (or seldom)??

BTW DENT asking about BUMP maps... Coincidence... I think not


[This message has been edited by box (edited 27 April 2000).]

[Gurm]

Do tell, anyone who knows.

Per-pixel bump mapping? I'd LOVE to know how that happens.

Although they may be referring to per-pixel ENVIRONMENT mapping. This could be niggling, and playing semantics. You can in fact do reflections and whatnot (half of EMBM) without a separate bump map.

So it wouldn't be environment-mapped bump-mapping, it would just be environment mapping. Which would be silly, since it would be a gazillion times easier to just make a reflection.

Or am I completely confused?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Corwin_Brute]

Dot3 bumpmapping only needs 2 textures, I think. It has a very, very good quality, but is harder to program than EMBM, and does not allow for other effects than bumps (that is to say no water, no heat shimmer...).

As for Anand's statement, the writer makes a fine mess between different bump mapping methods, that's all I can say. Had he done his homework, he would have found out that EMBM is a DirectX function requiring 3 textures : base texture, bump map, environment map. That's all. Not very professionnal...

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Corwin the Brute

[Dyre]

Im starting to question AnAndtech's findings... For one, they give video card benchmarks using resolutions like 640x480 and 800x600, where new vid cards simply fly and no-one should even care about these scores anymore. If you're looking to buy a GeForce2 GTS to run in 640x480, 800x600 or Even 1024x768 you really need to re-evaluate your standards and why you are dropping $350 buck on a vid card.

Second Grip: They can't get a G400MAX running on an Athlon? WTF IS THAT?! Should i trust someone about hardware when they can't even set thier sh*t up? Hell, i've got a MAX and a regular G400 working great on a couple Athlon system's first damn time i booted them....

It really makes you question if they are staying objective. Or worst, they are just falling WAY behind the tech curve, when they can't even set up a 3rd gen, year old video card on a new CPU platform.

[Dyre]

Im starting to question AnAndtech's findings... For one, they give video card benchmarks using resolutions like 640x480 and 800x600, where new vid cards simply fly and no-one should even care about these scores anymore. If you're looking to buy a GeForce2 GTS to run in 640x480, 800x600 or Even 1024x768 you really need to re-evaluate your standards and why you are dropping $350 buck on a vid card.

Second Grip: They can't get a G400MAX running on an Athlon? WTF IS THAT?! Should i trust someone about hardware when they can't even set thier sh*t up? Hell, i've got a MAX and a regular G400 working great on a couple Athlon system's first damn time i booted them....

It really makes you question if they are staying objective. Or worst, they are just falling WAY behind the tech curve, when they can't even set up a 3rd gen, year old video card on a new CPU platform.

[Stringy]

Well Tom of Tom's Hardware tried to explain this quandry that Anand seems to have created...
check out the reveiw, and also where he even Quotes that passage in the reveiw...
http://www7.tomshardware.com/graphic...427/index.html
http://www7.tomshardware.com/graphic...force2-07.html

Craig

[The Rock]

Voodoo Extreme has a write-up on the Radeon with some info on bump mapping.
http://www.voodooextreme.com/hw/Feat...iew/index.html

Embossed:

Here's the lowdown on Emboss bump mapping from ATI:

"The simplest and easiest, but also least realistic method is called emboss bump mapping. This effect is accomplished by taking a height map texture, shifting it away from the light source, and subtracting the shifted version from the original to produce a bump map. The bump map is then combined with the base texture. Emboss bump mapping is the easiest to implement because it does not require that special texture formats be used like other bump mapping methods"

Dot Prodoct 3:

"A more accurate and flexible version of bump mapping is Dot Product 3. It works by using a specially formatted bump map texture. Each pixel in the texture includes a 3D vector that represents the slope of the surface. A vector is then generated pointing from each pixel in the bump map to the light source, and a dot product operation is performed between this vector and the vector contained in the bump map to determine which direction light will be reflected off of the surface. This method allows control of the bump map down to the individual pixel level, which can give the appearance of a highly detailed surface when light is applied."

The Rock
www.3dforce.com


[This message has been edited by The Rock (edited 28 April 2000).]

[Jorden]

Maybe someone found out how to pixelate using bumps on chars? Can you bumpmap chars, where chars stand for the normal ABCDEFGHetc. characters?

Looking at this article, and that in the old days we could program our C64's and Amiga's on a pixel-perfect charset, I wonder.

Only question remains, can you bumpmap chars?

Jord.

[Himself]

I don't get where there is an ATi vs Matrox issue here, ATi supports EMBM and Dot3 according to all the previews out there, if some fool was comparing EMBM with Dot3 and saying the boards were different because of that, they are out of the loop.

[Gurm]

Himself,

No the problem is that there was this claim that ATI somehow magically did a per-pixel EMBM without a bump-map... which is patently absurd.

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Himself]

Heh, I read on usenet today about how one card was better at removing all the antialiasing from an image than another, lots of boneheadedness out there.

[Storm]

I have a pretty good idea of how ATI's EMBM is different. The way Matrox uses its EMBM is through the use of 2 textures. One being the map itself, the other being the height map (bump map) where the brightest color would equal the biggest 'bump'. It's grayscale of course, since there is no point in using the separate color channels for anything. ATI claims to be able to do EMBM using one texture. The only possible explanation for that, is basically taking the original texture, converting it to grayscale (or just get the overall luminosity values) and apply it to the object as a Bump Map. This has an advantage and a disadvantage. With this method, you Can't specify certain texture coordinates as being the bumps, BUT almost Every single stone/wall/wood/whatever texture doesn't need to have a Different bump map to look realistic. So basically, I think ATI just extracts the luminosity values from the texture and uses it as a bump map. This would Considerably save your texture memory, especially if the whole game is full of bumpmapping. If you mix the two methods together, you would get the best visual effect at the lowest frame rate expense. It's cinch to impliment in hardware, since it's hardly even 'color conversion'. I'm surprised Matrox didn't support it.

I *could* be wrong... well... no, not really.

PS: 3D Apps have always used that method for bump maps. You can have the bump map and the texture map share the same file, which is more than just convenient.

=Storm=

[This message has been edited by Storm (edited 29 April 2000).]

[Rob M.]

I'd just like to point out a couple of things. First off, a 256 greyscale pic does not take up anywhere near a 32 or even 16 bit colour pic.

Also, if you tried to extract the bump 'height' by luminosity, the texture artist would be severly limited in his/her ability to properly make the texture look correct/have proper bumpmapping.

Personally I think sharky was just making it all up. ATI surely implemented EMBM the same as Matrox, as it's all done through DX7..

Rob

[red2]

Matrox EMBM requires three passes, texture, bump, and gloss. The gloss is generated on the fly which may help to explain the "plastic" look of some EMBM shots. Also this helps programmers because they do not have to create the gloss map. Matrox EMBM shots generally only use like 2 triangles. One for the texture and one for the bump. So does ATI use more to do the per pixel basis? If they do, it sounds like a real bitch to program. Maybe Haig can clarify this.