Doom3world

Before it gets buried in the announcement thread I think this feature deserves it's own discussion.

Procedural Textures? Unique hand painted...???

Get it rollin

Fixed your subject -Burrito

Another discussion with some ideas over here

http://www.gamedev.net/community/forums ... _id=319912

Source: http://pc.gamespy.com/pc/enemy-territor ... 055p2.html

MegaTexture == ClipMapping(or ClipTexture)

in short, its a very enhanced or "virtual" MipMapping technique developed by silicon graphics (sgi).

"Real-time graphics applications can now use textures of any desired precision at full speed- examples include planet-wide textures from satellite data, contintent scale visual simulation applications with centimeter scale insets, architectural walkthrough applications showing murals with minute brush strokes visible at close inspection..."

really good sgi paper:
http://www.cs.virginia.edu/~gfx/Courses ... lipmap.pdf

sgi paper from 1996!:
http://www.sgi.com/products/software/pe ... _intro.pdf

description from sgi's developer library:
http://techpubs.sgi.com/library/tpl/cgi ... /ch15.html

an sgi example:

This image used ClipTexture to drape 0.5m image data onto an Active Surface Definition terrain with 5m elevation data.

doom3 references many of the same concepts in that paper:
r_showMegaTexture //display all the level images
r_showMegaTextureLabels //draw colored blocks in each tile
r_megaTextureLevel //draw only a specific level
r_skipMegaTexture //only use the lowest level image

i wonder if this technique was patented by sgi??? i hope sgi doesn't pull a creative labs on carmack!

also, i'm sure there's even more to it than what sgi did. we know that each surface type behaves different (less traction on gravel than on pavement for example). this leads me to believe that different material shaders are used depeneding on where you are on the Megatexture.

interesting stuff!

so now you can now use a single HUGE detailed texture for an entire landscape and not be hindered by system memory limitations.

this is not possible with current hardware simply due to memory limitations. todays engines allow for detailed textures (typically 512x512 or 1024x1024), but they would have to be tiled and repeated over and over to cover large outdoor terrain.

no longer. now you can have a single HUGE terrain texture the size of 65,536 x 65,536 or even larger! that's 128 times doom3's standard 512x512 texture size. WOW!!!

how is this possible??? the vast majority of the texture is stored on your hard drive, not in system or video card memory. so while you are playing the game, the engine will continually access the hard drive to pull the relevant MegaTexture pieces.

great stuff...

Not to burst your bubble but texture streaming off the HD has been available for a long time now, in fact, that's what the xbox has to do to make its games work on 64mb total memory.

I see a slight problem here - where are we supposed to store that sort of textures. I've got a "decompression bomb" PNG picture with 19000*19000 dimensions, which is supposed to weight 1GB when stored uncompressed. Now, if I'm not mistaking, a 65536*65536, 24-bit texture would weight... erm, 96GB..??!! Like, hard drive or not, this is insane. What am I missing here?

its not quite the same thing. this method is best for large landscapes that you can see.

texture swapping or streaming from hd for textures that you can't see (like textures in different rooms or areas) wouldn't be that hard. but i believe MegaTexture does it while you can see AND move around in the landscape texture.

well, maybe i got a little carried away, but its possible provided you have enough hd space...

I don't think you got carried away that much, i mean, consider how large would a single texture need to be in case you'd want to use it for terrain which covers such a large area. 64k*64k is not unrealistic at all, i mean, i've been using 1024 textures in some Q3 maps for a single room and you cannot just slap a 4096 texture or so for a far cry-sized map.

However, take a one or several GBs for a SINGLE TEXTURE - imagine what would a game weight if it contains like 10 maps... And what about downloadable maps? It's already impossible to download Doom MP demos, and now no custom maps?

Isn't the whole fuzz just about some small textures put here and there, as in strategy games (check the Warcraft 3 editor, or Pariah editor in that matter), or creating random textures on the fly, or pixel shader maps (3DMark03 pixel shader test)?

from brian harris at id:

From: brian@idsoftware.com
To: pbmader@********.com
Subject: Re: [D3M] The super secret(?) MegaTexture...

I can neither confirm nor deny the alleged rumours. You'll probably
find out more at Quakecon though.

-Brian

1.3 adds some MegaTexture-related cvars to Doom3... Take a look at the new cvarlist if you don't believe me

Please tell me it's not http://www.doom3world.org/phpbb2/viewto ... 3232#94576

pbmax: thx

pbmax: Is OpenGL patented? Will it ever be?

i read somewhere that they had a patent for it, but that could have been way back in 1996. maybe its not patented anymore.

in any case, perhaps jc's method is different just enough....

My guess is something along the lines of a base texture, basically a color with maybe a few splotches - and while in game the texture randomly adds a series of hundreds of decals of rocks, dirt, whatever, all over the area you're around... so off in the distance it LODs out to nothing (which means it's just drawing the underlying texture which is small and repeaty out in the distance and only drawing the decals in random order in a certain radius around the player).

Those texture clipmaps seem like the ticket, however the press release mentions crunching polygons too. From the conclusions of the clipmap.pdf:



A search for geometry clipmaps revealed:

At Siggraph '04 Losasso & Hoppe demonstrated geometry clipmaps (http://www.research.microsoft.com/~hopp ... lipmap.ppt) and Hoppe & Asirvatham demonstrated a new implementation primarily using the GPU (only decompression still uses the CPU) printed in the GPU Gems 2 book: http://developer.nvidia.com/object/gpu_gems_2_home.html. You can get the vertex/pixel shaders here: http://download.nvidia.com/developer/GP ... Index.html

The same paper presented at GDC '05: http://developer.nvidia.com/object/gdc_ ... tions.html (scroll down to download the presentation).

Aside from the intelligent use of the coarse poly grid, what caught my eye was that since the tesselation is constant (i.e. independent of terrain geometry complexity) performance is the same whether you have highly complex, variable terrain or a just a big plateau.

It'd be nice to get some kind of confirmation from id though.

Wouldn't that make it ClosedGL?

I got semi-confirmation. It's not Hoppe & Asirvatham's implementation but it might be the same thing.

@Mordenkainen

wow, nice find! polygon AND tecture clipping. i'm going to research this tech more.

by the way, where did you get your "semi" confirmation? i also think we'll get more info at quakecon.

awesome stuff...

ok, i found some more papers on geometry clipping:
http://research.microsoft.com/~hoppe/geomclipmap.pdf
http://courses.dce.harvard.edu/~cscie23 ... lipmap.pdf
http://research.microsoft.com/~hoppe/gpugcm.pdf

one question though: what LoD technique does te cryEngine use???