One could texture a whole level with a 256x256 texture i.e., but what should be the resolution of a texture to be called MegaTexture? How much should you zoom until you see the pixelation?Originally Posted by NecroDOME
YYou should also implement MegaTextures (id Tech 5 uses them) It's per-triangle unique texture.
mega texture would more define a 16.000x16.000 texture
NecroSOFT - End of line -
the MegaTexture technique by John Carmack. :)
altough the idea isn't really groundbreaking, you at least have to find a
speedy way to implement the streaming, unless you're generating the textures at runtime (farbrausch, anyone? :D)
I think the biggest positive on having an engine that streams the texture-data is that - providing it works *g* - you never ever have to think about handling texture maps again, because you get vram-size-independency. :D
http://en.wikipedia.org/wiki/Megatexture (link fix)
And how is the technology of MegaTextures working? I can think about it as dividing the mesh in several pieces (the visible ones), loading the texture fragment for the corresponding meshes and rendering (paging). Might not be that simple, or does it? Also, if U-V coordinates are values from Single(0.0) to Single(1.0), isn't it a problem to deal with that huge resolution (128000x128000 pixels) to map the meshes? There should be a limit regarding to floating point precission. Or is it possible to feed the U-V with practical values larger that 1.0? :?
its more that they divide the texture into a grid of all textures needed for a render call. (according to this thread @ GameDev.net http://www.gamedev.net/community/for...opic_id=460053)
They have some textures where they put up the mipmaps and textures used for that render call. As carmack said: we can render the entire scene in 3 render call (don't ask me how) if we disable culling n stuff...
First something about the relief demo. Shaders ARE and probebly will always be faster to produce such results. Simply because the transformations that need te be applied to the massive ammounts of triangles is extreme. And todays cards are more build towards shaders then vertex processing. One thing I`m working on right now is using opengl geometry shaders to procude the same result. Just render the quads normaly and pas the heightmap and texture down the geometry and pixel shaders. Use the color texture to generate the pixel color and the heightmap to generate the traingles on the surface. Will hopefully finish this somehere this weekend.
And a thing about the megatexture. I have actualy studied this technique. There is a mod for the doom 3 engine available unlocking this.
http://quake4.filefront.com/file/Meg...ogy_Demo;72878
The shaders used for this technique can be extacted from the pakfile. The same goes for the Quake Wars beta if you have it. Once I took a look at the shaders the techique isnt really that hard. It is basicly the same is clipmapping. Here is a screenshot of clipmapping on a terrain surface.
http://gameprog.it/hosted/typhoon/te...rrainWire2.jpg
As you can see the further away the camera is the les striangles are used in a quadlike manner. Moving the camera arround just moves your quad boundaries arround. the can be streamed from the harddisk very effeciently. Megatexture does basicly the same but then in on a texture level. Instead of quads of detail on the geometry carmack uses 3 texture buffers of 512, 1024 and 2048. These are then filled From a base texture of 32*32 k . The large one is used up close and the others are used the further away you get. Here is a screen of the result with texturing instead of geometry.
http://doom3.filefront.com/screenshots/File/72779/4
The shaders for this are actually pretty easy. What I want to know is how he streams the new texture date in memory and how that he compresses a 32000 x 32000 pixel texture in 500 mb. (size in quake wars).
One thing I did discover in the quake wars files is that they also use detailtextures for up close with a coveragemap allowing up the 3 textures.
Also I found an engine a while back the could render terrain using the similar technique. ALso L3DT, the terrain generator I use has this technique implemented in it`s viewer.
http://www.bundysoft.com/coppermine/...album=22&pos=5
Like al stuff Carmack makes, someone thought it up a long time ago, he`s just the first to effectively use it and make it mainstream. (BSP, static lightmapping, stencilshadows, normal mapping enz)
@Luuk van Venrooij, That pretty neat stuff. Never gone in depth on terrain render or mega textures, but I well interested in the technique!
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