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Ehsan Kamrani
06-09-2005, 06:44 PM
As you know, we can use from the photoshop software to edit the pictures and use from multiple layers to attach multiple pictures to eachother.
Some books has simulated the lightmap with the multitexturing. But as i said before, we can use from photoshop to create a picture with the light effect and then use from one texture to simulate the *lightmap* effect.
So what's the actual application of multitexturing?
-Ehsan-

powerpad
06-09-2005, 09:40 PM
try a search for bump mapping and you will see what multitexturing is for (one example ...).

textures are there to add more detail to geometry (geometry that itself is often not that detailed) so textures simulate that in conjunction with other factors - lighting, ...

Overmind
06-10-2005, 01:17 AM
Typically you repeat the color texture over a surface. On the other you won't be able to repeat the lightmap, but it normally is a lower resolution than the color map.

So if you combine the textures offline, you would need a high resolution texture for every surface, but with multitexturing you only need a low resolution lightmap for every surface, and a few high resolution textures that are repeated...

The same argument works for detailmaps, that is a big low res texture over the whole surface and a small high res texture repeated over that.

And of course there are the advanced techniques where a texture doesn't neccesarily have to have color data in them, like normalmaps or bumpmaps in per pixel lighting... Not to mention fragment programming, where textures can contain really arbitrary data that can be used by your program in any way you like...

jide
06-10-2005, 04:51 AM
Originally posted by Ehsan Kamrani:
As you know, we can use from the photoshop software to edit the pictures and use from multiple layers to attach multiple pictures to eachother.
Some books has simulated the lightmap with the multitexturing. But as i said before, we can use from photoshop to create a picture with the light effect and then use from one texture to simulate the *lightmap* effect.
So what's the actual application of multitexturing?
-Ehsan-Okay, but what would have you done if the light or the object is moving ? Will you stop your program, run some photoshop or so, make your new image, get back to your program and update the texture ? :D

Reflexions, shadows, lights, shields, bullets on walls, LODS and so are some examples for multitexturing to exist and be powerful.

If all your graphics stuffs are static only, then you might use photoshop, even if generally, engines will create lightmaps: results are far more real and mathematically and physically right than with approximating them using any image manipulation programs.

Hope that helps.

Aeluned
06-10-2005, 05:22 AM
Just to beat a dead horse, here's an application of it you see often in games these days:

an subtle reflective environment map textured atop of the texture for the gun, or metal on the car etc.

check out the suits in Halo2, they have some scuff textures to make the metal of the suit appear more believable and another texture reflecting the environment. You obviously couldn't do this with a static image.

T101
06-10-2005, 08:15 AM
Strictly speaking, you don't need multitexturing for any of that stuff.

You could also do it with multiple render passes.

But multitexturing allows you to do it in fewer passes (sometimes just one), and that means better performance.

Overmind
06-10-2005, 08:30 AM
Of course, but in the context of the original question, you might also ask what the application of multipass algorithms is because you just could pre-blend the vertex colors and textures ;)

Ehsan Kamrani
06-10-2005, 12:51 PM
Thanks a bunch. i'll study the suggested applications and if i have other questions, let you know.
-Ehsan-

Omaha
06-12-2005, 05:04 PM
Question: What are the applications of multitexturing?
Answer: (head shakes, smokes and explodes)

Really too many to list. Light mapping, texture modulation, detail texturing, alpha mapping...