Lookin' for some relatively inexpensive (...free?) software that will take a texture and generate bumpmaps, height maps, etc. (Btw, are bump maps/light maps/alpha maps all the same thing?)
And...can all that be done in Photoshop?
You can do that with an art program like photoshop but it won't give a true bump or normal map. It will just basically change it to a 2 color image and the light or dark places on the image can be used for height. This may or may not be true to the image. To do a true normal map, you need to do a light bake on the model. One program that does this is xNormal. You can also do it with a modeling package like Blender.
Bump maps are maps that are used for defining normals in the 3d engine, so they give the illusion of depth.
Light maps give the illusion of shadows, but they aren't real time.
Alpha maps are used for transparency.
Thanks fireside, great stuff. That's really helpful.
I wasn't aware that light maps aren't real time. What's the purpose of them then, if one can simply do said shading in the original texture art?
Light maps are a lot easier on the cpu than doing real time lighting. I know Unity still uses them. If you are developing for lower end hardware, they are helpful.
It's useful to separate light maps from the texture maps because then you can re-use a texture map many places and apply different lighting on top of that. If you baked the lighting into the texture, the lighting would need to be the same everywhere that texture was used. Lightmaps are typically uniquely UV-unwrapped, so every surface has its own section of lightmap that's not used anywhere else. Also, the lightmaps are lower resolution to save memory and performance, since lighting is often smooth and does not require sharp details, especially indirect lighting. It's not uncommon these days to use lightmaps (or some other kind of pre-baked representation) for indirect lighting, and use real-time methods for direct light.
What's the difference between "baking the lighting into the texture" and, how to put it, "regular" light mapping? I know from studying the Beast (or whatever it's called) baking system in Unity that light mapping is something that's done during development, not real time, but I don't quite have a firm grasp of what light mapping really is. Bump maps and alpha maps are quite obvious, but light mapping is still something I'm getting a definitive grip on.
By "baking the lighting into the texture" I meant what (I think) you said about "do[ing] said shading in the original texture art". That is, applying the lighting/shading to the material textures as a precomputation, so that at runtime there is no separate lightmap and material color map, just one texture with everything already "baked" into it.
With light mapping, typically there are two separate texture layers - the material texture, and the lighting texture. They're composited in real-time even though the lightmaps are precomputed and don't actually change at runtime. That's what I was describing in my previous post.
Yeah, what the beast does, in Unity, is create a huge light map of the whole scene. It's probably not a texture, just pre-computation like Reedbeta said. In modeling software, it's done on a specific model and added to the color texture. You can also make a black and white texture for light for the model and some engines can use it as a separate texture and add them together. That's not done as much, I don't think, as it used to be because it's better to do the whole scene. Some of it might be done for high/low poly models, where the light and normals are baked on a high poly model and then put on a low poly model to give it the illusion of more detail. I know that's done for normal maps because you can make a low poly model appear to have much more detail with a high poly normal map, so you basically make two models and bake the normal map on the high poly one. That's not that hard because you just stop when you are building the low poly model and save it, and then start adding detail, sometimes in a different type of modeler. Then you use that map on the low poly model you saved. A normal map really isn't much different than a light map. It just darkens the low areas but it uses diffuse light, so it's not coming from a certain direction, or something like diffuse light anyway, it might be using multiple directions or something or not even using light, but the low areas end up being darker.
Normal maps don't store lighting; they store information about the detailed shape of the surface so that arbitrary lighting can be applied without changing the texture. They're mainly used for dynamic lighting; the shader will use the normal map data to calculate better lighting than it could without the normal map, and the lights can move around and change arbitrarily at runtime. Normal maps can also help with increasing detail in static lighting. HL2 had a neat way of baking three different lightmaps that would capture the lighting from three directions relative to a surface, then use the normal map to blend those three together per-pixel. It looks a lot nicer than standard lightmaps.
Oh. I guess because it was being done in Blender, I thought it had something to do with lighting. I know the normals on the model are just little direction lines sticking out of the model, but when you do the texture, then it looks like a 2 color type texture, which is what Unity asks for. It's the same size as the color texture and gets applied in the same way. I just do simple models so the most I do is use a texture with an included normal map or make one from the texture so the model looks like it has a little depth, otherwise it will just look flat. I've seen the tutorials for using a high poly model and baking the normal map and then using it on a low poly.
Just remember to wear oven mitts when you're baking textures
You can also use tools like Gimp to produce normal maps. Normal maps are not created from just multi-resolution models, but also from random images to add deformities such as cracks, scratches, bumps. In some cases like with relief mapping (parallax bump mapping), brick textures can appear extruded while observing at certain angles. None of these situation calls for an original high poly model. My TexGen tool can procedurally generate normal maps if that interests you. There use to be another good tool called MaPZone (by Allegorithmic), but it doesn't look active anymore. At least not the free edition. He's gone pro now. There's also Genetica, which has been around a bit longer. Blender can do these as well if you work with its node editor. If you learn python, you could even write your own algorithms.
For lightmaps, stick with a pro modeling toolkit. Ideally, use a real level editor created by game devs (such as Havok) since they simplify the matter for you. Blender can do this as well, but it's a lot of manual labour. When Blender renders an image, by default it renders the scene to a new image. You can tell the renderer to only render lights and shadows (or ambient occlusion) and specifically to a texture (one that is already assigned to an object). However you need to save that file afterwards and do this for every model. Best to write a python script and go watch a movie while it bakes.