Spec Maps: The Red Headed Step Child
polycounter lvl 14
I wanted to start this thread to learn more about creating better spec maps. Spec maps always seem like they get no love and are just an after thought to most models. I'd like to hear any techniques, facts, links, good examples or anything related to creating great spec maps.
How are you using color to make your spec maps more belivable? What colors work well for creating different materials?
How are you using color to make your spec maps more belivable? What colors work well for creating different materials?
Replies
To create a spec map by hand make sure you have most of your different materials and details in your diffuse on separate layers.
Take those layers desaturate and adjust their values accordingly to represent their reflectivity using levels and different blend modes. Use reference and make sure your materials read well in relation to each other, don't neglect scratches and dirt.
Make sure you test your spec map in your engine or renderer to see if it's reading well then tweak accordingly.
Coloured spec maps
It depends on two things, the engine and the material.
Most materials do not have a coloured specular, it's a lot of metals and iridescent objects that do. So use reference to see what your materials specular looks like under neutral light.
If you are using an offline renderer then greyscale spec maps will do, but because of the additive nature of some game engines specularity you can get "hot" or wrong looking highlights. To counter-act this you can use the opposite colour in your spec map so the highlight is more neutral. A common one is tinting the spec of skin blue.
I've seen a lot of people just keep the same colours of their diffuse but less saturated and more contrast.. and it looks wrong because then things look more metallic.
Some tips
It can help to put AO in your spec map, depending on your engine.
It can look nice to add extra scratches and/or dirt that isn't in your diffuse into your spec so it shows when the light hits it.
Adding more specularity to the edges on mechanical objects can make them stand out more.
Don't just desaturate your diffuse or run it though crazy bump. give it some love
Oh and, a specular map controls how specular (reflective) a surface is, it is NOT a representation of how much light the surface is reflecting under a set lighting condition, some people seem to get this confused and get bad results and ideas.
#1 STUDY, study, study, study, and then study some more, day dream and stare at things, random things, everything! Study material properties and then try to emulate those as best you can.
#2 Work on your diffuse and your specular at the SAME TIME. Too many people think a specular map is something added after the fact, but its very important that your diffuse works well with your spec. If you go about finishing your model, making it look good with just the diffuse map, all you're doing is working against yourself, as you've probabbly added a lot of detail that should have been in the spec in the first place. As far as doing this in practice, i usually get my base details squared off in the diffuse first(defining rust, etc) so the details that need to share the same shapes can be easily copied over, and then move on to unique detailing in both the diffuse and spec.
#3 Not everything needs to have specular reflection. I see this on a LOT of people's work, they'll make a wood crate with a spec map..... Why do you have an old, worn, dry crate that has shine to it? It makes no sense. Again this comes back to #1, but do not be affraid of using very little to no spec on materials that do not have a shine. It's ok to have parts of your spec black because those material's do not shine, its not "wasteful" or any other such sillyness, unless you can easily seperate your textures into different material types(tiling textures sometimes...). One of the most important things in material definition is material contrast, so if you say have a wooden barrel, and it has metal rings around it, the rings should definitely have spec whereas the wood would have little to none, this is what will help make both of those materials read as what they are, instead of looking like they are covered in splooge.
Now its important to note that i am NOT saying wood never has shine to it, certain types of wood that are laqured etc will have a nice shine. In that example, another important thing to note is that the specular is generally very smooth, so things like wood grain, etc may not show up much if at all in your spec, i often see people simply desaturating thier wood diffuse and using it as a spec when trying to represent this type of material.
#4 Experiment! This goes a long with studying, but a huge part of finding out which colors give you various types of effects is simply to experiment, try different things, try things that look absolutely terrible in photoshop, they might work on the model! When creating textures for dynamic materials, what they look like in photoshop is almost completely irrelevant, all that matters is how they work on the model in the renderer/engine you're using.
A quick example is gold or brass, they types of materials can look bery good with a brownish diffuse, and a yellowish spec, a bit more greenish spec and you'll have more of a bronze type look.
http://tech-artists.org/wiki/Portal:Shaders
This is the common problem that I am constantly seeing, and the main reason why I created this thread. Hopefully we can solve some more spec problems.
EQ - Lots of great tips in there...too many to mention.
"A quick example is gold or brass, they types of materials can look bery good with a brownish diffuse, and a yellowish spec, a bit more greenish spec and you'll have more of a bronze type look."
I would really like to hear from others about their expierments with color. What colors seem to work well like: blue/skin green/brown=bronze
After looking through CoD4's characters I noticed that there spec map had a lot of noise. The noise was being use to create the look of skin pores on an arm, for example. I actually like this method better than trying to put the majority of your pore detail in your normal map.
Rob G - Thanks for the link checking it out now,
So imo image examples would go a long way here
Also, when I'm making textures, I use layer masks for pretty much everything - that means I can just copy and paste the mask over to my spec map, and if I change a diffuse layer I can just paste the mask over to my spec again rather than having to copy the whole layer and adjust the colour/contrast/saturation again. Same applies to gloss, reflection and height maps, for stuff like scratches it's great ... if you change the scratches in the diffuse, just copy and paste the layer mask 3 times and all of your other maps match up again and retain their colour/value settings.
some tips:
- as EQ mentioned, work Diffuse & spec simultaneously. I will sometimes take the diffuse to about 60% completion, then start honing in specular stuff. When i go full on in both however, i usually complete stuff quicker, because there is less "noodlin" around what you want your stuff to look like, and you cna get it right the first time.
- Similar to that, be sure that you take into consideration details from your diffuse in your specular. Try to come up with cool, different things you could do ie: You have a nice grungy black bit on your mesh... but what if you flip your brain, and think of *that* as the metal, and the rest as oxidation/grime buildup? Make the grime in your spec light gray/white (ie invert values), and blamo! cool lookin surface.
- noise in your spec is good, but selectively, or with moderation! If there is a large surface of metal, and your overlay textures are pretty noisy when you increase the contrast, put a subtle blur in that area. You can use two layers of your grunge ehre as well, and pull in some blurry spots & some sharp spots. Noise in your diffuse w/ blur doesnt look too hot, but noise w/ some subtlety is nice.
- it may be obvious, but use specular to define your materials. Don't be afraid as EQ said to flatten something out, or use a very dark value. Your specular will have as big an impact on the mesh as your diffuse does for color.
- try to get some contrast in your specular, will help accent your diffuse and normal.
- Just as you play your specular to your diffuse, you also must have the normal map support the specular. If you dont, there is a chance that the cool detail you put in the area & speced out/in will be lost or not as punchy w/o a subtle bump. Adding a subtle bump will accent your spec further, and possibly allowyou to tone it down and refine it more.
- Black is GOOD - use it wisely!
few more:
- MIND YOUR EDGES!!! You dont want to go full out overboard and make everything white, but you can help accent the shape of the mesh&normal map by punching up the edges. This can further the illusion the normal maps create, and really help sell the mesh. Conversely; if you have things sitting "on top" of other things, punch the edges between that surface and the other w/ black edges. It will help pull the two apart, and make the rest of the spec appear more cohesive.