Color and Specular Maps

Saidin311

I've done a quick search around here/net and I can't find too much as far as an explanation of what a specular color map is, or how to go about creating one and what colors to use.

I'm used to using specular as a greyscale type map.

Can anyone point me to a good resource for specular maps specifically color ones? I'm trying to figure out what they do exactly and how to utilize them to my advantage. Specifically I'm texturing a few lights for a scene I'm working on and I think that I might need some color specularity?

Thanks in advance for helping a noob!

Mark Dygert

Ironic, that the post right above this one (as long as it stays at the top of the forum, which won't be long) deals with just this question.

http://boards.polycount.net/showflat.php?Cat=0&Number=81058&an=0&page=0#Post81058

Specularity is the light shining off an object. It's a faked reflection. With a black and white spec map you always get a white highlight. Coloring your spec map gives this faked reflection different colors besides white. You'll get widely different results and its best to experiment with it on different materials to get the results you want. The best tutorial about colored specularity is the one you'll write

culturedbum

Hey Saidin, Not sure if you already found a source for this but I thought Id give it a try.
-A color specular map(this is my definition so someone please correct me if I'm wrong)is a map used to allow the light on a surface to bounce off and create an illusion of specularity.
A classic example is the light that bounces off of polished metal.
-the more complex (not so much complex but confusing) part begins when the light that bounces off cant just be white as it looks wrong, The way I like to think of it is just like the sky when it bounces off of your skin to give it a shade of blue, or any other light that affects the color of a surface.
-it makes the surface have a broader range of colors making it more interesting to look at and more complex.

- the choice of color comes directly from the surface you're working with, referencing the sky again I like to make my specular colors for skin be a shade of blue.

Looks at this guys work for inspiration and to see what I'm talking about. David Pain
Look at the way he made his specular and the way it reflects off of the characters skin....

Anyways I hope that helps.

(and Vig posted just as I was typing.lol)

Saidin311

Thanks for the explanation guys! I looked at that thread, in fact I've been using that thread for a reference for the last couple of things I've made, they talk about application of specular and normals and how to generate them, but not really much of what the colored map does.

Again, thanks for the direct and really clear explanation! (if any admins are reading they might want to merge this in with that thread above this, appologies for the semi-repeat post).

Ryan Clark

Hi Saidin311,

Here are a couple of examples to illustrate the role of a colored specmap.

First, look at these Apples. Notice the apples are red, but their specular highlights are white. You might create a similar effect by using a white specmap.



Next, look at this Christmas ornament. Notice the ornament is red, and its specular highlights are also red. You might achieve a similar effect by using a red specmap.



As a rule, wet and waxy objects have white highlights, while metallic objects have colored highlights. Of course, most materials are going to be more complicated than these... but I hope they help to convey the general idea.

cheers,

-Ryan Clark

Saidin311

They do for sure, but a follow up would be couldn't I just use a red light on that Christmas ball to get the red glow? (assuming I'm using a black/white spec).

edit: Although to answer my own question, I guess if I used a red light I'd have red on the background layout too (red indirect light bouncing off the ball too). Although there is some coming off the light in this particular example.

If I took those apples and placed them under a red light and used natural red light instead of a flash bulb then they would also have red highlights?

I mean I understand a little theory behind the light and such. But as far as replicating it on the computer. I've experimented with some specular and I'm not quite getting the result I thought I would. Do the colors on a color specular map need to be vivid? IE Red for a red highlihgt (as opposed to some sort of faded red shade).

Ryan Clark

Yes, an apple under red light would look similar to a metallic sphere under white light. But if you want both in the same scene, you'll need colored specmaps.

BTW, on second thought you might achieve a really white highlight on the apple by using an aqua specmap. Because specmaps are additive, and red + aqua = white.

That's the reason why people recommend a blueish specmap for human skin. Because yellowish skin + blueish specmap = white highlight. Which is about right for the oil and perspiration on human skin.

Incomitatum

In seeing what it should look like, which of the Photoshop Layer Styles mimic the additive process?

Ryan Clark

(edit)- As kind people have pointed out, "Linear Dodge" is Photoshop's mode for additive blending. You can use that to see what color your specmap will produce when added to your diffuse map.

To calculate an additive blend yourself, just add the components of two colors. Thus Red(255,0,0) plus Green(0,255,0) equals Yellow(255,255,0).

You can see this in life by shining colored lights on a white surface, and causing them to overlap each other.



Wikipedia has a short article on additive blending here: http://en.wikipedia.org/wiki/Additive_color

Eric Chadwick

Linear Dodge is Photoshop's additive, but only added since version 7.

Screen is basically inverse-multiply.

doc rob

Ryan, I thought that "Linear Dodge" was equivalent to Add?

Ryan Clark

Sweet!

Disregard that post, then. My information about Photoshop was out-of-date!

Slum

Adobe really should change the names of their blend modes... After Effects uses proper names.. yay for inconsistency

Ryan Clark

I wish Photoshop had a blend equation editor, or some facility for creating new blend modes.

They provide a good plugin interface for filters, but the ability to add new blend modes would be REALLY powerful.

TheSplash

Hello,

Are these the only reasons you would use a specular colour map?

>To simulate metallic or iridescent materials.
>To counter-act the additive nature of speculars.

Mark Dygert

> To fake/bake a world reflection, blue sky on the parts that point at it. Brown/black for the pieces that face the ground. Works great when you bake a gradient over the top of your model.
> To fake/bake sub surface scattering, to a minor degree since the materials color could effect its spec depending on what type of material it is.

And last but certainly not least
> To fake/bake material bounce light color, effecting surrounding objects. Similar to ambient occlusion but instead of shadows you paint the bleeding colors from one object into the spec of the other. A blue cube will reflect blue light on a white object, if those objects are never going to move, you can fake/bake the spec color and not have to deal with long render times trying to get color bleeding/bouncing.

Saidin311

So one last followup here. Is there a way to tell in photoshop what my specular is going to look like on my model?

I know we're talking about using linear dodge and thats PS equiv to additive layering and such, but how do I use that knowledge to pick the right colours for my map. I've seen speculars look like what I would expect them to look like (highlights) but I've also seen them with some crazy colours that seem to make sense when the render comes out. (say using a blue map to light skin).

I understand the colour theory, and highlighting. I paint Warhammer models as a hobby and I've been able to translate some of that knowledge to texturing and creating these maps, but I'm just looking for a way to preview or predict whats going to happen without trial and error.

Joao Sapiro

the best way to predict is honestly to view in your 3d application , because lots of engines interpret specular maps differently, also depends on shaders etc, what you texture for 3ds max might be different for uengine etc , depends alot man.