Home Technical Talk

Specular level/power vs specular color vs gloss

polycounter lvl 12
Offline / Send Message
ablaine polycounter lvl 12
In what order do most people create these maps? What are each of these used for? I'm familiar with making specular color maps but when it comes to spec power and glossiness I find myself confused. I understand that spec power is used to increase or decrease the intensity of the specular (making the specular more intense for metal than for skin, etc). Is it a greyscale map? What about glossiness? Isn't it used to achieve the same effect?

Thanks in advance. :)

Replies

  • Buzzy
    Spec Power and Glossiness are the same thing. They are greyscale maps that dictate the size of spec highlights (not to be confused with brightness). A higher gloss value (like white) will make the spec high light very small, simulating a very glossy surface. A low value (like dark grey) will make the spec highlight large, simulating a dull surface. Depending on the shader, going to complete black in the gloss map can sometimes cause odd effects.
  • cman2k
    Offline / Send Message
    cman2k polycounter lvl 15
    "Gloss" is commonly referred to as "Exponent" as well. It defines the width of specular highlights, which can be used to fake "hard" or "soft" reflection of light.

    This image from the Valve wiki shows it really well. Specular Strength and Exponent can be used in conjunction to emulate a variety of surface properties. The better you can control these and how they work together, the more convincing and engaging your materials will be.

    Specvsexponentinphong2os.jpg
  • ablaine
    Offline / Send Message
    ablaine polycounter lvl 12
    Cool, I think I understand. That image is very helpful, thanks guys!
  • r_fletch_r
    Offline / Send Message
    r_fletch_r polycounter lvl 9
    One other thing to consider with specular is that the more specular something is the less diffuse it is. So basically if x amount of light hits a surfaces then some is absorbed, some is reflected as the diffuse component and some is reflected as the specular component.
    You never get a surface with 100% diffuse and 100% specular... otherwise the object with actually be self illuminated.

    1 thing about spec which sucks is its just a reflection of the point lights you have in the scene with no response to surrounding surfaces, so essentially you get about the same reflections you would get if you suspended your object in a void with a few point lights floating in it. You get much better results if you fill the reflections in with cubemap reflection which is modulated by your spec and gloss maps.
  • jocose
    Offline / Send Message
    jocose polycounter lvl 11
    Another thing to consider when perusing a particular look is that specular can also be judges or quantified by how much contrast there is between the local color (diffuse) of your object and the highlight itself.

    So if you have a lighter object a brighter spec might be more desirable, and if you have a dark object a duller spec might be more desirable.

    Provided your emphasis is simply on how "shiny" something looks rather than being accurate.

    Its just another way to think about it when your making your maps.

    You can watch a video that goes over this emphasis on contrast here: http://video.answers.com/diffused-and-specular-highlights-148098913
Sign In or Register to comment.