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What exactly is a normal map, a specular map etc

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  • replied
    Whoo, okay. eep breath:

    A normal map is a 2D image used to replace or modify the normals of a 3D surface. A surface's normal is essentially the direction that the surface faces. If you nailed a piece of paper to a wall, then stood directly in-front of that paper, the default 'normal' of that paper would be facing you. By default, the normal shoots out perpendicular to the three edges of the triangle which posses it, but the normal is a value that can be altered. A normal map will replace the surface's normal with an RGB color, the 'R', 'G', and 'B' channels acting not as colors in an image, but as numeric parts of a vector. Essentially, what this does is 'trick' the eye into thinking a single surface is many, thus it adds detail. Even though a normal map may look like a pretty, abstract painting: it is actually raw vectors burned into an image. This sort of map cannot be drawn by hand, it must be rendered via mathematics device (aka computer).

    Specularity is something introduced in Blinn/Phong shading (UT3 uses Phong, the more accurate, but costly of the two). The specular is the exponential increase in intensity of the light as it reaches the dot product of the chosen surface's light vector and the reflection vector. Long story short: it makes things shiny. It is the simulation of a light's reflection. Specular maps are 2D textures used to determine how 'shiny' a surface is, how discriminating the shine (more on that later), and what color that shine should be at any given point. The color values react the way our eyes would interpret them, unlike a normal map: A spot on the specular map that is boldly 'Red' will shine red on the final surface render (unless of course the light incoming has no red value in it, but that is the complicated web of rendering). The specular discrimination (or its more mathematical name Cosine Power) is how bold the specular border is between dark and light. The best example is the difference between stainless steel and polished marble. Both have strong specular, but the steel has a very low specular discrimination, nearly the entire lit surface exhibits some kind of increased 'shine', whereas the marble has a very defined, discernible "hotspot" reflection of the light. These values, too, can be added to a specular map by way of the invisible Alpha channel.

    Bump-maps are the early form of normal mapping, however very few game engines ever used actual bump-mapping. This technique is extremely expensive and is usually reserved for motion-pictures or still-renders. Bump mapping uses a single channel 2D map (or a grayscale image in layman's) to offset the normal direction of a surface. it accomplishes this by calculating the each texel and the eight surrounding it to create a vector, then using that value to offset the original surface normal value.

    I think this is pretty exact. I am writing this from memory, so please don't take this as the 100% correct truth, I am a bit fuzzy on some things.

    Leave a comment:


  • replied
    Originally posted by MrCookie View Post
    Can somebody define these types:

    Normal Map.

    Specular Map.

    Bump Map.

    If there are more than those then please cover them as well.

    Id just like to know what exactly what there are and what they do

    thanks in advance!
    All of them are image types. As your question doesn't directly refer to UE3 material system, I suggest you to google for these therms. There are thousands of sites where these terms are explained in details.

    Try http://www.google.com/search?hl=pl&q...s+a+normal+map

    or http://en.wikipedia.org/wiki/Normal_mapping

    Leave a comment:


  • started a topic What exactly is a normal map, a specular map etc

    What exactly is a normal map, a specular map etc

    Can somebody define these types:

    Normal Map.

    Specular Map.

    Bump Map.

    If there are more than those then please cover them as well.

    Id just like to know what exactly what there are and what they do

    thanks in advance!
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