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Specularity on one part of a texture

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  • replied
    good info fm

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  • replied
    Just a couple of pointers:

    The specular highlight on metallic surfaces tends to be softer (lower power) and exhibits some colour inheritance from the surface itself. In other words, a yellow metal like Gold will generally have yellow highlights. However setting the specular colour to the same value as the diffuse can result in over-saturated hot spots from specular contribution, so often a desaturated and slightly off-hue version of the diffuse can provide better results, though the reverse can sometimes provide a more visually appealing and realistic result (desaturated diffuse, saturated specular).

    The specular highlight on plastics/glass or derivatives is usually tighter (higher power) and does not inherit colour from diffuse.

    Layered materials can exhibit both behaviours - take for example a red metallic car paint with a white light source. The lower layer consists of small metallic flakes mixed in with the paint, which create a broad, soft, red specular highlight, while the clear gloss coat over top will generate a tight white highlight over the top.

    Surfaces such as wood or concrete exhibit specularity more in line with plastics and glass than metals - metals are somewhat a special case.

    Also, the Fresnel effect (Fre-nel, the "s" is silent) can be used to make even more realistic highlights (and reflections if using environment mapped reflections, as a specular highlight is simply a simulation of the reflection of a light source). The Fresnel effect describes how a surface becomes more reflective when the surface normal approaches perpendicularity to the camera, and in the case of transparent materials, more transparent as the surface normal points towards the camera.

    Take for example a glass sphere: Around the edges of the sphere, the surface will be more reflective and less transparent, while in the center it will be more transparent and less reflective. The only time that the Fresnel effect is not clearly apparent is on 100% mirror surfaces, such as chrome (as it's impossible to be >100% reflective).

    Every single object is in some way exhibiting specular reflection. The way we see things is through the reflection of photons. So, technically, every single surface has some form of specularity, being that specularity is simply a simulation of the reflection of a light source. Diffuse surfaces such as paper and non-varnished wood, however, reflect light in a highly scattered manner, resulting in a very soft, very broad specular 'highlight'. Even though we don't usually associate these surfaces as exhibiting specular properties, giving them a very subtle, soft highlight can improve their appearance.

    Hope that's at least a little helpful I know you didn't ask for a rant about the properties of light, and maybe you knew it all already, but incase you didn't I thought it could be of some use. Of course, when talking art, rules are made to be broken!

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  • replied
    You can often also derive specular from the diffuse map since often the brighter parts of the diffuse are usually more specular. This saves on texture samplers. Look at some of the stock materials for examples of this.
    You can also embed specular or opacity into the alpha channel of a texture and import it as DXT5. This reduces the need for two 24-bit textures since the specular doesn't really need RGB storage space.

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  • replied
    Thanks, not sure why i didnt think of that

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  • replied
    Use a specular map - many (if not most) UT materials do this. It's as easy as creating a texture with the specular colour you want for each part and putting it into the specular component. Darker or lighter on the specular texture is a more or less prominent specular, and it can be coloured like any texture too.

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  • started a topic Specularity on one part of a texture

    Specularity on one part of a texture

    I have a large texture which covers a model, and i want only a couple of parts of it to have increased specularity...how do i go about singleing out those parts in the material editor?

    Thx for any help
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