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IMVU Studio - specular maps

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Offline kat

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With recent news of IMVU Studio in the works and its release later this year, Creators may have the ability to include SPECULAR maps. For those that don't know what they are, the following is a basic breakdown (Blender is show below for convenience and illustrative purposes, images will be updated once IMVU Studio is available).

IMVU Studio
IMVU Studio with various texture slots available for materials (the above is a mockup and may differ from the final version) - specular maps would be placed in the "Shininess" slot. [image courtesy IMVU].

What is a Specular Map

Generally speaking a specular map is a bitmap image used to create the effect of shiny or glossy surfaces. Its generally an 8 bit greyscale image, but can also be a 24 bit RGB that's desaturated to grey, that occupies a specific 'layer' of a material that's assigned to an object, often as a compliment to other layers performing different jobs - for IMVU this would mean being an additional texture slot for for standard matterials in the editor.

Design note: the advantage of 24 bit RGB over 8 bit greyscale is in the amount of tonal (colour) complexity the first provides compared to the latter.

The difference between specular and non-specular avatar
Specular map make objects look shiny or flat (shown in Blender by way of example) - highlights or shiny areas appear that way in relation (perpendicular) to light sources (not necessarily the viewers point of view).

How do specular maps work

In a nutshell, specular maps work by interpreting tonal values, typically black through grey to white, as representing the degree to which a material should appear, in part or whole, glossy or shiny. In most instances 0% no shine - 100% full shine, or;

Black = 0% (shine).
Grey = variable shine
White = 100% (matt).

Design note: specular maps can be coloured but will generally be simple greyscale images to limit the degree to which the tint may interfere with an objects final appearance.

Different types of specular map
Specular maps are generally just greyscale images (right - show as black and white for simplicity) but can be selectively coloured (left, middle) depending on the desired visual effect - the version to the right would produce a strong green tinted highlight with a matt body, the version in the middle a flesh tone highlighted body to match the default avatar (caucasian in this instance) with a PVC like MCG; the version on the right would be similar to the middle absent colour tinting.

How are specular maps made

Generally speaking, sized to match other textures in a material, they can be as simple as a single uniform greyscale value (black, white or grey), or for more complex specular effects, features can be painted, or areas marked out, using different tones/colours to represent varying degree of effect influence, grey circles for chain-mail for example, larger white areas to give the impression of PVC underwear (see below), or very dark grey (80% » 95% black) for a satin or sheen finishes.

Design note: unlike normal textures, 'highlights', those areas normally used to indicate lighter tones when looking at something - the thighs of the avatar for example - are not included except to indicate wear or a variation of the effect; they're not painted the same way as diffuse images where highlights are concerned.

Specular PVC & flat skin vs all shiny skin
Because white or lighter colours result in surfaces being significantly shiny, anything that needs to be matt is typically black (100% black) or near-black (95%+ black), anything else will result in a noticeable sheen.

The avatars skin is shown without highlights whereas the MCG area has specular to make it look like PVC by varying the black/grey/white tone associated with different regions of the image.

Resources

Download example files (*.psd & *.tga images).