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).
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.
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.
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.