gloss vs specular maps

[beartraps]

I was wondering what the difference is between these...

[Talon]

Specular controls the brightness of the specular highlight whereas gloss controls how wide the highlight is (i.e. something very glossy has tight, sharp highlights whereas something not glossy has a very wide diffused highlights).

[WildStyle]

Just curious, I know what a specular map looks like. But what would be the typical look of a gloss map? Do you know any referances? Would the gloss map have a same effect as the specular power node in a ut3 material?

[Tiros]

Yep, gloss is the same as the specular power in UT3, only, the RGB-values for your gloss map differ from standard 3d-apps.

So generally, your glossmap would pretty much be a plain colour for each type of material, depending on if it has, and which coating it has etc. Take a look at the gloss-map I used for the leather chair for example: http://i32.tinypic.com/orkksy.jpg (bottom right one)

Now, that one was a bit quick and sloppy though.. I kind of used a general value on all of it and then added in another for the metal and buttons. The wood could proly have used some tweaking aswell, but all in all, that's pretty much what a gloss-map looks like.

To get a hang of what values you should use, if you use max, then create a material and use the gloss slider, compare it to real images of the material you're after, and once you're happy, take that value and multiply it with 2.55 and you got the RGB-value for your map. For Maya, no idea about the values, but I believe they're roughly the same... It's called 'eccentricity' there though.

[glynnsmith]

Not sure if it's been clearly stated here having skimmed the replies, but a gloss map will give you the difference between metal to plastic in your materials - Metal has a low gloss value and plastic can have a mid - high gloss value.

Gloss maps are the reason why Doom 3's materials all looked vaguely midway between metal and plastic, because the engine didn't support gloss maps and the materials were all controlled with a single master value.

[stoopdapoop]

ahhhhh, so like a phong exponent map in source

[Talon]

Yep, phong exponent map (or simply exponent map) are other terms for a gloss map.

[beartraps]

so black will give you an extremely sharp highlight and white will give you a more diffused spread out highlight?

[glynnsmith]

Originally Posted by dieone

so black will give you an extremely sharp highlight and white will give you a more diffused spread out highlight?

You won't want a full black as your darkest gloss colour, as the specular becomes far too wide. I generally use a 10% black (if 100% is white) as my lowest value, to keep on the safe side.

[Talon]

Originally Posted by dieone

so black will give you an extremely sharp highlight and white will give you a more diffused spread out highlight?

Opposite of that, white = more glossy, black = less glossy.

As Glynn mentioned, though, I'd stay away from the pure black and pure white extremes, though, they tend to give very ugly results from gloss as the values are too extreme. I'd maybe stay within the 5% - 95% brightness range.