Leigh texture workshop Diffuse question

[leigh]

Ooops, I am sorry, I did see your question earlier, but I was busy with something and didn't have time to post a reply :blush:

Well, here goes:

In the Leigh workshop, she says that the addition of the diffuse map and the reflexion/spec map should make 100%
And the average diffuse map % of a human skin is around 75%.
So the average spec map % should be 25% Right???

Well, it's actually more to do with reflection than spec mapping. The reflection+diffuse map should equal 100% or thereabouts (sometimes minor tweaking either way is necessary).

But do I have to lower the value of the diffuse map where the spec map is higher?

No, not necessarily. Like I said above, it's more important when dealing with reflection maps, because colour messes with reflections, and therefore needs its diffusion controlled.

If my character is sweating, and I want to higher the value of the spec to 75%, do I have to lower the diffuse map to 25%??(making it very dark)

In this case, rather use a reflection map. But very very subtle. Reflection mapping actually works really nicely with human skin, as long as you keep the values fairly low. They tend to give much nicer highlights than spec mapping.
So in this case, yes lower your diffusion slightly when the reflection map increases for the sweat.

So I will end up with a diffuse map of an average 75%, with darker parts where the spec map is higher, AND darker part on the places like beneith the chin, the side of the nose and close up the eyes???

It depends on your reflection maps :shrug:

On her Orc making of, when making the diffuse texture she says that she only used a plain flat value of 75%.
Why?? would it have been very easy to just use the Spec map and invert it, add the cracks of the bump and use it as the diffuse map???

I didn't bother making a diffuse map for the orc because he had no reflectivity. Setting the amount at 75% worked well, and I liked the way it looked, so I left it at that.

Then on her making of one armure, the thing is in metal with a High value of specular all over, but then again she says she only used a plain 75% value on the diffuse map!!!.. I would have thought the diffuse value would have been very low no?? And again why not just use a copy of the spec map and invert it???

Again, there was no reflection map.

See, I'm totally lost here.

Hmm... did I say in the diffuse tut that diffuse should be used with spec AND reflection? If I did, I better go change that, as it's not really necessary for spec.

In the end, don't panic - do what looks right, and looks cool :)

[leigh]

Righto, I went and checked the diffusion tut, and I know what caused this confusion: when I said reflection/specularity, I said that because some people use reflection maps as their spec maps, and vice versa. I should have made a note of that in the tut, but I have now edited it to just say reflection maps, and not mention spec at all :)

[3dcartoon3d]

Thank you very much Leigh!!

Too much coffee and too much reading yesturday made me lose my sanity a bit:)

Now everything makes sence!!

Take care!

[leigh]

Excellent to hear that you understand it now :D
And yes indeed, too much coffee makes the brain go a bit strange, hehehe.
Have fun texturing! :thumbsup:

[Laa-Yosh]

Pardon me, but I have to disagree with Leigh on the question of diffusion/diffuse channel...

AFAIK she wrote something like it defines the amount of light reflected from the surface. This is, IMHO, a bit strange, as the diffuse color channel is exactly the same, but combined with information about the wavelength (=color) of the light. You can test it by applying your diffusion map as a greyscale mask for your diffuse color. Thus the separate diffusion channel is only there for easier control. Note that many applications have lacked it for years, but it has not affected the ability of their users to create realistic images.

I believe that the diffusion channel's main use is for somewhat procedural textures, mostly facing ratio ramps / camera angle gradients / falloff maps (Maya/LW/Max terminology). Most surfaces tend to change their characteristics depending on the angle of the reflected light; one common example for this is the Fresnel effect on reflections. This basically means that most surfaces get more reflective as the viewing angle increases; thus reflections are stronger on the edges of a sphere than on the front of it.

Some materials change their diffuse color intensity based on the incidence angle, like most cloth. Other materials might even change their color as well.

The idea of muting down the original color of an object so that it does not mess with its reflection is interesting; but it would stop us from getting tinted reflections, wouldn't it?

Other uses for the diffuse channel could be:
- easy adjustment of color textures to avoid washed out areas where the lighting is too strong
- baked ambient occlusion map (we use it for this)
etc.


Please don't forget, I'm not arguing to offend anyone or start a flamewar... peace ;)

[leigh]

AFAIK she wrote something like it defines the amount of light reflected from the surface.

It's the light that is absorbed by the surface, as far as I know :)

Thus the separate diffusion channel is only there for easier control.

Exactly :)

I generally use it for ramps (as you mentioned), as well as instances where the diffusion needs to change without the colour changing (such as when water is spilt into fabric). Most of the time I just use a straight value for it, to prevent oversaturation of the surface.

The best use for it is with reflective surfaces though. Using a diffusion map with a reflective surface improves the reflection a lot :D
(using opposites for each - ie making the ref map and then inverting it for the diff. This lessens that muddy, milky look that reflective surfaces can often get.)

The idea of muting down the original color of an object so that it does not mess with its reflection is interesting; but it would stop us from getting tinted reflections, wouldn't it?

Only if the diffusion was at 0%, I would imagine... It would stand to reason that if you had a percentage of diffusion then you could technically still tint your reflections. I must try that out though.

I must admit though that the diffusion workshop is not well written... :blush: I really must go and rewrite parts of it...

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