Color Map And Diffuse Map

#1

Can anyone help me out to differentiate between Color Map & Diffuse Map.
What is Color Map & Diffuse Map.
if possible then plz explain with some example.

#2

It depends which software you’re using. In a lot of software, a diffuse and color map are the exact same thing. What 3d package and renderer are you asking about specifically?

  • Neil
#3

I am asking in Maya.

#4

They’re the same thing mostly. The diffuse map is a greyscale mapping of diffuse strength, while the colour map is r,g,b. The two are multiplied together in the shader. To see what it’s doing take your diffuse map and your colour map and layer one over the other with ‘mulitply’ blending mode in photoshop.

#5

‘…the same thing’…? Ah, no. (I know you said ‘mostly’) Be careful when saying it like that, some people will take you at your word!

Your diffuse map controls how much of the light is scattered/reflected back off of the surface. You can start with a highly desaturated color map, but you’ll be pushing a fair bit of your D map lighter and possibly making adjustments to your color map at the same time (go easy there… I mean, when you crate your color map, you pretty much nail the color that you want, so you don’t want to go tweaking it a lot) .

You’ve got to understand diffusion to get the most out of your texturing. I think it’s a shame that most people go with a color/spec/bump approach, and so it’s really cool that you’re asking about it.

#6

Sadly, in some software they are actually the same thing. Max’s “Diffuse Map” in the Standard Material is exactly the same as a “Color Map” in other software. That’s one of the problems with having a really young industry like this, there’s no real standards and so a lot of the same concepts get named different things, and a lot of different concepts get named the same.

  • Neil
#7

Yeah, I know it is in Max, and it’s wrong. :slight_smile: It’s nuts, but that’s a good cautionary tale.

As for Maya, or any other diffuse, another thought after I posted: be sure that if you opt not to use a map, that you at least do not use full intensity or value in your diffuse slot. As an automatic, depending on software, I knock the value to 85 or 90% as part of material or shader set-up, then tweak that value later again.

#8

Yup, it is wrong, but alas, that’s the way it is, and so can’t be ignored. Personally I prefer the Color Map and kd combination you get in prman and brazil, but I’m sure everyone has their own preference for names.

  • Neil
#9

No, it’s not wrong, it’s just slightly confusing naming applied to the controls that leads people to make wild assumptions based on nothing more than guesswork and a vague, hand-waving understanding of how these things work.

Colour (or diffuse) and diffuse strength (or Kd, or diffuse gain, or whatever else you want to call it), map exactly the same values. They are multiplied together with the integral of the light arriving from all directions over the hemisphere to give you the diffuse result. The only difference is one gives you separate controls for r,g,b and the other gives you an overall scaling factor. This is true for all shaders I have ever seen.

I really don’t know where this idea that the diffuse parameter is doing something magical came from, but it seems annoyingly persistent (incidentally, diffusion is a completely unrelated process).

#10

Remove the word “slightly” and I’ll agree with you. I suppose the word “wrong” should never be used, just like one should never say “never” :).

But this naming oddity does lead to a lot of confusion. Which is why I would love to see the nomenclature unified across all the 3d apps out there. Unfortunately, I just don’t see that happening since most named things also affects the way scripts and plugins interact with the systems, and so they can’t be changed due to backwards compatibility reasons.

  • Neil
#11

The trouble really I think is that in order to be precise about it you need to use quite scientific nomenclature. I’ve to’ed and fro’ed somewhat with our proprietary shaders beweetn being overly scientific and overly ‘TD friendly’. Each way of naming comes with its own set of confusions. It’s a bit of a losing battle I think :\

#12

For me precision is not as important as consistency. Call it “ham sandwich” if you want, as long as every app calls it “ham sandwich” and every person I talk to knows what I’m referring to when I say “ham sandwich”. Then again, you’re a hardcore programmer and I’m an TD/Artist so we probably have somewhat different views on the subject :slight_smile:

  • Neil
#13

Well I tend to do both but I guess since I write the stuff as well as use it your point stands :slight_smile: I’ve bollocked on in other threads about misuse of even the simplest terms like reflection and specular. It might seem pedantic, but when you’re dealing with complicated effects it quickly becomes impossible to talk about what you’re doing without being fairly precise about it.

When we can’t even all agree on what a strength/gain/Kd parameter should be named I guess we have to give up and just learn to live with what we have. And this is before we even start thinking about what we name passes we give to comp! :slight_smile:

#14

Some artists use them differently. For the color map, they paint the main colors of the surface. For the diffuse, they paint a layer of fake self-shadowing or create something that looks like a baked occlusion map, adding a cheated type of shading to bring out details on the surface. If you’re working this way sometimes you want the color map to tile and repeat across the surface, but the diffuse map to only cover the surface once so that each crack and corner can be individually darkened, so it’s handy to have them as separate maps.

In Maya, using a PhongE shader, as long as the whiteness is less than 1, the color will also influence the specular highlight color, whereas the diffuse will have no effect on the specular highlights colors. Also, in Maya, once your color is mapped you can’t slide the color brighter or darker in the material to brighten or darken it anymore, so having a second top-level control in the material is handy for quick tweaks and over-rides to the brightness, even if they are just multiplied together.

-jeremy

#15

Good point - we tend to add diffuse maps at the end of the lookdev process to fix up assets where some details are too small to be efficiently shadowed properly by maps.

#16

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