First, a caveat. What I am introducing here in this initial post of the Nodes for Dummies thread is not gospel: it is a synopsis - a digestion, if you will - of my understanding of some of the behaviour of Poser material room nodes based on a series of discussions with CobaltDream, who has been instrumental in clearing up a number of burning questions that prevented my understanding much of what was being discussed on the "VSS Skin Test - Opinions" thread on this forum. Since that thread has so many sub-threads that it has become a bit unwieldy, I've decided to start this separate thread so that Those-That-Know can continue their discussions on VSS unmolested. VSS is Versatile Shader System, a Poser material-room tool developed by Bagginsbill to manage material shaders - node sets - across the range of an object's materials. It's a rules-based system, and really quite clever, allowing you to manage quite complex objects with hundreds of materials.

I'll start with a few definitions.
NODES: Poser has several "rooms", one of which is the material room. In the advanced tab area, one can do clever things with object material surfaces using little boxes called nodes, each of which have a special purpose. For the material itself there is always at least on "mother" node called PoserSurface which has a column of boxes and what look like little plug-in points: these are called channels.
This PoserSurface nodes (or node group) has been discussed at length in other places, so we're not going to touch on it here for the time being.
COLOURMAP: In deference to Bagginsbill's preferences, I'm going to refer to the image and the node that stores it as "colourMap", which sets free the word "texture" for other meanings. To create one of these:
New node >
2D Textures >
image_map
...and then in the Image_source box, click on it and with Texture Manager, click on browse and navigate to the image associated with that material. This is the most common use of the material room and if you look up "nodes" in Poser manuals and such, invariably this is what will be thoroughly explained, because this is what is best understood. Nodes as such will be glossed over, and that is the purpose of our discussion her: to promote a better understanding of how that all really works.

What really got me started wanting to learn more about nodes and their behaviour was a desire to do make-up for my characters not using "painted" colourMaps - painting make-up colours on the base colourMap of the face. In the above-mentioned thread, Bill kinda got me started doing make-up using masks and the Blender node in his PR3 skin shader, an elaborate 55+ node skin node set. I quickly found myself becalmed - no wind for my sails - as I had no idea what most of the nodes were doing, a knowledge essential to being able to manipulate them. It was suggested that I do some experiments which I have documented here, here and here.

As you read these pages you can easily discern that I was floundering. I was rowing madly around but with no idea in which direction I was going. I had no point of reference.

At this point, CobaltDream came to the rescue. I feel an intense debt of gratitude to her for shedding light on what those on that thread pretty much held as common knowledge, but which I for some reason was failing to grasp. That gratitude has resulted in an effort to share this knowledge with you in such a way that it is plainly accessible to any and all who really wish to know and to hopefully stimulate some discussion and perhaps even some experiments that will help clarify to our minds what nodes do what and when we'd want to be using them.

To me, colour is just colour. When I refer to colour, I generally think of the colour of an object. An essential part of colour is light: without light there is no colour. In Poser, colours are a combination of three basic colours: red, green and blue. Most paint and image programs such as Photoshop, PSP and the GIMP use this same colour combination thingie as well. The colour standard that we subscribe to - as in, most commonly use - for our monitors and internet and images and all that is called sRGB, thoroughly described here.

So, colour is just that: colour. An image (picture of something) is a combination of a whole bunch of different colours one pixel in size. That's how I think of colours: this way of thinking created one of the biggest obstacles to understanding some of the nodes like math nodes can change a colour.

This next bit is key to understanding nodes that use maths to change colour, so pay close attention.

Colours can be represented as numbers. There are a fair few ways to use numbers to represent colours. This is nothing new to anyone, but I'm mentioning it for the sake of completeness. In Poser we see two numbering systems in action: in nodes, the range a colour can go to is from 0 to 1, 0 being totally black or absence of colour, and 1 being white. Another numbering system goes from 0 to 255, with 255 being all white. You'll see this system when you use the Microsoft colour picker:

Since Poser nodes don't do maths in that 256-base system, the first thing we do with colours represented in the 256-based system is convert them to the decimal system... that is: that numbering system that goes from 0 to 1 I mentioned earlier. The conversion is quite simple: one divides each colour (Red, Green and Blue) value by 255 to get the decimal value.
For instance, for the red colour you see in the image above, you would convert Red, which is 255, to the decimal value by dividing it by 255:
255/255 = 1
So, Red is 1
0/255 = 0, so Green and Blue would both be 0. So, for Poser, the RGB value of 255,0,0 is 1,0,0.

This way, Poser can do maths on this decimal value.

Make sense so far?

For the most part, though, we really don't have to worry about doing any conversions, since Poser handles those conversion maths internally. However, it is important to understand how the decimal numbering system works, since we're planning on changing or affecting colours by doing maths. For instance, when we do maths on a colour, we do it on all three (RGB) simultaneously.

Let's test all this out. Let's say we've got a the colour green, which is 0, 255, 0 in the Microsoft colour picker, or 0, 1, 0 in Poser's decimal system. Let's add Red to it, which is 255, 0, 0 or 1, 0, 0.
    1, 0, 0    or   255,     0, 0
+  0, 1, 0   or        0, 255, 0

---

   1, 1, 0   or   255, 255, 0
  
or yellow.
So, one can do maths on colours and get meaningful results. We haven't done anything earth-shattering at this point, but we've established a good starting point, I'd say.

Comments by Those-Who-Know are always welcome and indeed, encouraged!

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks