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Author Topic: Building Valid Shaders for just about Anything from Robyn.  (Read 125 times)

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Offline sanbie

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Building Valid Shaders for just about Anything from Robyn.
« on: August 12, 2010, 06:47:53 PM »
Part 01... Introduction

I wasn't sure at first where to put this post (or series of posts), since it kinda fits into several areas, but I thought it made sense to put it with Panthia's elegant GlowMoon tutorial because hers also deals with shaders and the material room, so mine won't feel so lonely.

I'm going to try to make this as "for us Dummies"-friendly as possible, which means, I'll try not to assume *anything*. Much of what will be introduced here is going to be a digestion of what BagginsBill and I discussed in this thread:

You are welcome - indeed, encouraged! - to have a read of that thread. BagginsBill is the recognised expert in things mathematics and materials for Poser: recognised by those-that-know in Poser community at large, but particularly who start to delve into shaders to any degree. I use his contributions as the basis for the information I'm presenting here. I have BagginsBill's permission to directly quote him.

So, what is a shader?

That's a screen capture of a shader. Or Shader Tree. But basically, a shader. This one is for a specific material called Skin, so it's called a Skin Shader.

This is also a shader. Just a very simple shader, true, but never-the-less, a shader.

Still haven't answered the question, have we? So, what is a shader?

A shader is a collection of nodes (those odd little boxes you see in the above pictures) that are all plugged together to define (describe) a material. A material can be anything: glass, water, rock, textile, brussel sprouts or dog poo. Or skin. When you look at a poser object in Flat-lined mode:

you can see the individual polygons (surfaces) of your object. This is what the object actually looks like in a modelling program. Poser does some clever maths to make it all nice and smooth, so when you see it in smooth-shaded mode (Ctrl-8):

you see the object smoothed out. However, it looks like it's made of grey clay. Still can't tell what sort of material it's made of. It's only when you see it in Texture-shaded mode (Ctrl-9)

that Poser gives you a low-resolution preview of the materials on that mesh.

For Poser, a shader is what defines (describes) an object's materials to the renderer.

As you know, for Poser the preferred render engine - what actually takes the picture - is Firefly, although it also comes with the Poser 4 renderer, a Sketch renderer and a preview renderer.

Shaders are set up in the material room (the tab next to the pose room in Poser). If you look in the material room once you have a figure loaded and click on the advanced tab ( don't have much use for the simple tab, since it leaves far too much info under the surface - I wanna *see* it! ), you'll see two drop-down options at the top: Object and Material. If no nodes are in that big area, you probably don't have any object (or material) selected:

Your Object is typically the figure or prop you loaded. The Material Zone is the part of that object that uses a particular type of texture or colour or whatever. On a skirt, for instance, the waist band might have its own material, so the artist can define a colour or texture to it different from the rest of the skirt. On a body, the material zones will be general areas like torso, head, face (separate from head), fingernails, and so forth:

So, for dropdown Material, think Material Zone.

In the main material room work area (in the advanced tab) you will see a minimum of one box with a name on it. Any box in that area would be called a node. The one labelled PoserSurface is actually a super-node: it is the one the renderer gets all material information from when "taking a picture".

So, what does a node do, then? It holds information about the material for a specific material zone or does math or creates a texture, like the Spots node. A material can be as simple as a picture that gets wrapped around the object to make it look like an arm or a leg or an iris or a banana, or it can be as complex as a whole network of nodes doing specialised maths in order to give just the right texture and colour and effect. Like my skin shader, for instance. It defines the texture, tinting, bump... right down to blemishes in the skin:

Most manuals - including the Poser Manual itself - explains in great detail how to achieve the texture map approach to giving your objects a material for the object's surface. Since so much emphasis has been given to this technique - you would think it's the only valid one! - I'm not going to cover that method at all... been done to death, that one. The purpose of this thread is to explain how to achieve that second, more complex objective: creating a network of nodes to give just the right texture and colour and effect.

Offline sanbie

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Re: Building Valid Shaders for just about Anything from Robyn.
« Reply #1 on: August 12, 2010, 06:48:35 PM »
Part Two.

Part Two: Welcome to PoserSurface, the Mother Node (to be edited with images and flesh out, so you might wanna come back to this one)

First, I need to clarify... this is designed, hopefully, to be a true For Dummies thread. I see that at least nine people have read this thread. At this point, I'm a little uncertain if my approach is a bit beyond what folks here are able to get the head around. If it is, do let me know... you can always PM me if you don't want to post in this thread.

Today, we're going to have a look at that PoserSurface node in greater detail. If you'd read that Nodes for Dummies thread, you might have picked up that there's almost like two main groupings in that node. The first group is affected by and takes into account the light(s) in the scene - the second doesn't.

What does this mean?

Allow me to illustrate, but first, let's get some terminology out of the way. As you go down that PoserSurface node (which I'm just going to call PoserSurface from now on for brevity), you see a whole heap of names, starting with Diffuse_Color. Those are the names of the PoserSurface channels. Other nodes can be "plugged" into these channels, which changes the value that that channel passes on to the PoserSurface node, which in turn gets passed on to the renderer (like Firefly), which is PoserSurface's primary purpose: tell the renderer about the material characteristics.

Does that seem pretty clear so far?

It's important to understand that all those boxes called nodes wired together are designed to ultimately do something to (affect) PoserSurface. The information in PoserSurface is what the renderer needs to create the image. So, all roads lead to PoserSurface. And PoserSurface tells the renderer what to do.

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