Class is in session, Im taking my seat now.

present :)

Sure would be nice.

Un coup de dés jamais n'abolira le hazard
S Mallarmé

We're talking about P5 material nodes, I take it? Basically a node is one point in a hierarchical tree of information that all comes together to make a material. A node can be the originator of information or it can be a filter, modifying information that comes into it before passing that information on to the next node. Eventually the information gets to the root node, which tells the material how it's supposed to look on the model. The root node is very similar in function to the Poser 4 materials editor. There are a lot of different types of nodes and they all do different things. All nodes except the root node have one place to output information. Many nodes have one or more places where they can take information input. Some have none. Most nodes have several parameters which control how information is produced or filtered by them.

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Here's a screenshot of a refractive water material built up out of nodes

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And here's what it looks like rendered. This water material is still a work in progress. I was putting together a refractive materials pack for freestuff, but I had to put it aside for a while to do other things.

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taking my seat and late as usual. dave

OK, let's have a look at what's going on with the nodes. For a start, I'm trying to duplicate the look of clear clean water in a bathtub, so I'm following the physical characteristics that sort of water has. Water refracts light - ie light passes through the surface but changes the direction it's going in, which is to say the light gets "bent" at the surface of the water. Refraction requires raytracing, so I've turned on raytracing in the render options. When light strikes real water, some of the light is refracted and some of the light is reflected. After this process, the total amount of light should be exactly the same, so the refraction value and the reflection value in the root node have to add up to 1. You'll notice I have a reflection value of 0.4, meaning that 40% of light is reflected from the surface, and a refraction value of 0.6 meaning that the remaining 60% of light passes through the surface and gets bent. But how much does it bend? In physics we measure this with a refractive index. The refractive index of water is 1.3333 (roughly). To control the light bending I have created a raytrace refract node and set it's refractive index to 1.3333. The information created in the refract node is output to the refraction colour of the root node. I have left the base refraction colour in the root node set to white, because I want crystal clear water, not water with blue food colouring in it for example, which I would mimic by setting the base refraction colour to blue. Notice there is a background colour in the refract node itself which I HAVE coloured blue. This is the colour that will be used if Poser can't figure out what would actually be seen through the surface of the water at that point - if there were only empty grey space behind the water for example. That's taken care of the 60% refraction, but what about the reflection? We need a raytrace reflect node to make sure we're getting true reflections of the objects around the water. I've created one and plugged it into the reflection colour. Again the background parameter tells poser what to show if it winds up reflecting empty space or doesn't have enough raytrace bounces to get to the origin of the reflected light. Since there's a lot of grey space facing the water from behind the camera, I need to be a bit more concerned about what gets shown this time. The three nodes supplying information to the background parameter of the reflect node are just the same three nodes that make up the tiled surface of the walls and floor. I've effectively told Poser that if it doesn't know what to reflect, it should reflect my bathroom tiles by default. My water object is actually just a flat square prop from the prop library. I want a rippled surface, not a mirror smooth flat one. To get the ripples, I've set up some displacement. I've set the root node's displacement to 1 and I'm driving it with an fBm fractal node. That means that wherever the fBm is black the displacement will be zero, but wherever the fBm is white the displacement will be 1. In between shades give in between displacements. There are lots of parameters to play with in the fBm. I just mucked about with them until I had something that looked a bit like water ripples. Finally, water has small, bright, shiny highlights. I can't trust the default Poser highlighting to give me that, so I've set the normal specular colour to black and value to zero. Then I've set up an alternate specular setting with a phong shading node. This gives me a bit more control over how the highlights will look. I can use the parameters of the node to make the highlights small but bright. There are other ways you could approach this problem but the key points here are that if you want realisitic water you need a reflect and a refract node, your reflective and refractive values must add up to one and you must have the refraction index in the refract node set to 1.3333 or thereabouts.

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Here's another example of what you can do with nodes. There is only one polygon in this picture. It's a big flat square being used as the ground. I'm trying to get the look of a plowed field in a strange alien environment. There are two materials here - one for the background sky and one for the ground.

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Here's the material for the ground. You can see it's quite complicated. I started with one of the materials supplied with P5 and then modified it to meet my requirements. The most important thing for me was to get the ploughed furrows with displacement. After that I just messed around until I had the sort of earthy look I wanted with some strange purple highlights at the bottoms of the furrows.

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....and here's the material for the sky. This material is applied to the default "background", not to any model or object. There are only four nodes here (other than the root node), so it's a bit easier to see what's happening. I wanted a cloudy sky so I started out with the clouds node. You can see how I've set the parameters to give me the colours and cloud density I want. But I don't want the clouds to be evenly lit like that. I want the sky to be dark near the horizon and light near the zenith. How do I do that? Well if you've used Photoshop then you're probably familiar with the concept of multiplying colours. When you multiply black with any other colour you get black. When you multiply white with any other colour, you get the colour unchanged. To get the look I wanted I needed something I could multiply with my clouds node. It needed to be a smooth gradient from black at the bottom to white at the top. I can get that easily by using a v texture coord node. This is like the v in uv mapping. It runs from zero at the bottom of a texture mapping to 1 at the top and the visual representation of that is black at the bottom ranging to white at the top - just what I want. Almost. I really need the centre of the map to be closer to black, so what I've done is filtered that v node through a math node set to the "power" function. For each point in the v node map, I'm squaring the value (where black is zero and white is one). When you square fractions, they get smaller, so I'm making the whole map darker but the effect is much more pronounced toward the bottom. Now that I have what I want showing up in the math node, I just need to multiply it with my original clouds texture. I plug both of them into the inputs of a colour math node set to multiply. Now I have a nice cloudy sky texture that fades to black as you go down and is looking pretty dark at about the right place for my horizon. That's exaclty what I want, so I just plug it into the root node in the colour channel. Done. The key thing when working with nodes is to experiment lots. There are lots of different node types and they all do differnt things. To use them effectively, you need to get to know every one so you can think about how to combine them creatively to get the effect you want. I'm still a long way from feeling like I know all there is to know about this tool. I can do some great stuff with it but there is so much more left for me to discover. It's very cool.

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Just for laughs, here's one last example of the refraction node being used. This time I'm immitating glass. The principles behind this one are exactly the same as the water material I showed above. The key differences are that this time I don't need any displacement and the refractive index has to be the right one for glass instead of water.

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Nodes, refractions, deep texture editors, raytracing, caustics, specular, diffuse, materials, mesh... who comes up with these names for objects that sometimes look or do anything close to what they're named?!? Can't anyone just name things in a nice simple way anymore?

Notice how the tiles behind the glass are magnified, but if you look closely you can also see the reflections of the room on both the front and back surfaces of the glass. Here's a quick screenshot of the material nodes.

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Ajax - thanks so much for the great information. Your presentation is excellent and a greatly appreciated departure from the usual kindergarten classes ;-)

Is it possible to put a chart or preset pack together that has setups like water, glass refractive transparent effects?

You built the water all out of nodes? Is the water a polygonmesh shaped like water or is it a flat plane? And the white pattern in your water testure is that something you made in a paint program or all by nodes?

Ok I got it it's a flat plane, wow that looks like a water surface model!

Thanks Ajax. Brilliant.

Un coup de dés jamais n'abolira le hazard
S Mallarmé

You're welcome, people. Glad I could help. Crescent is going to repost this info as a tute over at www.fallencity.net in a day or two and a download package with all of the materials discussed here will be included. Keep your eye out for it so you can get the download. Then you can do some hands-on playing with the materials. Mesh_Magic, The water model is just the standard Poser one-sided square primitive prop - just a single polygon. There are only three things done in a paint program that show up in the examples I've given. Those are the two different tiles that go together to make the bathroom tile surface and the base displacement map that I've used to create ridges on the alien field furrows.

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Ajax, You are brilliant. I have learnt so much just simply from reading your clear and concise tutorial - I haven't started even experimenting yet... regards, Andrew

Attached Link: http://fallencity.net/tut-p5/ajax-nodes101-1.php

Crescent is a little backlogged, but finally got everything up, including the sample nodes that Ajax listed above. Thanks again, Ajax, for allowing me to post this at my site!

Cheers!

(1 overdue item done, way too many to go ....) ;-)