I learned everything I know about Poser from tutorials. I never picked up a mentor or hit up artists for info, I just put my head down and read everything on the net about Poser. Now don't get me wrong, I have no problem sharing my secrets, and I certainly don't mind mentoring guys who are just learning but everything I know is out there on the web somewhere in a tutorial (well aside from the few methods I have actually created for doing certain things). Some of those tutorials are a little dense for the hobbyists like those of us in eWrestling and so I'm going to take a stab at interpreting and re-presenting that knowledge in a slightly easier to understand form. If you really search you are going to find tutorials that present a lot of the same info I am going to cover in this series but the difference is that I am trying to present in a way which is relevant to today's eWrestling based Poser artists.

For the first installment in this tutorial series I'd like to talk about a fairly easy to implement technique that can add realism to your renders no matter your skill level. This will require Poser 6 or 7 as the advanced features needed to create this effect will not be found in versions prior to Poser 6. So what's the effect?

Ambient Occlusion

Now the obvious next question is "What the hell is Ambient Occlusion?" Well here's the stuffy definition:

Ambient Occlusion: A shading method used in 3D computer graphics which helps add realism to local reflection models by taking into account attenuation of light due to occlusion.

At this point, even after reading that, you will no doubt ask me again, "What the hell is Ambient Occlusion?" Ok, let me just put it simply; Ambient Occlusion is a simulation that attempts to duplicate that small shadow your upper lip casts on your lower lip right where they meet. It's simulating the tiny shadows cast inside the intricate curves of your ear or the subtle shadow a ring casts on the skin of your finger. Basically Ambient Occlusion is a method for casting additional shadows in a scene which are not dependent on light but instead are dependent on the proximity of objects to one another (ie. the closeness of a necklace to your skin) in an attempt to create more realistic shadows.

Let me start off by showing you a dramatic example. The topimage features no AO just lights and the bottom features the same lights with AO.

Look at the image on the right and examine the shading underneath the coiled shin guards, look at the darkness between the toes, that's Ambient Occlusion which creates those shadows NOT the main lights in the scene. This is a perfect illustration of what AO can bring to your renders and why learning to use it is worth while. I never render without AO and that example should plainly show you why.

Well let's dive right in and start creating images with AO! Before you do anything else go into your Render Settings and turn Ray Tracing ON. The AO effect is created with Ray Tracing so if you don't have it on in your Render Settings the AO will not show up. After turning that on we can investigate the easiest way to generate broad, unrefined AO which is to find a light in your scene, select it, go to it's Properties and check "Ambient Occlusion." Now this works, and it's fine, but because using this option actually causes the light to generate the AO you get the same AO intensity over the whole piece. For your first experiments with AO producing renders using this method is perfectly fine but ultimately you will want the versatility of node based AO.

Let me just briefly introduce you to the concept of nodes, what they are, and how useful they can be. Nodes are a part of Poser's Material Room and they are advanced features which can be used to create more complex effects which range from the unevenness of human skin to the plush surface of velvet and even going as far as creating full textures themselves. Nodes are designed to enhance the 2D textures used in Poser models or in some cases even replace them completely. A bundle of interconnected nodes is usually referred to as a 'shader' and those who have used Victoria 4 have, whether you understander it or not, used a very complex skin shader which comes built into the character's texture.

To start us out just go to Poser's Material Room and click over from the Simple tab to the Advanced tab. If you have nothing loaded or selected you'll just have an empty space, if you have some type of figure selected you'll see the basic 'Poser Surface' box down the left hand side. Now right click in the open space of the Material window and look for 'New Node' and then mouse over it to pop out all the node options. Take a minute to mouse to the different node types and just look at some of the possibilities, paying closer attention to the Math, Lighting, and 2D & 3D Texture nodes and their sub selections as they are the most used.

Now let's add our Ambient Occlusion node! First we'll need a figure selected, so load one if you haven't already gotten one up, and then head to the Material Room. Move from Simple to Advanced and right click in the Material window and find New Node. Ambient Occlusion is a type of shadowing so we want to head to Lighting. The shadows produced by AO are generated through Ray Tracing so mouse to Ray Trace. Once under Ray Trace you will see ambient_occlusion, click on it to create your AO node. If you couldn't follow that just glance at the image below:

When the AO node populates it's going to have default values plugged in and those default values are going to work fine for most things. When trying to understand how to tweak AO the values to pay attention to are MaxDist and RayBias. I can't tell you hard and fast values to use to get certain results because the values are going to vary depending on the system of measure your version of Poser is set to use so just play around to understand what values work best.

MaxDist literally means just that, this number is the distance the shadow will extend away from the source (ie. the coiled shin shin guard). So increasing MaxDist will darken the shadowing near the source and cause the shadow to extend out farther from the source.

As you can see a MaxDist of 0.5 (my default unit of measure is feet) limits the distance the AO effect travels and creates subtle shadowing adding an extra touch of realism. MaxDist at 1.0 gives the AO more power so that it travels farther out giving you a more pronounced shadowing which works better for full body shots where the camera is zoomed out.

RayBias is a little more difficult to understand and I admittedly am not well versed in all its implications. What I do understand is that a higher RayBias darkens the AO and a lower RayBias will lighten it. Get the RayBias too low and you get 'artifacts' which are little rendering errors. Look at the three images below for some examples of RayBias settings and then just play with them on your own to try and unlock a bit more about how they function.

Higher RayBias

As you can see on the Higher RB image the AO is a bit darker and is reacting more intensely to parts of the shin guard which are a little farther from the skin. With Default you have a nice even balance and then with the Lower RB image you can see the little vertical lines which are artifacts we would not want in our render. So if you want subtle AO you would want to push your RayBias as low as possible without breaking the threshold where artifacts start to appear.

There you go, you have an AO node in place and you've gained a basic knowledge of its settings and how to begin to tweak them. Unfortunately if you run a render with this AO node as it is you will get nothing! You lose! Good day sir! We need to attach this node to something in order for it to work so actually creating it was just our first step.

With AO nodes you want to link it to the item that you want to react to AO, not the item which is causing the AO. So if I want a necklace to cast AO shadows on skin I attach the AO node to the skin NOT the necklace. We're basically telling the skin how to react when it comes in close contact with the necklace by telling it to darken when the necklace is within X distance (X being the values of our AO node).

So we're going to select the skin (or whichever part) of the figure in the Advanced tab of the Material Room. With the target AO part (like SkinTorso) of our figure selected we now have the Poser Surface box down the left hand side. Ambient Occlusion nodes must be attached to TWO parts of the Poser Surface box: Diffuse_Value and Specular_Value. Look at your AO node and find the little 'plug-in' icon on the upper left hand corner of the node. Click and drag and you will see that you have a little line following you and you can take this line over and plug it into one of the little 'socket' icons on the Poser Surface box. Once you've plugged the first line into Diffuse_Value drag another cord over and plug it into Specular_Value as shown below.

Don't worry about the actual numbers entered for Diffuse and Specular value, those will be fine at defaults. This node, as is pictured, is the node which created the Lower RB image, notice the RayBias of 0.005. So there you go, that's it, you've just given one Material zone of your figure an AO node which will generate AO shadowing and enhance realism. Yes, I said ONE material zone... most figures have a dozen of more material zones. Yes, if you apply AO by hand you will have to generate, setup, and attach the node to every material zone you want to have AO appearing on. That sucks eh?

Well it's actually not as bad as it sounds. You really only want AO on certain parts of the body and you definitely only need to apply it to parts that show. What's more there is a 'Wacro' in the list on the left hand side of the Material window that says 'Set Up Ambient Occlusion' and it will do just that. That Wacro will add a default AO node AND attach it to the two values it needs to be on but it also only works for the currently selected material zone. The ultimate way to easily generate AO for the whole body of a figure is to use Face_Off's script from Renderosity which is called Occlusion Master. Occlusion Master gives you one interface where you can tweak values and then it will create all the nodes, attach them, and turn Ray Tracing on.

Now why did I run through this whole thing only to tell you at the very end that there's a program that will do this for you? Because just finding a program that will do things that you do not understand does not make you a better artist it just makes you dependent on 'tricks'. I use Occlusion Master but not because I do not understand AO, I use it because it is a time saver. I believe that understanding the tools you utilize, especially those that automate complex processes, is paramount to becoming a truly gifted practitioner in ANY field be it Poser, web design or hell even something as far removed from computer graphics as auto racing. You now understand AO, you know what it is and how it works, if you choose to use Occlusion Master it won't be a crutch that you lean on but instead it will be another strut in the stable foundation you are building as a skilled user of Poser.

So now go out into the Poser world and start using AO, use it on skin, use it on clothing, use it on anything which is going to be in close proximity to anything else. Experiment and above all else try to have fun!

Source: http://www.thatposerguy.com/tutorials/ao/ao.html