Article: Shaders – Rim Lighting
by Daniel Greenheck
What should I be familiar with before I go through this tutorial?
- The content discussed in the ambient, diffuse and specular tutorials.
- Dot products, vectors
What is Rim Lighting?
Rim lighting is a shader technique you often see in role-playing games when there's a treasure chest or door which needs to be opened. Around the border of the object there is a soft glow which differentiates it from the rest of the objects in the scene. The concept behind the rim lighting shader is extremely simple: the more a surface faces away from the camera, the more rim lighting it should get. Looking at the sphere below illustrates the point:
Article: Shaders – Texturing
by Daniel Greenheck
A simple box with a stone black texture
This tutorial will cover attaching an image (I'll be using the word texture from now on) to a model to give it a much more detailed look. Texturing is an essential of creating a realistic scene because it allows us to give objects very fine detail. Without textures, everything in the scene would basically be one color, look very flat and just be generally boring. The right textures can even give an object the illusion of depth, further increasing the realism. The stone box above looks like it has deep cracks in it between the blocks, but that's just an illusion. The entire box is defined using eight vertices. To geometrically represent those cracks, it would take thousands of vertices, something that definitely isn't feasible.
Article: Shaders – Specular Lighting
by Daniel Greenheck
What should I be familiar with before I go through this tutorial?
- The content discussed in the introduction, ambient and diffuse tutorials.
One Thing Before I Begin...
To keep things succinct, I will no longer explain or comment things explained in previous tutorials. Throughout these series of tutorials, I'm going to expect you've gone through the previous tutorials. No sense in beating a dead horse. So if you look at the variables section and only see the Specular variables, rest assured the others are still in the actual program. I just think it will be easier for you as a reader if I only present you with new information. That aside, let's begin!
What is Specular Lighting?
Specular lighting in one word: shiny. The world specular in itself means a mirror-like surface, so you can imagine that anything that has specular lighting is very reflective, causing it to have shiny highlights. If you place a polished chrome ball under a direct light source, you'll probably see a big shiny spot blinding you; this is the specular highlight. Specular reflections are caused by the reflection of the actual light source itself. If the surface isn't flat however, it will warp the light and you'll usually see it as a small dot of bright light or curved lines of light. When you're out on a sunny day, look around at smooth, metallic objects and notice their specular highlights. Try and determine how the light is coming in and being reflected off the surface to your eye. The more you understand about real-world lighting, the better you'll understand what we're trying to replicate in our shaders.
The perfect example of specular lighting. Notice the highlight is really the reflection of the sun.
Article: Shaders – Diffuse Lighting
by Daniel Greenheck
What should I be familiar with before I go through this tutorial?
- The content discussed in the introduction and ambient shader tutorials.
- A simple knowledge of vectors, matrices and dot products (click on the links for Wiki articles) will REALLY help you understand some of the light calculations going on. although I'll do my best to explain those topics in this tutorial.
What is Diffuse Lighting?
Diffuse lighting can best be described as directional light. There are three types of diffuse lighting: directional, point light and spotlight. I have a picture of each below in respective order. Directional light comes down at the same angle no matter where you are standing; the light has no position, just direction. Point light is like a light bulb, it all emanates from a single point equally in all directions. A spot light is like an oriented floodlight or a flashlight. Diffuse light also creates shadows, but that's a much more advanced topic we won't dive in to until later.
Article: Shaders – Ambient Lighting
by Daniel Greenheck
Since these are shader tutorials and not XNA tutorials, I'm guessing you already have a basic understanding of these topic
- How to draw a simple model or some vertices in XNA.
- How to add files to the Content Pipeline.
- The content in my Shader Introduction.
A few words to start...
Before someone makes the wise-crack that ambient lighting is already taken care of in the BasicEffect class in XNA, I'm going to tell you: ambient lighting is already taken care of in the BasicEffect class in XNA. The reason I'm giving this tutorial is because these basic shaders lay the foundation for more advanced and complex shaders. If you can understand how simple shaders work, it will help you out profoundly when dealing with complex topics like bump mapping and projective texturing later on. I highly recommend avoiding the BasicEffect class if you are completely new to shaders. Instead focusing on building your foundation of shader knowledge; it's completely necessary if you ever plan on making anything beyond a game that looks like Mario 64.
If you don't plan on using advanced shaders or you already know the basics of HLSL, here’s a tutorial on how to use the BasicEffect class (which is also on my links page).
Now, for those of you who are still with me! Ambient lighting is about as simple as it gets, so this will be a good place to start if you are completely unfamiliar with HLSL. A scene with only ambient lighting by itself looks like a polar bear in a snow storm, so if you want a little more detailed effect, I would skip to the diffuse lighting tutorial. However, in later tutorials, I'll be focusing mainly on the actual code inside the vertex and pixel shaders; I'm going to assume you've already read this tutorial and have a basic understanding of shaders. So consider yourself warned!