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Sparse Voxel Octrees

Terrain implementation for games is a subject with a lot of depth. At the surface, it's very easy to get rudimentary terrain working via a noise function and fixed triangle grid. As you add more features, though, the complexity builds quickly. Overhangs, caves Multiple materials Destructive terrain Collision detection Persistence Dynamic loading Regions, biomes Very large scale Smooth features Sharp features Dynamic level of detail Extremely long view distances In isolation, each of these features can make terrain difficult to implement. Taken together, it takes a lot of care and attention to make it all work. Minecraft is probably the canonical example for terrain generation in the last generation of games. In fact, I'd say Minecraft's terrain is the killer feature that makes the game so great. Minecraft does an excellent job at 1-8, but for a recent planetary renderer project I was working on, I really wanted 9-12 too. In a series of articles, I'm planning to break do
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Entity / Component Systems

I've been writing a new game recently -- and this time, I decided to use an entity/component system . Boy, does that approach make things easier! In other games I've written, I've struggled to fit new gameplay features into the existing code base. With a entity-component based systems, it's easy to add new features: Need a way to track targetable objects in your game? Add a Targetable component that advertises the unit's position, name for display in the HUD, etc. Need to add some new AI behavior to a unit? Add a component! Update all the AI components once per frame and you're on your way. Does your game need networking? What should you do...? Add a component containing all the info for network serialization! Need to control a unit from user input? Add a joystick component that updates the unit's position component in response to user input. Basically, any new feature can be folded into a component. The best thing about components is that they are dy

Minecraft Terrain

Yesterday, on my day off, I played around with generating some Minecraft-like terrain. A lot of people see Minecraft and think "Hey, that doesn't look too complicated...I could do that!" As a result, we have lots of Minecraft clones and articles about implementing Minecraft-like terrain. I think that's great, because it inspires people who don't have much graphics programming experience to give it a try. A game like Crysis doesn't exactly do that. It's just too much complexity for a single person to handle. Anyway, the first step in my journey to copy Minecraft was to implement a "mesher." A mesher converts a 3D bitmap containing block data into a quad mesh that's displayable using OpenGL. This part was surprisingly easy, at least for the simple approach I took. I decided to sweep each "column" of blocks in the X, Y, and Z directions, and generate the quad faces that way. This doesn't allow quad faces to span across m

Password Generator for Chrome

This week, I finally got fed up with typing in/managing passwords on a billion different sites. Since things like OpenID haven't really taken off, I decided to take matters into my own hands...and write a password generator extension for Google Chrome. There are actually a ton of such apps on the Chrome web store, but I'm paranoid about security, so I wrote my own and open-sourced it. By virtue of being open source, perhaps people will trust my version a bit more. Anyway, the extension is available here , and the source code is hosted at github . May all your online transactions be secure! UPDATE: Fixed github link.

Lua-Style Coroutines in C++

Lua's implementation of coroutines is one of my all-time favorite features of the language. This (short) paper explains the whole reasoning behind the Lua's coroutine implementation and also a little about the history of coroutines. Sadly, coroutines are not supported out-of-the box by many modern languages, C++ included. Which brings me to the subject of this post: Lua-style coroutines in C++! For those who don't know (or were too lazy to read the paper!), Lua's coroutines support three basic operations: Create: Create a new coroutine object Resume: Run a coroutine until it yields or returns Yield: Suspend execution and return to the caller To implement these three operations, I'll use a great header file: ucontext.h. #include <vector> #include <ucontext.h> class Coroutine { public: typedef void (*Function)(void); Coroutine(Function function); void resume(); static void yield(); private: ucontext_t context_; std

Jet: Cascading Shadow Maps

This is a demo of my homegrown cascading shadow mapping.  Notice how the shadows remain sharp at all distances.  This is currently using 4 2048 byte shadow textures, but it looks similar with 1024 byte textures. Cascading shadow maps work by dividing the view frustum into sections, and assigning a shadow texture to each section.  This allows shadows to be rendered at great distance without loss of visual fidelity during close-up shots of a shadow.  The great thing about shadow mapping is that you get self-shadowing for free. The performance isn't too bad either.  This demo ran at 270 frames per second on my EVGA 8800 GTS, with normal mapping and specular mapping.  Modern GPUs have really great texture lookup performance: the shader I wrote for this demo performs 7 texture lookups per pixel (1 for normal mapping, 1 for the diffuse map, 1 for specular mapping, and 4 for shadow mapping).  A previous iteration of this demo (with only 1 shadow texture lookup) ran on an Intel GMA at 35

Jet: Particle Systems

Here's a demo of the new particle systems I've implemented in OpenGL.  Performance is much improved over the DirectX version.  Particles are initialized in C++ rather than in Lua.  Also, I use two particle buffers and swap between them, rather than using one buffer per particle system.  Anyway, here's a video capture: