Skip to main content

Jet Game Engine: Simple Destructible Meshes

I've been meaning for a while to mess around with destructible meshes (they're way cool!). Making physically accurate destructible meshes is hard. Instead, I've opted for a simple scheme that still has great visual results for compact objects. The technique works like this:
  1. Choose a plane to split the mesh along.
  2. Create two new meshes to hold the fragments.
  3. For each triangle in the mesh: if the triangle is entirely above the plane, add it to the first mesh.  Otherwise, add it to the second mesh.
  4. Create a new scene node/rigid body for each of the fragments.
I added some optimizations as well.  To begin, you don't have to copy the triangle data for both fragments. They share the exact same mesh data, just different halves of it.  Instead, I create a new index buffer for each fragment and then re-use the same vertex buffer. This works really well and is relatively light on the video memory. Another thing I did is to re-use the original destructible mesh object. Thus, for each fracture, only one new destructible mesh object is created.

Obviously, this technique has limitations.  You can't break a mesh into more than two pieces at once, and the hole created by the split is a) not closed and b) pretty jagged.  Jagged edges around the split is OK for wreckage.  An open mesh also looks OK, as long as both the fronts and backs of triangles are rendered (i.e., turn off back-face culling).  I have considered writing some code that will close the hole in the mesh by creating new vertices to cover the hole.  However, this modifies the triangle buffer, which might not be good for performance.

I'm sure someone else has thought of it before.  It's a pretty simple technique, but it still looks decent!
 

Comments

Post a Comment

Popular posts from this blog

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...
9 comments
Read more

Warp

So, it turns out that I didn't use Criterium for the video game competition at Stanford.  I actually met a partner and went with another concept instead -- Warp.  It's kind of like Starfox and it's inspired by Rez, one of the first PS2 games.  Explosions and missiles fire in time with the music; we used ChucK , an audio processing language, to achieve this. We also made some destructible objects using rigid bodies, and I added some particle explosion effects.  We used Lua to for enemy AI, and wrote a small TCL-like script parser that reads in data for the level layout.  The buildings in the background are procedurally generated.  We used OGRE for the graphics (this was a loose requirement of the project) and Bullet for the physics.  I had a lot of fun with this project, and I've posted a video capture below.
1 comment
Read more

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...
Post a Comment
Read more