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Showing posts from May, 2010

Mesh collisions

This is usually where physics gets messy. It's all fun and games until someone suggests that maybe all objects are not perfectly convex, such as... the game level? There is convex decomposition, yes, but I'm not totally convinced that's a silver bullet. Convex decomposition is awfully complicated, and requires heavy preprocessing. It's definitely a good idea in many cases, but there will always be raw triangles. Convex decomposition or not, you need some sort of mid-phase, finding which triangles/primitives collide with a specific object. A lot of work has been put into this, and I think most people today agree that a quantized, binary AABB tree is the ideal solution. What's interesting here is how people usually query these AABB trees. The output from the broad phase is a list of pairs with overlapping bounding volumes. These pairs are then processed one by one, and in the case of a triangle mesh, the mid-phase is engaged to find the relevant triangles/primitives

Movie time

It was a long time since I posted a movie, so I thought I'd record a little snippet of what I'm working on at the moment - mesh collisions. Without the fancy SSAO renderer it runs in 60 FPS. Stay tunes for details!


I really like the idea of using standardized versions of simple data structures. Small snippets of code rewritten over and over again by thousands of people. I bet there are a handfull of programmers world-wide at this moment implementing a dynamic array or a hash table. As much as I like the idea, I hate the only standard out there - STL. There are several problems: 1) The interface is horribly over-engineered and just plain sucks . Even the simplest of simple operations turns out as three or for lines of code. Really long ones . Say I want to remove an element from a vector. Instead of just offering a dead simple myVector.erase(element) I have to bother with iterators and find functions (of course defined in another include file), ending up with this: std::vector ::iterator it = find(myVector.begin(), myVector.end(), element); if (it != vec.end()) vec.erase(it); This does only remove the first occurance of "element", which is understandable. If you want to remove all o