Ludum Dare 23: Tiny World

I'm taking part in Ludum Dare this weekend. The theme is Tiny World. Here's what I've managed so far:

This represents about two hours worth of work so far. Most of that time I've spent brainstorming because I was a bit stumped by the theme, but I've got a few ideas now and I'm forging ahead. Wish me luck.

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Assert no lock required

This is a technique I learnt about from Jason Gregory's excellent book, Game Engine Architecture (3rd Edition) . If you have a shared resource accessed by multiple threads, where you're fairly certain that it's only ever accessed by one thread at a time, you can use an assert() to check for this at debug time without having to pay the runtime cost of locking a mutex. The implementation is fairly straightforward: class UnnecessaryMutex { public: void lock() { assert(!_locked); _locked = true; } void unlock() { assert(_locked); _locked = false; } private: volatile bool _locked = false; }; #ifdef ENABLE_LOCK_ASSERTS #define BEGIN_ASSERT_LOCK_NOT_REQUIRED(mutex) (mutex).lock() #define END_ASSERT_LOCK_NOT_REQUIRED(mutex) (mutex).unlock() #else #define BEGIN_ASSERT_LOCK_NOT_REQUIRED(mutex) #define END_ASSERT_LOCK_NOT_REQUIRED(mutex) #endif Usage is equally straightforward: UnnecessaryMutex gMutex; void PossiblyOverlappingFunction...

How to outperform std::vector in 1 easy step

Everyone who's familiar with C++ knows that you should avoid resizing a std::vector inside a loop wherever possible. The reasoning's pretty obvious: the memory allocated for the vector doubles in size each time it fills up and that doubling is a costly operation. Have you ever wondered why it's so costly though? It's tempting to assume that because implementations of the STL have been around for so long that they must be pretty efficient. It turns out that's a bad assumption because the problem, in this case, is the standard itself: specifically, the allocator interface. The allocator interface provides two methods that obtain and release memory: allocate allocates uninitialized storage (public member function) deallocate deallocates storage (public member function) (taken from this page ). What's missing is a way of growing an existing memory allocation in place. In C this is provided by the realloc function, but there's no equiva...

OpenGL ES and occlusion queries

This is a follow-up to my earlier post "WebGL doesn't have query objects" . Since I wrote that post, the situation has changed a bit. It's still true to say that WebGL doesn't have query objects, but the underlying reason - that OpenGL ES doesn't - is no longer true. For OpenGL ES 2.0 , there's an extension which provides basic query functionality: EXT_occlusion_query_boolean (which seems to have been based on ARB_occlusion_query2 from regular OpenGL). For OpenGL ES 3.0 , the functionality from that extension appears to have been adopted into the standard. The extension provides two query types, both of which set a boolean value to indicate whether any pixels passed the depth and stencil tests. While this is progress, unfortunately it's still not sufficient to implement the pixel accurate collision detection method I described in an earlier post. For that purpose it's not enough to know whether any pixels passed the tests; you want to kno...

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