First Animation Metrics
Entry posted by Josh ·
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I got skinned animation working in the new renderer, after a few failed attempts that looked like something from John Carpenter's The Thing. I set up a timer and updated a single animation on a model 10,000 times. Animation consists of two phases. First, all animations are performed to calculate the local position and quaternion rotation. Second, 4x4 matrices are calculated for the entire hierarchy in global space and copied into an array of floats. To test this, I placed this code inside the main loop:
float frame = Millisecs() / 10.0f; auto tm = Millisecs(); for (int n = 0; n < 10000; ++n) { monster->skeleton->SetAnimationFrame(frame, 1, 1, true); monster->UpdateSkinning(); } int elapsed = Millisecs() - tm; Print(elapsed);
The result in release mode was around 60 milliseconds. When I tested each command lone, I found that UpdateSkinning() took around 30-35 milliseconds while SetAnimationFrame() hovered around 20 milliseconds.
When I cut the number of iterations in half, the result was right around 30 milliseconds, which is within our window of time (33 ms) for games that run at 30 hz. If your game uses a 60 hz loop then you can cut that number in half. The model I am using also only has 24 bones, but models with up to 256 bones are supported (with a pretty linear performance cost).
Now this is with a single call to SetAnimationFrame. If the animation manager is in use there could potentially be many more calculations performed as animations are smoothly blended.
Splitting the animations up into multiple threads could be done easily, but most computers only have four CPUs, so I don't see this being useful on more than 2-3 threads. Let's say we dedicate two threads to animation. That means right now our theoretical limit is about 10,000 zombies onscreen at once. I would like to go higher, but I think this is probably our realistic limit for CPU-performed animations. The alternative would be to upload the animation sequences themselves to the GPU and perform all animation entirely on the GPU, but then we would lose all feedback on the CPU side like the current bone orientations. Perhaps a solution would be to have both a CPU and GPU animation system that produces identical results, and the CPU side stuff would only be called when needed, but that makes things pretty complicated and I am not sure I want to go down that road.
In reality, the final results will probably be quite a lot less than this when all functionality is added, but from this data we can reasonably extrapolate that Leadwerks 5 will support thousands of animated characters onscreen. According to the developers of the Dead Rising series, a few thousand is the practical limit of how many characters you would ever want onscreen, so this is encouraging. Of course, there is no limit on the number of offscreen characters, since animation is only performed for characters that appear onscreen.
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