help! my triangle is only 300fps!!!
Don't worry! your triangle running at a mere 300 fps is perfectly normal. The purpose of this post is to try to convince you it is not a good use of your time to try to optimise hello-triangle.
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300fps is still pretty fast! ~3.33ms
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FPS can be a misleading performance metric, as it changes non-linearly as you optimise your frame. A 10fps difference from 60 to 70fps is ~2.38ms while the difference from 300 to 310fps is ~0.107ms. To actually profile your application it is much better to use dedicated tools like Nsight Graphics or Tracy.
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Modern GPUs are very complex, and performance does not scale linearly with scene complexity, for example, if one triangle runs at 300fps this doesnt mean five triangles will run at 60fps. GPUs are designed to have really good throughput at the cost of latency.
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When rendering one single triangle, most of your frametime may just be overhead, this could be your window manager, driver or API state validation to name a few.
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hello-triangle is simply not a representative workload for real applications, which are way more complex with lots of factors affecting performance and a compromise between speed and quality. In order to properly judge the performance of your engine, you should at least use a test scene such as Intel Sponza or Bistro.
Good luck on your journey learning graphics!