Character jitters when framerate dips, physics looks fine
Small 2D platformer in C++ with SDL. I multiply velocity by dt every frame. At steady 60 it's smooth. When it dips, the player stutters and jumps come out at a different height, which breaks some levels.
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Variable dt makes the integration depend on the frame rate. Fixed step with an accumulator:
accumulator += frame_time;
while (accumulator >= STEP) {
update(STEP);
accumulator -= STEP;
}
render(accumulator / STEP);
Pass the leftover fraction to render and interpolate between the previous and current states. Otherwise you get a small jitter whenever the update count changes between frames. There's a well known article called Fix Your Timestep that goes through it.
Read the article. Jump heights are identical now. I'm clamping frame_time to 0.25s as well, otherwise dragging the window gives a spiral of updates.
Is this what Godot does with its physics tick?
Yes, _physics_process runs at a fixed rate, and newer versions have physics interpolation you switch on in the project settings. Solved, thanks jf.
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