step method
Advances the simulation by dt seconds in fixed-size steps, draining a
clamped accumulator so the outcome is frame-rate independent.
Implementation
void step(double dt) {
var frame = dt;
if (frame < 0.0) frame = 0.0;
if (frame > maxFrameTime) frame = maxFrameTime;
_accumulator += frame;
while (_accumulator >= fixedStep) {
_stepFixed(fixedStep);
_accumulator -= fixedStep;
}
}