at method
How far the glide has taken the camera from where it was released, at
t of its duration.
Implementation
MapGestureStep at(double t) {
double eased(double tau) => tau * (1 - math.exp(-t * _seconds / tau));
final k = eased(glideSeconds);
return MapGestureStep(
from: focal,
to: focal + pan * k,
zoomBy: zoom * eased(_zoomSeconds),
turn: turn * eased(_turnSeconds),
tilt: tilt * eased(_tiltSeconds),
);
}