ArcRotateCamera zoom-out speed is much faster than zoom-in speed when using wheelDeltaPercentage

When setting wheelDeltaPercentage on the ArcRotateCamera, the camera appears to zoom out much faster than it zooms in (this effect increases with higher values of wheelDeltaPercentage). In fact with a wheelDeltaPercentage of around 0.1, the zoom-in speed is so slow that it does not appear to be zooming in at all.

Here’s a reproduction in the playground
This appears to affect both Firefox and Chrome, but the difference is greater in Firefox.

Welcome aboard!

There is indeed a special treatment when zooming in:

delta = this.computeDeltaFromMouseWheelLegacyEvent(wheelDelta,;

// If zooming in, estimate the target radius and use that to compute the delta for inertia
// this will stop multiple scroll events zooming in from adding too much inertia
if (delta > 0) {
    var estimatedTargetRadius =;
    var targetInertia = + delta;
    for (var i = 0; i < 20 && Math.abs(targetInertia) > 0.001; i++) {
        estimatedTargetRadius -= targetInertia;
        targetInertia *=;
    estimatedTargetRadius = Scalar.Clamp(estimatedTargetRadius, 0, Number.MAX_VALUE);
    delta = this.computeDeltaFromMouseWheelLegacyEvent(wheelDelta, estimatedTargetRadius);

I don’t know however if that is expected that the speed is different when zooming in vs zooming out… Note that if you use wheelDeltaPercentage=0.01 for eg, the speed will be the same (at least visually)…