protected void zoomCamera(float value) {
        if (!enabled) {
            return;
        }

        zooming = true;
        targetDistance += value * zoomSensitivity;
        if (targetDistance > maxDistance) {
            targetDistance = maxDistance;
        }
        if (targetDistance < minDistance) {
            targetDistance = minDistance;
        }
        if (veryCloseRotation) {
            if ((targetVRotation < minVerticalRotation) && (targetDistance > (minDistance + 1.0f))) {
                targetVRotation = minVerticalRotation;
            }
        }
    }
Sets custom triggers for zooming out the cam
default is
new MouseAxisTrigger(MouseInput.AXIS_WHEEL, false)  mouse wheel down

@param triggers the triggers to assign
jme3-core/src/main/java/com/jme3/input/ChaseCamera.java