public void setZoomInTrigger(Trigger... triggers) {
        zoomInTrigger = triggers;
        if (inputManager != null) {
            inputManager.deleteMapping(CameraInput.CHASECAM_ZOOMIN);
            inputManager.addMapping(CameraInput.CHASECAM_ZOOMIN, zoomInTrigger);
            inputManager.addListener(this, CameraInput.CHASECAM_ZOOMIN);
        }
    }
Sets custom triggers for zooming in the cam default is new
MouseAxisTrigger(MouseInput.AXIS_WHEEL, true) mouse wheel up

@param triggers the desired triggers
jme3-core/src/main/java/com/jme3/app/ChaseCameraAppState.java