TeleportingController.java

// Copyright 2009 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.android.stardroid.control;

import com.google.android.stardroid.control.AstronomerModel.Pointing;
import com.google.android.stardroid.units.GeocentricCoordinates;
import com.google.android.stardroid.units.Vector3;
import com.google.android.stardroid.util.MiscUtil;
import com.google.android.stardroid.util.VectorUtil;

import android.util.Log;

/**
 * Flies the user to the search target in manual mode.
 *
 * @author John Taylor
 */
public class TeleportingController extends AbstractController {
  private static final String TAG = MiscUtil.getTag(TeleportingController.class);

  /**
   * Teleport the astronomer instantaneously from his current pointing to a new
   * one.
   *
   * @param targetXyz The destination pointing.
   */
  public void teleport(final GeocentricCoordinates targetXyz) {
    Log.d(TAG, "Teleporting to target " + targetXyz);
    Pointing pointing = model.getPointing();
    final GeocentricCoordinates hereXyz = pointing.getLineOfSight();
    if (targetXyz.equals(hereXyz)) {
      return;
    }

    // Here we calculate the new direction of 'up' along the screen in
    // celestial coordinates.  This is not uniquely defined - it just needs
    // to be perpendicular to the target (which is effectively the normal into
    // the screen in celestial coordinates.)
    Vector3 hereTopXyz = pointing.getPerpendicular();
    hereTopXyz.normalize();
    final Vector3 normal = VectorUtil.crossProduct(hereXyz, hereTopXyz);
    Vector3 newUpXyz = VectorUtil.crossProduct(normal, targetXyz);

    model.setPointing(targetXyz, newUpXyz);
  }

  @Override
  public void start() {
    // Nothing to do.
  }

  @Override
  public void stop() {
    // Nothing to do.
    // We could consider aborting the teleport, but it's OK for now.
  }
}