BaseOrbitViewCollisionSupport.java

/*******************************************************************************
 * Copyright 2014 Geoscience Australia
 * 
 * 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 au.gov.ga.earthsci.worldwind.common.view.orbit;

import gov.nasa.worldwind.geom.Angle;
import gov.nasa.worldwind.geom.Matrix;
import gov.nasa.worldwind.geom.Position;
import gov.nasa.worldwind.geom.Vec4;
import gov.nasa.worldwind.globes.Globe;
import gov.nasa.worldwind.render.DrawContext;
import gov.nasa.worldwind.util.Logging;
import gov.nasa.worldwind.view.orbit.BasicOrbitView;
import gov.nasa.worldwind.view.orbit.OrbitView;
import gov.nasa.worldwind.view.orbit.OrbitViewCollisionSupport;
import gov.nasa.worldwind.view.orbit.OrbitViewInputSupport;

/**
 * Same as {@link OrbitViewCollisionSupport}, but replacing any references to
 * {@link BasicOrbitView} with the {@link OrbitView} interface.
 * 
 * @author Michael de Hoog (michael.dehoog@ga.gov.au)
 */
@SuppressWarnings("nls")
public class BaseOrbitViewCollisionSupport
{
	private double collisionThreshold;
	private int numIterations;

	public BaseOrbitViewCollisionSupport()
	{
		setNumIterations(1);
	}

	public double getCollisionThreshold()
	{
		return this.collisionThreshold;
	}

	public void setCollisionThreshold(double collisionThreshold)
	{
		if (collisionThreshold < 0)
		{
			String message = Logging.getMessage("generic.ArgumentOutOfRange", collisionThreshold);
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}

		this.collisionThreshold = collisionThreshold;
	}

	public int getNumIterations()
	{
		return this.numIterations;
	}

	public void setNumIterations(int numIterations)
	{
		if (numIterations < 1)
		{
			String message = Logging.getMessage("generic.ArgumentOutOfRange", numIterations);
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}

		this.numIterations = numIterations;
	}

	public boolean isColliding(OrbitView orbitView, double nearDistance, DrawContext dc)
	{
		if (orbitView == null)
		{
			String message = Logging.getMessage("nullValue.OrbitViewIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		if (nearDistance < 0)
		{
			String message = Logging.getMessage("generic.ArgumentOutOfRange", nearDistance);
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		if (dc == null)
		{
			String message = Logging.getMessage("nullValue.DrawContextIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		Globe globe = dc.getGlobe();
		if (globe == null)
		{
			String message = Logging.getMessage("nullValue.DrawingContextGlobeIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}

		Matrix modelviewInv = getModelviewInverse(globe,
				orbitView.getCenterPosition(), orbitView.getHeading(), orbitView.getPitch(), orbitView.getRoll(),
				orbitView.getZoom());
		if (modelviewInv != null)
		{
			// OrbitView is colliding when its eye point is below the collision threshold.
			double heightAboveSurface = computeViewHeightAboveSurface(dc, modelviewInv,
					orbitView.getFieldOfView(), orbitView.getViewport(), nearDistance);
			return heightAboveSurface < this.collisionThreshold;
		}

		return false;
	}

	public Position computeCenterPositionToResolveCollision(OrbitView orbitView, double nearDistance,
			DrawContext dc)
	{
		if (orbitView == null)
		{
			String message = Logging.getMessage("nullValue.OrbitViewIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		if (nearDistance < 0)
		{
			String message = Logging.getMessage("generic.ArgumentOutOfRange", nearDistance);
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		if (dc == null)
		{
			String message = Logging.getMessage("nullValue.DrawContextIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		Globe globe = dc.getGlobe();
		if (globe == null)
		{
			String message = Logging.getMessage("nullValue.DrawingContextGlobeIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}

		Position newCenter = null;

		for (int i = 0; i < this.numIterations; i++)
		{
			Matrix modelviewInv = getModelviewInverse(globe,
					newCenter != null ? newCenter : orbitView.getCenterPosition(),
					orbitView.getHeading(), orbitView.getPitch(), orbitView.getRoll(), orbitView.getZoom());
			if (modelviewInv != null)
			{
				double heightAboveSurface = computeViewHeightAboveSurface(dc, modelviewInv,
						orbitView.getFieldOfView(), orbitView.getViewport(), nearDistance);
				double adjustedHeight = heightAboveSurface - this.collisionThreshold;
				if (adjustedHeight < 0)
				{
					newCenter =
							new Position(
									newCenter != null ? newCenter : orbitView.getCenterPosition(),
									(newCenter != null ? newCenter.getElevation() : orbitView.getCenterPosition()
											.getElevation())
											- adjustedHeight);
				}
			}
		}

		return newCenter;
	}

	public Angle computePitchToResolveCollision(OrbitView orbitView, double nearDistance, DrawContext dc)
	{
		if (orbitView == null)
		{
			String message = Logging.getMessage("nullValue.OrbitViewIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		if (nearDistance < 0)
		{
			String message = Logging.getMessage("generic.ArgumentOutOfRange", nearDistance);
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		if (dc == null)
		{
			String message = Logging.getMessage("nullValue.DrawContextIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}
		Globe globe = dc.getGlobe();
		if (globe == null)
		{
			String message = Logging.getMessage("nullValue.DrawingContextGlobeIsNull");
			Logging.logger().severe(message);
			throw new IllegalArgumentException(message);
		}

		Angle newPitch = null;

		for (int i = 0; i < this.numIterations; i++)
		{
			Matrix modelviewInv = getModelviewInverse(globe,
					orbitView.getCenterPosition(), orbitView.getHeading(),
					newPitch != null ? newPitch : orbitView.getPitch(), orbitView.getRoll(),
					orbitView.getZoom());
			if (modelviewInv != null)
			{
				double heightAboveSurface = computeViewHeightAboveSurface(dc, modelviewInv,
						orbitView.getFieldOfView(), orbitView.getViewport(), nearDistance);
				double adjustedHeight = heightAboveSurface - this.collisionThreshold;
				if (adjustedHeight < 0)
				{
					Vec4 eyePoint = getEyePoint(modelviewInv);
					Vec4 centerPoint = globe.computePointFromPosition(orbitView.getCenterPosition());
					if (eyePoint != null && centerPoint != null)
					{
						Position eyePos = globe.computePositionFromPoint(eyePoint);
						// Compute the eye point required to resolve the collision.
						Vec4 newEyePoint = globe.computePointFromPosition(eyePos.getLatitude(), eyePos.getLongitude(),
								eyePos.getElevation() - adjustedHeight);
						// Compute the pitch that corresponds with the elevation of the eye point
						// (but not necessarily the latitude and longitude).
						Vec4 normalAtCenter = globe.computeSurfaceNormalAtPoint(centerPoint);
						Vec4 newEye_sub_center = newEyePoint.subtract3(centerPoint).normalize3();
						double dot = normalAtCenter.dot3(newEye_sub_center);
						if (dot >= -1 || dot <= 1)
						{
							double angle = Math.acos(dot);
							newPitch = Angle.fromRadians(angle);
						}
					}
				}
			}
		}

		return newPitch;
	}

	private double computeViewHeightAboveSurface(DrawContext dc, Matrix modelviewInv,
			Angle fieldOfView, java.awt.Rectangle viewport, double nearDistance)
	{
		double height = Double.POSITIVE_INFINITY;
		if (dc != null && modelviewInv != null && fieldOfView != null && viewport != null && nearDistance >= 0)
		{
			Vec4 eyePoint = getEyePoint(modelviewInv);
			if (eyePoint != null)
			{
				double eyeHeight = computePointHeightAboveSurface(dc, eyePoint);
				if (eyeHeight < height)
				{
					height = eyeHeight;
				}
			}

			Vec4 nearPoint = getPointOnNearPlane(modelviewInv, fieldOfView, viewport, nearDistance);
			if (nearPoint != null)
			{
				double nearHeight = computePointHeightAboveSurface(dc, nearPoint);
				if (nearHeight < height)
				{
					height = nearHeight;
				}
			}
		}
		return height;
	}

	private double computePointHeightAboveSurface(DrawContext dc, Vec4 point)
	{
		double height = Double.POSITIVE_INFINITY;
		if (dc != null && dc.getGlobe() != null && point != null)
		{
			Globe globe = dc.getGlobe();
			Position position = globe.computePositionFromPoint(point);
			Position surfacePosition = null;
			// Look for the surface geometry point at 'position'.
			Vec4 pointOnGlobe = null;
			try
			{
				pointOnGlobe = dc.getPointOnTerrain(position.getLatitude(), position.getLongitude());
			}
			catch (NullPointerException e)
			{
				//dc.getPointOnTerrain() can sometimes throw a NPE; ignore it
			}
			if (pointOnGlobe != null)
			{
				surfacePosition = globe.computePositionFromPoint(pointOnGlobe);
			}
			// Fallback to using globe elevation values.
			if (surfacePosition == null)
			{
				surfacePosition =
						new Position(position,
								globe.getElevation(position.getLatitude(), position.getLongitude())
										* dc.getVerticalExaggeration());
			}
			height = position.getElevation() - surfacePosition.getElevation();
		}
		return height;
	}

	private Matrix getModelviewInverse(Globe globe,
			Position centerPosition, Angle heading, Angle pitch, Angle roll, double zoom)
	{
		if (globe != null && centerPosition != null && heading != null && pitch != null)
		{
			Matrix modelview = OrbitViewInputSupport.computeTransformMatrix(globe,
					centerPosition, heading, pitch, roll, zoom);
			if (modelview != null)
			{
				return modelview.getInverse();
			}
		}

		return null;
	}

	private Vec4 getEyePoint(Matrix modelviewInv)
	{
		return modelviewInv != null ? Vec4.UNIT_W.transformBy4(modelviewInv) : null;
	}

	private Vec4 getPointOnNearPlane(Matrix modelviewInv, Angle fieldOfView, java.awt.Rectangle viewport,
			double nearDistance)
	{
		if (modelviewInv != null && fieldOfView != null && viewport != null && nearDistance >= 0)
		{
			// If either either the viewport width or height is zero, then fall back to an aspect ratio of 1. 
			// Otherwise, compute the standard aspect ratio.
			double aspect = (viewport.getWidth() <= 0 || viewport.getHeight() <= 0) ?
					1d : (viewport.getHeight() / viewport.getWidth());
			double nearClipHeight = 2 * aspect * nearDistance * fieldOfView.tanHalfAngle();
			// Computes the point on the bottom center of the near clip plane.
			Vec4 nearClipVec = new Vec4(0, -nearClipHeight / 2.0, -nearDistance, 1);
			return nearClipVec.transformBy4(modelviewInv);
		}

		return null;
	}
}