| /* |
| * Copyright (c) 2009-2010 jMonkeyEngine |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * * Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * * Neither the name of 'jMonkeyEngine' nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
| * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package com.jme3.terrain.geomipmap.picking; |
| |
| import com.jme3.math.Ray; |
| import com.jme3.math.Vector2f; |
| import com.jme3.math.Vector3f; |
| |
| /** |
| * Works on the XZ plane, with positive Y as up. |
| * |
| * @author Joshua Slack |
| * @author Brent Owens |
| */ |
| public class BresenhamYUpGridTracer { |
| |
| protected Vector3f gridOrigin = new Vector3f(); |
| protected Vector3f gridSpacing = new Vector3f(); |
| protected Vector2f gridLocation = new Vector2f(); |
| protected Vector3f rayLocation = new Vector3f(); |
| protected Ray walkRay = new Ray(); |
| |
| protected Direction stepDirection = Direction.None; |
| protected float rayLength; |
| |
| public static enum Direction { |
| None, PositiveX, NegativeX, PositiveY, NegativeY, PositiveZ, NegativeZ; |
| }; |
| |
| // a "near zero" value we will use to determine if the walkRay is |
| // perpendicular to the grid. |
| protected static float TOLERANCE = 0.0000001f; |
| |
| private int stepXDirection; |
| private int stepZDirection; |
| |
| // from current position along ray |
| private float distToNextXIntersection, distToNextZIntersection; |
| private float distBetweenXIntersections, distBetweenZIntersections; |
| |
| public void startWalk(final Ray walkRay) { |
| // store ray |
| this.walkRay.set(walkRay); |
| |
| // simplify access to direction |
| Vector3f direction = this.walkRay.getDirection(); |
| |
| // Move start point to grid space |
| Vector3f start = this.walkRay.getOrigin().subtract(gridOrigin); |
| |
| gridLocation.x = (int) (start.x / gridSpacing.x); |
| gridLocation.y = (int) (start.z / gridSpacing.z); |
| |
| Vector3f ooDirection = new Vector3f(1.0f / direction.x, 1,1.0f / direction.z); |
| |
| // Check which direction on the X world axis we are moving. |
| if (direction.x > TOLERANCE) { |
| distToNextXIntersection = ((gridLocation.x + 1) * gridSpacing.x - start.x) * ooDirection.x; |
| distBetweenXIntersections = gridSpacing.x * ooDirection.x; |
| stepXDirection = 1; |
| } else if (direction.x < -TOLERANCE) { |
| distToNextXIntersection = (start.x - (gridLocation.x * gridSpacing.x)) * -direction.x; |
| distBetweenXIntersections = -gridSpacing.x * ooDirection.x; |
| stepXDirection = -1; |
| } else { |
| distToNextXIntersection = Float.MAX_VALUE; |
| distBetweenXIntersections = Float.MAX_VALUE; |
| stepXDirection = 0; |
| } |
| |
| // Check which direction on the Z world axis we are moving. |
| if (direction.z > TOLERANCE) { |
| distToNextZIntersection = ((gridLocation.y + 1) * gridSpacing.z - start.z) * ooDirection.z; |
| distBetweenZIntersections = gridSpacing.z * ooDirection.z; |
| stepZDirection = 1; |
| } else if (direction.z < -TOLERANCE) { |
| distToNextZIntersection = (start.z - (gridLocation.y * gridSpacing.z)) * -direction.z; |
| distBetweenZIntersections = -gridSpacing.z * ooDirection.z; |
| stepZDirection = -1; |
| } else { |
| distToNextZIntersection = Float.MAX_VALUE; |
| distBetweenZIntersections = Float.MAX_VALUE; |
| stepZDirection = 0; |
| } |
| |
| // Reset some variables |
| rayLocation.set(start); |
| rayLength = 0.0f; |
| stepDirection = Direction.None; |
| } |
| |
| public void next() { |
| // Walk us to our next location based on distances to next X or Z grid |
| // line. |
| if (distToNextXIntersection < distToNextZIntersection) { |
| rayLength = distToNextXIntersection; |
| gridLocation.x += stepXDirection; |
| distToNextXIntersection += distBetweenXIntersections; |
| switch (stepXDirection) { |
| case -1: |
| stepDirection = Direction.NegativeX; |
| break; |
| case 0: |
| stepDirection = Direction.None; |
| break; |
| case 1: |
| stepDirection = Direction.PositiveX; |
| break; |
| } |
| } else { |
| rayLength = distToNextZIntersection; |
| gridLocation.y += stepZDirection; |
| distToNextZIntersection += distBetweenZIntersections; |
| switch (stepZDirection) { |
| case -1: |
| stepDirection = Direction.NegativeZ; |
| break; |
| case 0: |
| stepDirection = Direction.None; |
| break; |
| case 1: |
| stepDirection = Direction.PositiveZ; |
| break; |
| } |
| } |
| |
| rayLocation.set(walkRay.direction).multLocal(rayLength).addLocal(walkRay.origin); |
| } |
| |
| public Direction getLastStepDirection() { |
| return stepDirection; |
| } |
| |
| public boolean isRayPerpendicularToGrid() { |
| return stepXDirection == 0 && stepZDirection == 0; |
| } |
| |
| |
| public Vector2f getGridLocation() { |
| return gridLocation; |
| } |
| |
| public Vector3f getGridOrigin() { |
| return gridOrigin; |
| } |
| |
| public Vector3f getGridSpacing() { |
| return gridSpacing; |
| } |
| |
| |
| public void setGridLocation(Vector2f gridLocation) { |
| this.gridLocation = gridLocation; |
| } |
| |
| public void setGridOrigin(Vector3f gridOrigin) { |
| this.gridOrigin = gridOrigin; |
| } |
| |
| public void setGridSpacing(Vector3f gridSpacing) { |
| this.gridSpacing = gridSpacing; |
| } |
| } |