com.threerings.media.util.LineSegmentPath Maven / Gradle / Ivy
//
// Nenya library - tools for developing networked games
// Copyright (C) 2002-2012 Three Rings Design, Inc., All Rights Reserved
// https://github.com/threerings/nenya
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package com.threerings.media.util;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Point;
import com.google.common.collect.Lists;
import com.samskivert.util.StringUtil;
import com.threerings.util.DirectionCodes;
import com.threerings.util.DirectionUtil;
import static com.threerings.media.Log.log;
/**
* The line segment path is used to cause a pathable to follow a path that is made up of a
* sequence of line segments. There must be at least two nodes in any worthwhile path. The
* direction of the first node in the path is meaningless since the pathable begins at that node
* and will therefore never be heading towards it.
*/
public class LineSegmentPath
implements DirectionCodes, Path
{
/**
* Constructs an empty line segment path.
*/
public LineSegmentPath ()
{
}
/**
* Constructs a line segment path that consists of a single segment connecting the point
* (x1, y1) with (x2, y2). The orientation for the first node is set
* arbitrarily and the second node is oriented based on the vector between the two nodes (in
* top-down coordinates).
*/
public LineSegmentPath (int x1, int y1, int x2, int y2)
{
addNode(x1, y1, NORTH);
Point p1 = new Point(x1, y1), p2 = new Point(x2, y2);
int dir = DirectionUtil.getDirection(p1, p2);
addNode(x2, y2, dir);
}
/**
* Construct a line segment path between the two nodes with the specified direction.
*/
public LineSegmentPath (Point p1, Point p2, int dir)
{
addNode(p1.x, p1.y, NORTH);
addNode(p2.x, p2.y, dir);
}
/**
* Constructs a line segment path with the specified list of points. An arbitrary direction
* will be assigned to the starting node.
*/
public LineSegmentPath (List points)
{
createPath(points);
}
/**
* Returns the orientation the sprite will face at the end of the path.
*/
public int getFinalOrientation ()
{
return (_nodes.size() == 0) ? NORTH : _nodes.get(_nodes.size()-1).dir;
}
/**
* Add a node to the path with the specified destination point and facing direction.
*
* @param x the x-position.
* @param y the y-position.
* @param dir the facing direction.
*/
public void addNode (int x, int y, int dir)
{
_nodes.add(new PathNode(x, y, dir));
}
/**
* Return the requested node index in the path, or null if no such index exists.
*
* @param idx the node index.
*
* @return the path node.
*/
public PathNode getNode (int idx)
{
return _nodes.get(idx);
}
/**
* Return the number of nodes in the path.
*/
public int size ()
{
return _nodes.size();
}
/**
* Sets the velocity of this pathable in pixels per millisecond. The velocity is measured as
* pixels traversed along the path that the pathable is traveling rather than in the x or y
* directions individually. Note that the pathable velocity should not be changed while a path
* is being traversed; doing so may result in the pathable position changing unexpectedly.
*
* @param velocity the pathable velocity in pixels per millisecond.
*/
public void setVelocity (float velocity)
{
_vel = velocity;
}
/**
* Computes the velocity at which the pathable will need to travel along this path such that
* it will arrive at the destination in approximately the specified number of milliseconds.
* Efforts are taken to get the pathable there as close to the desired time as possible, but
* framerate variation may prevent it from arriving exactly on time.
*/
public void setDuration (long millis)
{
// if we have only zero or one nodes, we don't have enough
// information to compute our velocity
int ncount = _nodes.size();
if (ncount < 2) {
log.warning("Requested to set duration of bogus path",
"path", this, "duration", millis);
return;
}
// compute the total distance along our path
float distance = 0;
PathNode start = _nodes.get(0);
for (int ii = 1; ii < ncount; ii++) {
PathNode end = _nodes.get(ii);
distance += MathUtil.distance(start.loc.x, start.loc.y, end.loc.x, end.loc.y);
start = end;
}
// set the velocity accordingly
setVelocity(distance/millis);
}
// documentation inherited
public void init (Pathable pable, long timestamp)
{
// give the pathable a chance to perform any starting antics
pable.pathBeginning();
// if we have only one node then let the pathable know that we're done straight away
if (size() < 2) {
// move the pathable to the location specified by the first
// node (assuming we have a first node)
if (size() == 1) {
PathNode node = _nodes.get(0);
pable.setLocation(node.loc.x, node.loc.y);
}
// and let the pathable know that we're done
pable.pathCompleted(timestamp);
return;
}
// and an enumeration of the path nodes
_niter = _nodes.iterator();
// pretend like we were previously heading to our starting position
_dest = getNextNode();
// begin traversing the path
headToNextNode(pable, timestamp, timestamp);
}
// documentation inherited
public boolean tick (Pathable pable, long timestamp)
{
// figure out how far along this segment we should be
long msecs = timestamp - _nodestamp;
float travpix = msecs * _vel;
float pctdone = travpix / _seglength;
// if we've moved beyond the end of the path, we need to adjust
// the timestamp to determine how much time we used getting to the
// end of this node, then move to the next one
if (pctdone >= 1.0) {
long used = (long)(_seglength / _vel);
return headToNextNode(pable, _nodestamp + used, timestamp);
}
// otherwise we position the pathable along the path
int ox = pable.getX();
int oy = pable.getY();
int nx = _src.loc.x + (int)((_dest.loc.x - _src.loc.x) * pctdone);
int ny = _src.loc.y + (int)((_dest.loc.y - _src.loc.y) * pctdone);
// Log.info("Moving pathable [msecs=" + msecs + ", pctdone=" + pctdone +
// ", travpix=" + travpix + ", seglength=" + _seglength +
// ", dx=" + (nx-ox) + ", dy=" + (ny-oy) + "].");
// only update the pathable's location if it actually moved
if (ox != nx || oy != ny) {
pable.setLocation(nx, ny);
return true;
}
return false;
}
// documentation inherited
public void fastForward (long timeDelta)
{
_nodestamp += timeDelta;
}
// documentation inherited from interface
public void wasRemoved (Pathable pable)
{
// nothing doing
}
/**
* Place the pathable moving along the path at the end of the previous path node, face it
* appropriately for the next node, and start it on its way. Returns whether the pathable
* position moved.
*/
protected boolean headToNextNode (Pathable pable, long startstamp, long now)
{
if (_niter == null) {
throw new IllegalStateException("headToNextNode() called before init()");
}
// check to see if we've completed our path
if (!_niter.hasNext()) {
// move the pathable to the location of our last destination
pable.setLocation(_dest.loc.x, _dest.loc.y);
pable.pathCompleted(now);
return true;
}
// our previous destination is now our source
_src = _dest;
// pop the next node off the path
_dest = getNextNode();
// adjust the pathable's orientation
if (_dest.dir != NONE) {
pable.setOrientation(_dest.dir);
}
// make a note of when we started traversing this node
_nodestamp = startstamp;
// figure out the distance from source to destination
_seglength = MathUtil.distance(
_src.loc.x, _src.loc.y, _dest.loc.x, _dest.loc.y);
// if we're already there (the segment length is zero), we skip to
// the next segment
if (_seglength == 0) {
return headToNextNode(pable, startstamp, now);
}
// now update the pathable's position based on our progress thus far
return tick(pable, now);
}
// documentation inherited
public void paint (Graphics2D gfx)
{
gfx.setColor(Color.red);
Point prev = null;
int size = size();
for (int ii = 0; ii < size; ii++) {
PathNode n = getNode(ii);
if (prev != null) {
gfx.drawLine(prev.x, prev.y, n.loc.x, n.loc.y);
}
prev = n.loc;
}
}
@Override
public String toString ()
{
return StringUtil.toString(_nodes.iterator());
}
/**
* Populate the path with the path nodes that lead the pathable from its starting position to
* the given destination coordinates following the given list of screen coordinates.
*/
protected void createPath (List points)
{
Point last = null;
int size = points.size();
for (int ii = 0; ii < size; ii++) {
Point p = points.get(ii);
int dir = (ii == 0) ? NORTH : DirectionUtil.getDirection(last, p);
addNode(p.x, p.y, dir);
last = p;
}
}
/**
* Gets the next node in the path.
*/
protected PathNode getNextNode ()
{
return _niter.next();
}
/** The nodes that make up the path. */
protected ArrayList _nodes = Lists.newArrayList();
/** We use this when moving along this path. */
protected Iterator _niter;
/** When moving, the pathable's source path node. */
protected PathNode _src;
/** When moving, the pathable's destination path node. */
protected PathNode _dest;
/** The time at which we started traversing the current node. */
protected long _nodestamp;
/** The length in pixels of the current path segment. */
protected float _seglength;
/** The path velocity in pixels per millisecond. */
protected float _vel = DEFAULT_VELOCITY;
/** When moving, the pathable position including fractional pixels. */
protected float _movex, _movey;
/** When moving, the distance to move on each axis per tick. */
protected float _incx, _incy;
/** The distance to move on the straight path line per tick. */
protected float _fracx, _fracy;
/** Default pathable velocity. */
protected static final float DEFAULT_VELOCITY = 200f/1000f;
}
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