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Now that paths drive the scrolling of our view, we can go back to the

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simple line path calculations that don't suffer from the accumulated
rounding errors that our previous method did.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@1434 542714f4-19e9-0310-aa3c-eee0fc999fb1
This commit is contained in:
Michael Bayne
2002-06-11 00:03:30 +00:00
parent 0443a31294
commit cccd28ea9d
1 changed files with 18 additions and 53 deletions
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src/java/com/threerings/media/util/LinePath.java
+18 -53
View File
@@ -1,5 +1,5 @@
//
// $Id: LinePath.java,v 1.4 2002/05/31 22:14:44 mdb Exp $
// $Id: LinePath.java,v 1.5 2002/06/11 00:03:30 mdb Exp $
package com.threerings.media.util;
@@ -44,7 +44,6 @@ public class LinePath implements Path
_source = source;
_dest = dest;
_duration = duration;
_distance = (int)MathUtil.distance(_source, _dest);
}
// documentation inherited from interface
@@ -61,11 +60,8 @@ public class LinePath implements Path
// give the pable a chance to perform any starting antics
pable.pathBeginning();
// make a note of the time at which we expect to arrive
_arrivalTime = timestamp + _duration;
// pretend like we just moved the pathable
_lastMoveX = _lastMoveY = timestamp;
// make a note of when we started
_startStamp = timestamp;
// update our position to the start of the path
tick(pable, timestamp);
@@ -76,44 +72,26 @@ public class LinePath implements Path
{
// if we've blown past our arrival time, we need to get our bootay
// to the prearranged spot and get the hell out
if (timestamp >= _arrivalTime) {
if (timestamp >= _startStamp + _duration) {
pable.setLocation(_dest.x, _dest.y);
pable.pathCompleted();
return true;
}
// the number of milliseconds since we last moved (move delta)
float dtX = (float)(timestamp - _lastMoveX);
float dtY = (float)(timestamp - _lastMoveY);
// the number of milliseconds until we're expected to finish
float rtX = (float)(_arrivalTime - _lastMoveX);
float rtY = (float)(_arrivalTime - _lastMoveY);
// how many pixels we have left to go
int leftx = _dest.x - pable.getX(), lefty = _dest.y - pable.getY();
// determine where we should be along the path
float pct = (timestamp - _startStamp) / (float)_duration;
int travx = Math.round((_dest.x - _source.x) * pct);
int travy = Math.round((_dest.y - _source.y) * pct);
int nx = _source.x + travx, ny = _source.y + travy;
// we want to move the pathable by the remaining distance
// multiplied by the move delta divided by the remaining time and
// we update our last move stamps if there is movement to be had
// in either direction
int dx = Math.round((float)(leftx * dtX) / rtX);
if (dx != 0) {
_lastMoveX = timestamp;
}
int dy = Math.round((float)(lefty * dtY) / rtY);
if (dy != 0) {
_lastMoveY = timestamp;
}
// Log.info("Updated pathable [duration=" + _duration +
// ", dist=" + _distance +
// ", dtX=" + dtX + ", rtX=" + rtX +
// ", dtY=" + dtY + ", rtY=" + rtY +
// ", leftx=" + leftx + ", lefty=" + lefty +
// ", dx=" + dx + ", dy=" + dy + "].");
// Log.info("Updated pathable [duration=" + _duration + ", pct=" + pct +
// ", travx=" + travx + ", travy=" + travy +
// ", newx=" + nx + ", newy=" + ny + "].");
// only update the pathable's location if it actually moved
if (dx != 0 || dy != 0) {
pable.setLocation(pable.getX() + dx, pable.getY() + dy);
int cx = pable.getX(), cy = pable.getY();
if (cx != nx || cy != ny) {
pable.setLocation(nx, ny);
return true;
}
@@ -123,9 +101,7 @@ public class LinePath implements Path
// documentation inherited
public void fastForward (long timeDelta)
{
_arrivalTime += timeDelta;
_lastMoveX += timeDelta;
_lastMoveY += timeDelta;
_startStamp += timeDelta;
}
// documentation inherited
@@ -146,20 +122,9 @@ public class LinePath implements Path
/** Our source and destination points. */
protected Point _source, _dest;
/** The direct pixel distance along the path. */
protected int _distance;
/** The time at which we started along the path. */
protected long _startStamp;
/** The duration that we're to spend following the path. */
protected long _duration;
/** The time at which we expect to complete our path. */
protected long _arrivalTime;
/** The time at which we last actually moved the pathable in the x
* direction. */
protected long _lastMoveX;
/** The time at which we last actually moved the pathable in the y
* direction. */
protected long _lastMoveY;
}