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Do dat math!

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git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3612 542714f4-19e9-0310-aa3c-eee0fc999fb1
This commit is contained in:
Michael Bayne
2005-06-22 18:50:38 +00:00
parent 681561c4bf
commit dfa9216b89
2 changed files with 38 additions and 9 deletions
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src/java/com/threerings/jme/sprite/BallisticPath.java
+21
View File
@@ -21,6 +21,7 @@
package com.threerings.jme.sprite;
import com.jme.math.FastMath;
import com.jme.math.Vector3f;
/**
@@ -62,6 +63,26 @@ public class BallisticPath extends Path
}
}
/**
* Computes and returns the angle of elevation needed to launch a
* ballistic projectile at the specified velocity and have it travel
* the specified range (when it will once again reach the launch
* elevation).
*/
public static float computeElevation (float range, float vel, float accel)
{
return FastMath.asin(accel * range / (vel * vel)) / 2;
}
/**
* Computes and returns the flight time of a projectile launched at an
* angle previously computed with {@link #computeElevation}..
*/
public static float computeFlightTime (float range, float vel, float angle)
{
return range / (vel * FastMath.cos(angle));
}
protected Vector3f _curpos, _velocity, _accel;
protected float _duration, _accum;
protected Vector3f _temp = new Vector3f(0, 0, 0);
tests/src/java/com/threerings/jme/sprite/PathTest.java
+17 -9
View File
@@ -34,13 +34,15 @@ public class PathTest extends JmeApp
rotm.multLocal(_camera.getLeft());
_camera.update();
float range = 560, muzvel = 82;
Box box = new Box("box", new Vector3f(-1, -1, -1),
new Vector3f(1, 1, 1));
_geom.attachChild(box);
Box box2 = new Box("box2", new Vector3f(-1, -1, -1),
new Vector3f(1, 1, 1));
box2.setLocalTranslation(new Vector3f(560, 0, 0));
box2.setLocalTranslation(new Vector3f(range, 0, 0));
_geom.attachChild(box2);
Sphere ball = new Sphere("ball", 10, 10, 1);
@@ -52,19 +54,25 @@ public class PathTest extends JmeApp
// start with the "cannon" pointed along the x axis
Vector3f vel = new Vector3f(1, 0, 0);
// rotate it up (around the y axis) the necessary elevation
Quaternion rot = new Quaternion();
rot.fromAngleAxis(-FastMath.PI*27.35f/180f, new Vector3f(0, 1, 0));
// rot.fromAngleAxis(-FastMath.PI*62.65f/180f, new Vector3f(0, 1, 0));
float angle = BallisticPath.computeElevation(range, muzvel, -9.8f);
rot.fromAngleAxis(angle, new Vector3f(0, 1, 0));
rot.multLocal(vel);
// give the cannon a "muzzle velocity"
vel.multLocal(82f);
System.out.println("Start: " + start);
// give the cannon its muzzle velocity
vel.multLocal(muzvel);
float time = BallisticPath.computeFlightTime(range, muzvel, angle);
shot.move(new BallisticPath(shot, start, vel, GRAVITY, time));
System.out.println("Range: " + range);
System.out.println("Muzzle velocity: " + muzvel);
System.out.println("Angle: " + angle + " (" +
(angle * 180 / FastMath.PI) + ")");
System.out.println("Flight time: " + time);
System.out.println("Velocity: " + vel);
shot.move(new BallisticPath(shot, start, vel, GRAVITY, 7.7f));
// shot.move(new BallisticPath(shot, start, vel, GRAVITY, 15f));
}
public static void main (String[] args)