Show apex as green dot, see #132

phetsims · Aug 10, 2017 · 46be1cb · 46be1cb
1 parent 9a67d72
commit 46be1cb
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Showing 3 changed files with 45 additions and 3 deletions.
diff --git a/js/common/model/Tracer.js b/js/common/model/Tracer.js
@@ -69,7 +69,7 @@ define( function( require ) {
         var currentTrajectory = this.trajectories.get( i );
         var point = currentTrajectory.getNearestPoint( this.positionProperty.get().x, this.positionProperty.get().y );
         var pointIsReadable = point &&
-          ( point.position.y === 0 || Util.toFixedNumber( point.time * 1000, 0 ) % TIME_PER_SHOWN_DOT === 0 );
+          ( point.apex || point.position.y === 0 || Util.toFixedNumber( point.time * 1000, 0 ) % TIME_PER_SHOWN_DOT === 0 );
         if ( pointIsReadable && point.position.distance( this.positionProperty.get() ) <= SENSING_RADIUS ) {
           this.dataPointProperty.set( point );
           return;
@@ -88,7 +88,7 @@ define( function( require ) {
 
       // point can be read by tracer if it exists, it is on the ground, or it is the right timestep
       var pointIsReadable = point &&
-        ( point.position.y === 0 || Util.toFixedNumber( point.time * 1000, 0 ) % TIME_PER_SHOWN_DOT === 0 );
+        ( point.apex || point.position.y === 0 || Util.toFixedNumber( point.time * 1000, 0 ) % TIME_PER_SHOWN_DOT === 0 );
       if ( pointIsReadable && point.position.distance( this.positionProperty.get() ) <= SENSING_RADIUS ) {
         this.dataPointProperty.set( point );
       }

diff --git a/js/common/model/Trajectory.js b/js/common/model/Trajectory.js
@@ -20,6 +20,7 @@ define( function( require ) {
   var NumberProperty = require( 'AXON/NumberProperty' );
   var ObservableArray = require( 'AXON/ObservableArray' );
   var Vector2 = require( 'DOT/Vector2' );
+  var Util = require( 'DOT/Util' );
 
   /**
    * @param {ProjectileMotionModel} model
@@ -157,6 +158,35 @@ define( function( require ) {
         var gravity = this.projectileMotionModel.gravityProperty.get();
 
         var newDragForce = Vector2.dirtyFromPool().set( newVelocity ).multiplyScalar( 0.5 * airDensity * area * this.dragCoefficient * newVelocity.magnitude() );
+
+        if ( previousPoint.velocity.y >= 0 && newVelocity.y < 0 ) { // passed apex
+          var dtToApex = Util.linear( previousPoint.velocity.y, newVelocity.y, 0, dt, 0 );
+          var apexX = Util.linear( 0, dt, previousPoint.position.x, newX, dtToApex );
+          var apexY = Util.linear( 0, dt, previousPoint.position.y, newY, dtToApex );
+          var apexVelocityX = Util.linear( 0, dt, previousPoint.velocity.x, newVelocity.x, dtToApex );
+          var apexVelocityY = Util.linear( 0, dt, previousPoint.velocity.y, newVelocity.y, dtToApex );
+          var apexDragX = Util.linear( 0, dt, previousPoint.dragForce.x, newDragForce.x, dtToApex );
+          var apexDragY = Util.linear( 0, dt, previousPoint.dragForce.y, newDragForce.y, dtToApex );
+
+          var apexPoint = new DataPoint(
+            previousPoint.time + dtToApex,
+            Vector2.createFromPool( apexX, apexY ),
+            airDensity,
+            Vector2.createFromPool( apexVelocityX, apexVelocityY ), // velocity
+            Vector2.createFromPool( -apexDragX / this.mass, -gravity - apexDragY / this.mass ), // acceleration
+            Vector2.createFromPool( apexDragX, apexDragY ), // drag force
+            -gravity * this.mass
+          );
+
+          // add this special property to just the apex point collected for a trajectory
+          apexPoint.apex = true;
+
+          // push it
+          this.dataPoints.push( apexPoint );
+          this.projectileMotionModel.tracer.updateDataIfWithinRange( apexPoint );
+          this.projectileMotionModel.updateDavidIfWithinRange( apexPoint.position );
+
+        }
 
         // Has reached ground or below
         if ( newY <= 0 ) {

diff --git a/js/common/view/TrajectoryNode.js b/js/common/view/TrajectoryNode.js
@@ -20,6 +20,7 @@ define( function( require ) {
   var Shape = require( 'KITE/Shape' );
   var Vector2 = require( 'DOT/Vector2' );
   var Util = require( 'DOT/Util' );
+  var Circle = require( 'SCENERY/nodes/Circle' );
 
   // constants
   var MAX_TRAJECTORY_COUNT = ProjectileMotionConstants.MAX_NUMBER_OF_TRAJECTORIES;
@@ -35,6 +36,8 @@ define( function( require ) {
   var DOTS_MAX_OPACITY = 0.5;
   var TIME_PER_SHOWN_DOT = ProjectileMotionConstants.TIME_PER_SHOWN_DOT; // milliseconds
 
+  var DOT_GREEN = 'rgb( 50, 255, 50 )';
+
   /**
    * @param {VectorVisibilityProperties} vectorVisibilityProperties - Properties that determine which vectors are shown,
    * only needed to pass down to ProjectileNode
@@ -64,7 +67,10 @@ define( function( require ) {
 
     this.addChild( projectileObjectViewsLayer );
     this.addChild( pathsLayer );
-    this.addChild( dotsPath );
+
+    var dotsLayer = new Node();
+    dotsLayer.addChild( dotsPath );
+    this.addChild( dotsLayer );
     this.addChild( projectileNodesLayer );
 
     var viewLastPosition = null;
@@ -94,6 +100,12 @@ define( function( require ) {
         dotsShape.moveTo( viewAddedPosition.x + DOT_RADIUS, viewAddedPosition.y )
           .circle( viewAddedPosition.x, viewAddedPosition.y, DOT_RADIUS );
       }
+
+      // draw green dot if apex
+      if ( addedPoint.apex ) {
+        var apexDot = new Circle( DOT_RADIUS, { x: viewAddedPosition.x, y: viewAddedPosition.y, fill: DOT_GREEN, stroke: DOT_GREEN } );
+        dotsLayer.addChild( apexDot );
+      }
     }
 
     // view listens to whether a datapoint has been added in the model