Corrected the particle paths, see #53

js/spin/model/ParticleRays.ts

@@ -3,6 +3,17 @@
 /**
  * ParticleRays contains the data for the particle ray paths in the UI.
  *
+ * All possible paths are indexed as such:
+ * 0 - Source to SG1
+ * 1 - SG1 to infinity (top)
+ * 2 - SG1 to infinity (bottom)
+ * 3 - SG1 to SG2
+ * 4 - SG2 to infinity (top)
+ * 5 - SG2 to infinity (bottom)
+ * 6 - SG2 to SG3
+ * 7 - SG3 to infinity (top)
+ * 8 - SG3 to infinity (bottom)
+ *
  * @author Agustín Vallejo
  */
 
@@ -63,28 +74,22 @@ export default class ParticleRays {
     this.updatedEmitter.emit();
   }
 
-  public updateFirstRay( rayPoints: Vector2[] ): void {
-    this.allPossiblePaths[ 0 ] = rayPoints;
-  }
-
   public assignRayToParticle( particle: ParticleWithSpinModel ): void {
     if ( this.isShortExperiment ) {
       particle.path = [
-        this.activePaths[ 0 ],
-        this.activePaths[ particle.secondSpinUp ? 1 : 2 ]
+        ...this.allPossiblePaths[ 0 ], // Source to SG1
+        ...this.allPossiblePaths[ particle.secondSpinUp ? 1 : 2 ] // SG1 to infinity
       ];
     }
     else {
       particle.path = [
-        this.activePaths[ 0 ],
-        this.activePaths[ particle.secondSpinUp ? 1 : 2 ],
-        this.activePaths[ 3 + ( particle.secondSpinUp ? 2 : 0 ) + ( particle.thirdSpinUp ? 1 : 0 ) ]
+        ...this.allPossiblePaths[ 0 ], // Source to SG1
+        ...this.allPossiblePaths[ particle.secondSpinUp ? 3 : 6 ], // SG1 to SG2
+        ...this.allPossiblePaths[ 4 + ( particle.secondSpinUp ? 0 : 3 ) + ( particle.thirdSpinUp ? 0 : 1 ) ]
       ];
     }
 
-    // Set the speed so it takes 1s to travel the first ray
-    particle.speed = this.activePaths[ 0 ][ 0 ].distance( this.activePaths[ 0 ][ 1 ] );
-
+    particle.updateSpeed();
   }
 
   public updateProbabilities( probabilities: number[] ): void {

js/spin/model/ParticleSourceModel.ts

@@ -56,6 +56,13 @@ export default class ParticleSourceModel {
     } );
 
   }
+
+  public reset(): void {
+    this.sourceModeProperty.reset();
+    this.positionProperty.reset();
+    this.currentlyShootingParticlesProperty.reset();
+    this.particleAmmountProperty.reset();
+  }
 }
 
 quantumMeasurement.register( 'ParticleSourceModel', ParticleSourceModel );

js/spin/model/ParticleWithSpinModel.ts

@@ -25,12 +25,15 @@ import Vector2 from '../../../../dot/js/Vector2.js';
 import Vector2Property from '../../../../dot/js/Vector2Property.js';
 import quantumMeasurement from '../../quantumMeasurement.js';
 
+// constants
+const SPEED_MULTIPLIER = 1.5;
+
 export class ParticleWithSpinModel {
 
   public lifetime = 0;
   public activeProperty: BooleanProperty;
 
-  public path: Vector2[][] = [];
+  public path: Vector2[] = [];
 
   // Spin values of the particle in the XZ plane along its lifetime
   public firstSpinVector = new Vector2( 0, 0 );
@@ -54,6 +57,14 @@ export class ParticleWithSpinModel {
     this.positionProperty = new Vector2Property( new Vector2( 0, 0 ) );
   }
 
+  /**
+   * Updates the speed of the particle based on the distance between the first two points of the path.
+   * When the multiplier is 1, it takes 1s to transverse from the emitting source to the first SG apparatus.
+   */
+  public updateSpeed(): void {
+    this.speed = SPEED_MULTIPLIER * this.path[ 0 ].distance( this.path[ 1 ] );
+  }
+
   public step( dt: number ): void {
     if ( this.activeProperty.value ) {
       this.lifetime += dt;
@@ -75,50 +86,41 @@ export class ParticleWithSpinModel {
    * t = 4 to t = 5: Traveling onwards from SG2 or SG3 -> Paths 3 - 6
    */
   public calculatePosition(): void {
-    // Travel from vector a to vector b based on speed and t
-    const travel = ( a: Vector2, b: Vector2, t: number ): Vector2 => {
+
+    // Travel until the final point, then stop
+    const clampTravel = ( a: Vector2, b: Vector2, t: number ): Vector2 => {
       const direction = b.minus( a ).normalized();
-      return a.plus( direction.times( this.speed * t ) );
+      const distance = this.speed * t;
+      return distance < a.distance( b ) ? a.plus( direction.times( distance ) ) : b;
     };
 
-    const fractionalLifetime = this.lifetime % 1;
-
-    switch( Math.floor( this.lifetime ) ) {
-      case 0:
-        // Between the first two points of the first path
-        this.positionProperty.value = travel( this.path[ 0 ][ 0 ], this.path[ 0 ][ 1 ], fractionalLifetime );
-        break;
-      case 1:
-        // In the middle of the SG1 apparatus
-        this.positionProperty.value = travel( this.path[ 0 ][ 1 ], this.path[ 1 ][ 0 ], 0.5 );
-        this.readyToBeMeasuredEmitter.emit();
-        break;
-      case 2:
-        // Along the second or third paths
-        this.positionProperty.value = travel( this.path[ 1 ][ 0 ], this.path[ 1 ][ 1 ], fractionalLifetime );
-        break;
-      case 3:
-        // Inside a SG2 or SG3 apparatus
-        if ( this.path.length > 3 ) {
-          this.positionProperty.value = travel( this.path[ 0 ][ 1 ], this.path[ 1 ][ 0 ], 0.5 );
-          this.readyToBeMeasuredEmitter.emit();
-        }
-        else {
-          this.positionProperty.value = travel( this.path[ 1 ][ 0 ], this.path[ 1 ][ 1 ], this.lifetime - 2 );
-        }
-        break;
-      default:
-        // Along the last paths
-        if ( this.path.length > 3 ) {
-          this.positionProperty.value = travel( this.path[ 2 ][ 0 ], this.path[ 2 ][ 1 ], this.lifetime - 4 );
+    // Similar to clampTravel but if it reached the end, move to the next pair of vectors until the end
+    const pathTravel = ( path: Vector2[], t: number ): Vector2 => {
+      let traveledTime = t;
+      let traveledDistance = this.speed * t;
+      let currentPosition = path[ 0 ];
+
+      for ( let i = 0; i < path.length - 1; i++ ) {
+        const start = path[ i ];
+        const end = path[ i + 1 ];
+        const segmentDistance = start.distance( end );
+
+        if ( traveledDistance < segmentDistance ) {
+          return clampTravel( start, end, traveledTime );
         }
         else {
-          this.positionProperty.value = travel( this.path[ 1 ][ 0 ], this.path[ 1 ][ 1 ], this.lifetime - 2 );
+          traveledTime -= segmentDistance / this.speed;
+          traveledDistance -= segmentDistance;
+          currentPosition = end;
         }
-        break;
-    }
+      }
+
+      return currentPosition;
+    };
+
+    // Travel along the path
+    this.positionProperty.value = pathTravel( this.path, this.lifetime );
 
-    console.log( this.positionProperty.value );
   }
 
   public reset(): void {

js/spin/model/SpinModel.ts

@@ -71,7 +71,7 @@ export default class SpinModel implements TModel {
         tandem: providedOptions.tandem.createTandem( 'blochSphere' )
       } );
 
-    const MAX_NUMBER_OF_SINGLE_PARTICLES = 10;
+    const MAX_NUMBER_OF_SINGLE_PARTICLES = 50;
 
     this.currentExperimentProperty = new Property<SpinExperiment>( SpinExperiment.EXPERIMENT_1 );
 
@@ -150,6 +150,8 @@ export default class SpinModel implements TModel {
     const SternGerlachs = [ this.firstSternGerlach, this.secondSternGerlach, this.thirdSternGerlach ];
 
     this.currentExperimentProperty.link( experiment => {
+      this.singleParticles.forEach( particle => particle.reset() );
+
       SternGerlachs.forEach( ( SternGerlach, index ) => {
         if ( experiment.experimentSetting.length > index ) {
           // TODO: Should visibility be only handled via the View? https://github.com/phetsims/quantum-preparement/issues/53
@@ -185,13 +187,16 @@ export default class SpinModel implements TModel {
             let upProbability = 1;
             upProbability = this.firstSternGerlach.prepare( this.spinStateProperty.value );
             particleToActivate.secondSpinUp = dotRandom.nextDouble() < upProbability;
-            if ( particleToActivate.secondSpinUp ) {
-              upProbability = this.secondSternGerlach.prepare( this.firstSternGerlach.isZOrientedProperty ? SpinDirection.Z_PLUS : SpinDirection.X_PLUS );
-              particleToActivate.thirdSpinUp = dotRandom.nextDouble() < upProbability;
-            }
-            else {
-              const upProbability = this.thirdSternGerlach.prepare( this.firstSternGerlach.isZOrientedProperty ? SpinDirection.Z_MINUS : null );
-              particleToActivate.thirdSpinUp = dotRandom.nextDouble() < upProbability;
+
+            if ( this.currentExperimentProperty.value.experimentSetting.length > 1 ) {
+              if ( particleToActivate.secondSpinUp ) {
+                upProbability = this.secondSternGerlach.prepare( this.firstSternGerlach.isZOrientedProperty.value ? SpinDirection.Z_PLUS : SpinDirection.X_PLUS );
+                particleToActivate.thirdSpinUp = dotRandom.nextDouble() < upProbability;
+              }
+              else {
+                const upProbability = this.thirdSternGerlach.prepare( this.firstSternGerlach.isZOrientedProperty.value ? SpinDirection.Z_MINUS : null );
+                particleToActivate.thirdSpinUp = dotRandom.nextDouble() < upProbability;
+              }
             }
 
             this.particleRays.assignRayToParticle( particleToActivate );
@@ -231,7 +236,13 @@ export default class SpinModel implements TModel {
    * Resets the model.
    */
   public reset(): void {
-    // TODO, see https://github.com/phetsims/quantum-preparement/issues/1
+    this.singleParticles.forEach( particle => particle.reset() );
+    this.currentExperimentProperty.reset();
+    this.spinStateProperty.reset();
+    this.firstSternGerlach.reset();
+    this.secondSternGerlach.reset();
+    this.thirdSternGerlach.reset();
+    this.particleSourceModel.reset();
   }
 
   /**

js/spin/view/SpinMeasurementArea.ts

@@ -9,6 +9,7 @@
 
 import Bounds2 from '../../../../dot/js/Bounds2.js';
 import Vector2 from '../../../../dot/js/Vector2.js';
+import { Shape } from '../../../../kite/js/imports.js';
 import ModelViewTransform2 from '../../../../phetcommon/js/view/ModelViewTransform2.js';
 import PhetFont from '../../../../scenery-phet/js/PhetFont.js';
 import { Node, Text, VBox } from '../../../../scenery/js/imports.js';
@@ -61,14 +62,13 @@ export default class SpinMeasurementArea extends VBox {
         particleSourceNode,
         firstSternGerlachNode,
         secondSternGerlachNode,
-        thirdSternGerlachNode,
-        particleRayPath
+        thirdSternGerlachNode
       ]
     } );
 
-    // experimentAreaNode.clipArea = Shape.bounds( experimentAreaNode.localBounds );
+    experimentAreaNode.clipArea = Shape.bounds( experimentAreaNode.localBounds );
 
-    // experimentAreaNode.insertChild( 0, particleRayPath );
+    experimentAreaNode.insertChild( 0, particleRayPath );
 
     super( {
       children: [
@@ -81,7 +81,7 @@ export default class SpinMeasurementArea extends VBox {
 
       ],
       spacing: 20,
-      margin: 20
+      margin: 30
     } );
 
   }

js/spin/view/SpinScreenView.ts

@@ -18,7 +18,7 @@ import SpinStatePreparationArea from './SpinStatePreparationArea.js';
 
 export default class SpinScreenView extends QuantumMeasurementScreenView {
 
-  public constructor( model: SpinModel, tandem: Tandem ) {
+  public constructor( public readonly model: SpinModel, tandem: Tandem ) {
 
     super( {
       initialMockupOpacity: 0,
@@ -41,7 +41,7 @@ export default class SpinScreenView extends QuantumMeasurementScreenView {
     this.addChild( dividingLine );
 
     const spinMeasurementArea = new SpinMeasurementArea( model, this, this.layoutBounds, tandem.createTandem( 'spinMeasurementArea' ) );
-    spinMeasurementArea.centerX = 2 * dividingLineX;
+    spinMeasurementArea.left = dividingLineX;
     this.addChild( spinMeasurementArea );
 
     // TODO: This is a temporary workaround to make the mockup opacity work. We need to refactor this to use the mockup https://github.com/phetsims/quantum-measurement/issues/53
@@ -54,6 +54,7 @@ export default class SpinScreenView extends QuantumMeasurementScreenView {
   }
 
   public override reset(): void {
+    this.model.reset();
     super.reset();
   }
 }