Need to fix drag and friction algorithms

Author: dacuster

Game Physics/Assets/Scenes/Scene_Main.unity

@@ -444,14 +444,14 @@ MonoBehaviour:
   staticFrictionCoefficient: 0.6
   staticFrictionNormal: {x: 1, y: 0}
   staticFrictionOpposingForce: {x: -1, y: 0}
-  slidingNormalForce: {x: 1, y: 0}
+  slidingNormalForce: {x: 1, y: -0.5}
   gravityActive: 1
   normalActive: 1
   slidingActive: 0
   staticFrictionActive: 0
   kinematicFrictionActive: 0
   dragActive: 0
-  springActive: 0
+  springActive: 1
   dampingSpringActive: 0
 --- !u!65 &1373288496
 BoxCollider:

Game Physics/Assets/Scripts/ForceGenerator.cs

@@ -38,14 +38,15 @@ public static Vector2 GenerateForce_Friction_Static(Vector2 _forceNormal, Vector
         float max = _frictionCoefficient_Static * _forceNormal.magnitude;
 
         Vector2 force = _frictionCoefficient_Static * _forceNormal;
+        float mag = _forceOpposing.magnitude;
 
-        if (_forceOpposing.magnitude > max)
+        if (mag > max)
         {
-            force -= _forceOpposing;
+            force = -_forceOpposing;
         }
         else
         {
-            force = -_frictionCoefficient_Static * _forceNormal;
+            force = -_forceOpposing * max / mag;
         }
 
         return force;
@@ -55,7 +56,7 @@ public static Vector2 GenerateForce_Friction_Kinetic(Vector2 f_normal, Vector2 p
     {
         // f_friction_k = -coeff*|f_normal| * unit(vel)
 
-        Vector2 force = -frictionCoefficient_kinetic * f_normal.magnitude * particleVelocity;
+        Vector2 force = -frictionCoefficient_kinetic * f_normal.magnitude * particleVelocity.normalized;
 
         return force;
     }
@@ -64,7 +65,9 @@ public static Vector2 GenerateForce_Drag(Vector2 particleVelocity, Vector2 fluid
     {
         // f_drag = (p * u^2 * area * coeff)/2
 
-        Vector2 force = (particleVelocity - fluidVelocity) * (fluidDensity * particleVelocity.magnitude * particleVelocity.magnitude * objectArea_crossSection * objectDragCoefficient * 0.5f);
+        Vector2 diff = particleVelocity - fluidVelocity;
+
+        Vector2 force = diff * diff.magnitude * (fluidDensity * objectArea_crossSection * objectDragCoefficient * 0.5f);
 
         return force;
     }
@@ -77,11 +80,13 @@ public static Vector2 GenerateForce_Spring(Vector2 particlePosition, Vector2 anc
         // Calculate relative position of the particle to the anchor.
         Vector2 position = particlePosition - anchorPosition;
 
+        float springLength = position.magnitude;
+
         // Generate the force.
-        float force = -springStiffnessCoefficient * (position.magnitude - springRestingLength);
+        float force = -springStiffnessCoefficient * (springLength - springRestingLength);
 
         // Return the force at the current position.
-        return position * force;
+        return position * force / springLength;
     }
     public static Vector2 GenerateForce_Spring_Damping(Vector2 particlePosition, Vector2 anchorPosition, float springRestingLength, float springStiffnessCoefficient, float springDamping, float springConstant, Vector2 particleVelocity)
     {