Simple particle interaction

Main.cs

@@ -1,15 +1,20 @@
 using System.Collections.Generic;
+using System.Linq;
 using Godot;
 
 public class Main : Node2D
 {
+    private const int ParticleScreenPadding = 16;
+
     private readonly List<ParticleType> _particleTypes = new List<ParticleType>();
+    private List<Particle> _particles;
 
     public override void _Ready()
     {
         GD.Randomize();
-        InitializeParticleTypes(5);
+        InitializeParticleTypes(10);
-        InitializeParticles(50);
+        InitializeParticles(200);
+        _particles = GetNode<Node2D>("Particles").GetChildren().Cast<Particle>().ToList();
     }
 
     public override void _Process(float delta)
@@ -18,6 +23,11 @@ public class Main : Node2D
         if (Input.IsActionJustPressed("reset")) GetTree().ReloadCurrentScene();
     }
 
+    public override void _PhysicsProcess(float delta)
+    {
+        UpdateParticles();
+    }
+
     private void InitializeParticleTypes(int nTypes)
     {
         for (var i = 0; i < nTypes; i++)
@@ -28,6 +38,10 @@ public class Main : Node2D
             };
             _particleTypes.Add(type);
         }
+
+        foreach (var type1 in _particleTypes)
+        foreach (var type2 in _particleTypes)
+            type1.AddRelationship(type2, 20, (float) GD.RandRange(25, 60), (float) GD.RandRange(-0.33, 0.35));
     }
 
     private void InitializeParticles(int nParticles)
@@ -50,10 +64,58 @@ public class Main : Node2D
 
     private Vector2 GetRandomParticlePosition()
     {
-        const int padding = 32;
         var viewportRect = GetViewportRect();
-        var position = new Vector2((float) GD.RandRange(padding, viewportRect.Size.x - padding),
+        var position = new Vector2(
-            (float) GD.RandRange(padding, viewportRect.Size.y - padding));
+            (float) GD.RandRange(ParticleScreenPadding, viewportRect.Size.x - ParticleScreenPadding),
+            (float) GD.RandRange(ParticleScreenPadding, viewportRect.Size.y - ParticleScreenPadding));
         return position;
     }
+
+    private void UpdateParticles()
+    {
+        var viewportRect = GetViewportRect();
+        foreach (var p1 in _particles)
+        {
+            foreach (var p2 in _particles)
+            {
+                if (p1 == p2)
+                    continue;
+                var distance = p1.Position.DistanceTo(p2.Position);
+                if (distance > 60f)
+                    continue;
+                var direction = p1.Position.DirectionTo(p2.Position);
+
+                // collision force
+                if (distance < 20)
+                {
+                    const float collisionStretch = 1f;
+                    const float collisionOffset = 13f;
+                    const float collisionFlatten = 1f;
+                    var rawCollisionForce = -Mathf.Pow(Mathf.E, -(collisionStretch * distance - collisionOffset)) /
+                                            collisionFlatten;
+                    var clampedCollisionForce = Mathf.Clamp(rawCollisionForce, -1f, 1f);
+                    p1.Velocity += direction * clampedCollisionForce;
+                }
+                // particle relationship force
+
+                var props = p1.Type.GetRelationship(p2.Type);
+                if (props.Force != 0f && distance >= props.MinRadius && distance <= props.MaxRadius)
+                {
+                    var slope = props.Force / ((props.MaxRadius - props.MinRadius) / 2f);
+                    var rawParticleForce = -slope * Mathf.Abs(distance - (props.MinRadius + props.MaxRadius) / 2f) +
+                                           props.Force;
+                    p1.Velocity += direction * rawParticleForce;
+                }
+
+                p1.Velocity = p1.Velocity.Clamped(3f);
+            }
+
+            var position = p1.Position;
+            position += p1.Velocity;
+            p1.Velocity *= 0.95f;
+            position.x = Mathf.Clamp(position.x, ParticleScreenPadding, viewportRect.Size.x - ParticleScreenPadding);
+            position.y = Mathf.Clamp(position.y, ParticleScreenPadding, viewportRect.Size.y - ParticleScreenPadding);
+            p1.Position = position;
+        }
+    }
 }

Particle.cs

@@ -5,6 +5,8 @@ public class Particle : Node2D
     private Sprite _spriteNode;
     private ParticleType _type;
 
+    public Vector2 Velocity { get; set; }
+
     public ParticleType Type
     {
         get => _type;

Particle.tscn

@@ -7,4 +7,5 @@
 script = ExtResource( 2 )
 
 [node name="Sprite" type="Sprite" parent="."]
+scale = Vector2( 0.25, 0.25 )
 texture = ExtResource( 1 )

ParticleType.cs

@@ -17,11 +17,11 @@ public struct ParticleRelationshipProps
 
 public class ParticleType
 {
-    private float _hue;
-
     private readonly Dictionary<ParticleType, ParticleRelationshipProps> _particleRelationships =
         new Dictionary<ParticleType, ParticleRelationshipProps>();
 
+    private float _hue;
+
     public float Hue
     {
         get => _hue;
@@ -35,4 +35,9 @@ public class ParticleType
         var props = new ParticleRelationshipProps(minRadius, maxRadius, force);
         _particleRelationships[type] = props;
     }
+
+    public ParticleRelationshipProps GetRelationship(ParticleType type)
+    {
+        return _particleRelationships[type];
+    }
 }

Particles.csproj

@@ -1,5 +1,7 @@
 <Project Sdk="Godot.NET.Sdk/3.3.0">
     <PropertyGroup>
         <TargetFramework>net472</TargetFramework>
+        <Configurations>Debug;ExportDebug;ExportRelease;Release</Configurations>
+        <Platforms>AnyCPU</Platforms>
     </PropertyGroup>
 </Project>

Particles.sln

@@ -7,13 +7,16 @@ Global
 	Debug|Any CPU = Debug|Any CPU
 	ExportDebug|Any CPU = ExportDebug|Any CPU
 	ExportRelease|Any CPU = ExportRelease|Any CPU
+		Release|Any CPU = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.ExportDebug|Any CPU.ActiveCfg = ExportDebug|Any CPU
 		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.ExportDebug|Any CPU.Build.0 = ExportDebug|Any CPU
-		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.ExportRelease|Any CPU.ActiveCfg = ExportRelease|Any CPU
+		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.ExportRelease|Any CPU.ActiveCfg = Debug|Any CPU
-		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.ExportRelease|Any CPU.Build.0 = ExportRelease|Any CPU
+		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.ExportRelease|Any CPU.Build.0 = Debug|Any CPU
+		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E15A1F42-C497-4EDE-8944-84CB055B33CB}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

project.godot

@@ -16,10 +16,8 @@ config/icon="res://icon.png"
 
 [display]
 
-window/size/width=1920
+window/size/width=1600
-window/size/height=1080
+window/size/height=900
-window/size/resizable=false
-window/size/borderless=true
 
 [input]