Make hit explosions more interesting

Author: swoolcock

osu.Game.Rulesets.Rush/UI/DefaultHitExplosion.cs

@@ -1,11 +1,15 @@
 // Copyright (c) Shane Woolcock. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
+using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
 using osu.Framework.Graphics.Sprites;
 using osu.Framework.Graphics.Textures;
+using osu.Framework.Utils;
 using osuTK;
 using osuTK.Graphics;
 
@@ -18,13 +22,12 @@ public class DefaultHitExplosion : CompositeDrawable
 
         public override bool RemoveWhenNotAlive => true;
 
-        public DefaultHitExplosion(Color4 explosionColour)
+        public DefaultHitExplosion(Color4 explosionColour, int sparkCount = 10, Color4? sparkColour = null)
         {
             Origin = Anchor.Centre;
 
             InternalChildren = new Drawable[]
             {
-                // TODO: flashbang
                 colouredExplosion = new Sprite
                 {
                     Anchor = Anchor.Centre,
@@ -38,7 +41,14 @@ public DefaultHitExplosion(Color4 explosionColour)
                     Origin = Anchor.Centre,
                     Scale = new Vector2(0.75f)
                 },
-                // TODO: small particles
+                new Sparks(sparkCount)
+                {
+                    Anchor = Anchor.Centre,
+                    Origin = Anchor.Centre,
+                    RelativeSizeAxes = Axes.Both,
+                    Size = new Vector2(2f),
+                    Colour = sparkColour ?? Color4.White
+                }
                 // TODO: stars
             };
         }
@@ -49,5 +59,53 @@ private void load(TextureStore store)
             colouredExplosion.Texture = store.Get("exp");
             whiteExplosion.Texture = store.Get("exp");
         }
+
+        protected class Sparks : CompositeDrawable
+        {
+            private const double average_duration = 1500f;
+
+            private readonly Random random = new Random();
+            private readonly Triangle[] triangles;
+
+            private double randomDirection(int index, int max)
+            {
+                var offset = random.NextDouble() * 2f / max;
+                return (double)index / max + offset;
+            }
+
+            public Sparks(int sparkCount)
+            {
+                Origin = Anchor.Centre;
+                Anchor = Anchor.Centre;
+                RelativeSizeAxes = Axes.Both;
+
+                triangles = Enumerable.Range(0, sparkCount).Select(i => new Triangle
+                {
+                    Origin = Anchor.Centre,
+                    Anchor = Anchor.Centre,
+                    Size = new Vector2(5f, 10f),
+                    Rotation = (float)(randomDirection(i, sparkCount) * 360),
+                }).ToArray();
+
+                InternalChildren = triangles;
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                foreach (var triangle in triangles)
+                {
+                    var scale = 0.8f + random.NextDouble() * 0.2f;
+                    var duration = average_duration * (0.8f + random.NextDouble() * 0.4f);
+                    var radians = MathUtils.DegreesToRadians(triangle.Rotation + 90);
+                    var distance = DrawWidth * (0.8f + random.NextDouble() * 0.2f);
+                    var target = new Vector2(MathF.Cos(radians), MathF.Sin(radians)) * (float)distance;
+                    triangle.Scale = new Vector2((float)scale);
+                    triangle.MoveTo(target, duration, Easing.OutExpo);
+                    triangle.FadeOutFromOne(duration, Easing.InExpo);
+                }
+            }
+        }
     }
 }

osu.Game.Rulesets.Rush/UI/RushPlayfield.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Shane Woolcock. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
 using System.Diagnostics;
 using osu.Framework.Allocation;
 using osu.Framework.Extensions.Color4Extensions;
@@ -20,6 +21,8 @@ namespace osu.Game.Rulesets.Rush.UI
     [Cached]
     public class RushPlayfield : ScrollingPlayfield
     {
+        private readonly Random random = new Random();
+
         public const float DEFAULT_HEIGHT = 178;
         public const float HIT_TARGET_OFFSET = 120;
         public const float HIT_TARGET_SIZE = 100;
@@ -191,11 +194,16 @@ private void onNewResult(DrawableHitObject judgedObject, JudgementResult result)
                 case Orb _:
                     Debug.Assert(drawableLanedHit != null, nameof(drawableLanedHit) + " != null");
 
+                    // some random rotation and scale for variety
+                    var startScale = 0.9f + random.NextDouble() * 0.2f;
+                    var rotation = random.NextDouble() * 360;
                     var explosion = new DefaultHitExplosion(drawableLanedHit.LaneAccentColour)
                     {
                         Origin = Anchor.Centre,
                         Anchor = drawableLanedHit.LaneAnchor,
                         Size = new Vector2(200, 200),
+                        Scale = new Vector2((float)startScale),
+                        Rotation = (float)rotation
                     };
 
                     underEffectContainer.Add(explosion);