Merge pull request #21242 from EVAST9919/triangles-fix

Triangles background improvements

osu.Game.Tests/Visual/Background/TestSceneTrianglesBackground.cs

@@ -0,0 +1,40 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Game.Graphics.Backgrounds;
+using osu.Framework.Graphics;
+using osuTK.Graphics;
+using osu.Framework.Graphics.Shapes;
+
+namespace osu.Game.Tests.Visual.Background
+{
+    public class TestSceneTrianglesBackground : OsuTestScene
+    {
+        private readonly Triangles triangles;
+
+        public TestSceneTrianglesBackground()
+        {
+            Children = new Drawable[]
+            {
+                new Box
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    Colour = Color4.Black
+                },
+                triangles = new Triangles
+                {
+                    RelativeSizeAxes = Axes.Both,
+                    ColourLight = Color4.White,
+                    ColourDark = Color4.Gray
+                }
+            };
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            AddSliderStep("Triangle scale", 0f, 10f, 1f, s => triangles.TriangleScale = s);
+        }
+    }
+}

osu.Game/Graphics/Backgrounds/Triangles.cs

@@ -17,6 +17,7 @@
 using osu.Framework.Graphics.Rendering;
 using osu.Framework.Graphics.Rendering.Vertices;
 using osu.Framework.Lists;
+using osu.Framework.Bindables;
 
 namespace osu.Game.Graphics.Backgrounds
 {
@@ -25,6 +26,11 @@ public class Triangles : Drawable
         private const float triangle_size = 100;
         private const float base_velocity = 50;
 
+        /// <summary>
+        /// sqrt(3) / 2
+        /// </summary>
+        private const float equilateral_triangle_ratio = 0.866f;
+
         /// <summary>
         /// How many screen-space pixels are smoothed over.
         /// Same behavior as Sprite's EdgeSmoothness.
@@ -69,7 +75,13 @@ public Color4 ColourDark
         /// </summary>
         protected virtual float SpawnRatio => 1;
 
-        private float triangleScale = 1;
+        private readonly BindableFloat triangleScale = new BindableFloat(1f);
+
+        public float TriangleScale
+        {
+            get => triangleScale.Value;
+            set => triangleScale.Value = value;
+        }
 
         /// <summary>
         /// Whether we should drop-off alpha values of triangles more quickly to improve
@@ -109,24 +121,7 @@ private void load(IRenderer renderer, ShaderManager shaders)
         protected override void LoadComplete()
         {
             base.LoadComplete();
-            addTriangles(true);
-        }
-
-        public float TriangleScale
-        {
-            get => triangleScale;
-            set
-            {
-                float change = value / triangleScale;
-                triangleScale = value;
-
-                for (int i = 0; i < parts.Count; i++)
-                {
-                    TriangleParticle newParticle = parts[i];
-                    newParticle.Scale *= change;
-                    parts[i] = newParticle;
-                }
-            }
+            triangleScale.BindValueChanged(_ => Reset(), true);
         }
 
         protected override void Update()
@@ -147,7 +142,7 @@ protected override void Update()
             // Since position is relative, the velocity needs to scale inversely with DrawHeight.
             // Since we will later multiply by the scale of individual triangles we normalize by
             // dividing by triangleScale.
-            float movedDistance = -elapsedSeconds * Velocity * base_velocity / (DrawHeight * triangleScale);
+            float movedDistance = -elapsedSeconds * Velocity * base_velocity / (DrawHeight * TriangleScale);
 
             for (int i = 0; i < parts.Count; i++)
             {
@@ -159,7 +154,7 @@ protected override void Update()
 
                 parts[i] = newParticle;
 
-                float bottomPos = parts[i].Position.Y + triangle_size * parts[i].Scale * 0.866f / DrawHeight;
+                float bottomPos = parts[i].Position.Y + triangle_size * parts[i].Scale * equilateral_triangle_ratio / DrawHeight;
                 if (bottomPos < 0)
                     parts.RemoveAt(i);
             }
@@ -185,9 +180,11 @@ private void addTriangles(bool randomY)
             // Limited by the maximum size of QuadVertexBuffer for safety.
             const int max_triangles = ushort.MaxValue / (IRenderer.VERTICES_PER_QUAD + 2);
 
-            AimCount = (int)Math.Min(max_triangles, (DrawWidth * DrawHeight * 0.002f / (triangleScale * triangleScale) * SpawnRatio));
+            AimCount = (int)Math.Min(max_triangles, DrawWidth * DrawHeight * 0.002f / (TriangleScale * TriangleScale) * SpawnRatio);
 
-            for (int i = 0; i < AimCount - parts.Count; i++)
+            int currentCount = parts.Count;
+
+            for (int i = 0; i < AimCount - currentCount; i++)
                 parts.Add(createTriangle(randomY));
         }
 
@@ -195,13 +192,27 @@ private TriangleParticle createTriangle(bool randomY)
         {
             TriangleParticle particle = CreateTriangle();
 
-            particle.Position = new Vector2(nextRandom(), randomY ? nextRandom() : 1);
+            particle.Position = getRandomPosition(randomY, particle.Scale);
             particle.ColourShade = nextRandom();
             particle.Colour = CreateTriangleShade(particle.ColourShade);
 
             return particle;
         }
 
+        private Vector2 getRandomPosition(bool randomY, float scale)
+        {
+            float y = 1;
+
+            if (randomY)
+            {
+                // since triangles are drawn from the top - allow them to be positioned a bit above the screen
+                float maxOffset = triangle_size * scale * equilateral_triangle_ratio / DrawHeight;
+                y = Interpolation.ValueAt(nextRandom(), -maxOffset, 1f, 0f, 1f);
+            }
+
+            return new Vector2(nextRandom(), y);
+        }
+
         /// <summary>
         /// Creates a triangle particle with a random scale.
         /// </summary>
@@ -214,7 +225,7 @@ protected virtual TriangleParticle CreateTriangle()
             float u1 = 1 - nextRandom(); //uniform(0,1] random floats
             float u2 = 1 - nextRandom();
             float randStdNormal = (float)(Math.Sqrt(-2.0 * Math.Log(u1)) * Math.Sin(2.0 * Math.PI * u2)); // random normal(0,1)
-            float scale = Math.Max(triangleScale * (mean + std_dev * randStdNormal), 0.1f); // random normal(mean,stdDev^2)
+            float scale = Math.Max(TriangleScale * (mean + std_dev * randStdNormal), 0.1f); // random normal(mean,stdDev^2)
 
             return new TriangleParticle { Scale = scale };
         }
@@ -284,7 +295,7 @@ public override void Draw(IRenderer renderer)
 
                 foreach (TriangleParticle particle in parts)
                 {
-                    var offset = triangle_size * new Vector2(particle.Scale * 0.5f, particle.Scale * 0.866f);
+                    var offset = triangle_size * new Vector2(particle.Scale * 0.5f, particle.Scale * equilateral_triangle_ratio);
 
                     var triangle = new Triangle(
                         Vector2Extensions.Transform(particle.Position * size, DrawInfo.Matrix),