Stable radix sprite sort and render hot-path optimizations
SpriteBatcher now sorts with a stable LSD radix sort: equal-key sprites keep submission order across frames (no flicker) and passes over digits identical in all keys are skipped, making the common single-layer case nearly free. Hot paths avoid per-sprite trig and square roots: SinCos is skipped for unrotated sprites and the culling radius comes from the region's precomputed diagonal. Stress scene (100k entities, ~61k on screen, Release): 103 -> 124 FPS. Sample now runs with VSync off to show real frame rates. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Leonid Pershin
co-authored by
Claude Fable 5
Claude Fable 5
parent
2b7d4c4fef
commit
a3e6d3bb0a
@@ -14,19 +14,40 @@ public static class CullingMath
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{
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var scaledW = regionWidth * transform.Scale.X;
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var scaledH = regionHeight * transform.Scale.Y;
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var center = SpriteCenter(in transform, scaledW, scaledH, origin);
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var radius = 0.5f * MathF.Sqrt(scaledW * scaledW + scaledH * scaledH);
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return (center, radius);
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}
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/// <summary>
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/// Hot-path variant used by the renderer: the radius comes from the region's precomputed
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/// diagonal (no square root per sprite; conservative for non-uniform scale, exact for uniform).
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/// </summary>
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public static (Vector2 Center, float Radius) SpriteBoundingCircle(
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in Transform2D transform, Texture2DRegion region, Vector2 origin)
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{
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var center = SpriteCenter(
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in transform, region.Width * transform.Scale.X, region.Height * transform.Scale.Y, origin);
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var maxScale = MathF.Max(MathF.Abs(transform.Scale.X), MathF.Abs(transform.Scale.Y));
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return (center, 0.5f * region.Diagonal * maxScale);
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}
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private static Vector2 SpriteCenter(in Transform2D transform, float scaledW, float scaledH, Vector2 origin)
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{
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// Offset from the pivot (= transform.Position) to the sprite's geometric center.
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var toCenter = new Vector2(
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scaledW / 2f - origin.X * transform.Scale.X,
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scaledH / 2f - origin.Y * transform.Scale.Y);
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if (transform.Rotation == 0f)
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{
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return transform.Position + toCenter;
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}
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var (sin, cos) = MathF.SinCos(transform.Rotation);
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var center = transform.Position + new Vector2(
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return transform.Position + new Vector2(
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toCenter.X * cos - toCenter.Y * sin,
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toCenter.X * sin + toCenter.Y * cos);
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var radius = 0.5f * MathF.Sqrt(scaledW * scaledW + scaledH * scaledH);
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return (center, radius);
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}
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/// <summary>True when the circle overlaps the rectangle.</summary>
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@@ -97,7 +97,7 @@ public sealed class Renderer2D : IDisposable
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}
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var layer = Layers[sprite.Layer];
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var (center, radius) = CullingMath.SpriteBoundingCircle(transform, region.Width, region.Height, sprite.Origin);
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var (center, radius) = CullingMath.SpriteBoundingCircle(in transform, region, sprite.Origin);
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if (layer.Space == LayerSpace.World &&
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!CullingMath.CircleIntersectsRect(center, radius, Camera.CullRect))
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@@ -203,9 +203,19 @@ public sealed class Renderer2D : IDisposable
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(v0, v1) = (v1, v0);
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}
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var (sin, cos) = MathF.SinCos(instance.Rotation);
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var rx = new Vector2(instance.HalfSize.X * cos, instance.HalfSize.X * sin);
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var ry = new Vector2(-instance.HalfSize.Y * sin, instance.HalfSize.Y * cos);
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Vector2 rx, ry;
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if (instance.Rotation == 0f)
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{
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rx = new Vector2(instance.HalfSize.X, 0f);
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ry = new Vector2(0f, instance.HalfSize.Y);
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}
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else
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{
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var (sin, cos) = MathF.SinCos(instance.Rotation);
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rx = new Vector2(instance.HalfSize.X * cos, instance.HalfSize.X * sin);
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ry = new Vector2(-instance.HalfSize.Y * sin, instance.HalfSize.Y * cos);
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}
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var center = instance.Center;
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var vertex = i * 4;
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@@ -29,14 +29,22 @@ public struct SpriteInstance
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/// <summary>
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/// CPU side of the renderer: collects <see cref="SpriteInstance"/>s with their sort keys
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/// and orders them layer → depth → texture. Allocation-free after warm-up
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/// (arrays grow geometrically and are reused across frames).
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/// and orders them layer → depth → texture using a stable LSD radix sort — sprites with
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/// equal keys keep their submission order across frames (no flicker), and sorting stays
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/// O(n) on large counts. Allocation-free after warm-up (arrays grow geometrically and are
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/// reused across frames).
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/// </summary>
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public sealed class SpriteBatcher
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{
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private const int RadixBits = 16;
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private const int RadixSize = 1 << RadixBits;
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private SpriteInstance[] _instances;
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private ulong[] _keys;
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private ulong[] _keysTemp;
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private int[] _order;
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private int[] _orderTemp;
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private readonly int[] _histogram = new int[RadixSize];
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private int _count;
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/// <summary>Creates a batcher with the given initial capacity.</summary>
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@@ -44,7 +52,9 @@ public sealed class SpriteBatcher
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{
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_instances = new SpriteInstance[initialCapacity];
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_keys = new ulong[initialCapacity];
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_keysTemp = new ulong[initialCapacity];
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_order = new int[initialCapacity];
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_orderTemp = new int[initialCapacity];
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}
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/// <summary>Number of sprites submitted this frame.</summary>
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@@ -64,18 +74,74 @@ public sealed class SpriteBatcher
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}
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/// <summary>
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/// Sorts all submitted sprites and returns their indices in draw order.
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/// Valid until the next <see cref="Clear"/>.
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/// Sorts all submitted sprites (stable: equal keys keep submission order) and returns
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/// their indices in draw order. Valid until the next <see cref="Clear"/>.
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/// </summary>
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public ReadOnlySpan<int> Sort()
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{
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for (var i = 0; i < _count; i++)
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var n = _count;
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for (var i = 0; i < n; i++)
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{
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_order[i] = i;
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}
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Array.Sort(_keys, _order, 0, _count);
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return _order.AsSpan(0, _count);
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if (n < 2)
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{
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return _order.AsSpan(0, n);
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}
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// Биты, различающиеся хотя бы у одной пары ключей: проходы по одинаковым
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// разрядам (один слой, одна глубина) пропускаются целиком.
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ulong orBits = 0, andBits = ~0UL;
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for (var i = 0; i < n; i++)
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{
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orBits |= _keys[i];
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andBits &= _keys[i];
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}
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var differing = orBits ^ andBits;
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var keys = _keys;
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var order = _order;
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var keysOut = _keysTemp;
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var orderOut = _orderTemp;
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for (var shift = 0; shift < 64; shift += RadixBits)
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{
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if ((differing >> shift & (RadixSize - 1)) == 0)
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{
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continue;
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}
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Array.Clear(_histogram, 0, RadixSize);
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for (var i = 0; i < n; i++)
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{
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_histogram[(int)(keys[i] >> shift & (RadixSize - 1))]++;
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}
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var running = 0;
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for (var digit = 0; digit < RadixSize; digit++)
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{
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var bucket = _histogram[digit];
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_histogram[digit] = running;
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running += bucket;
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}
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for (var i = 0; i < n; i++)
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{
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var position = _histogram[(int)(keys[i] >> shift & (RadixSize - 1))]++;
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keysOut[position] = keys[i];
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orderOut[position] = order[i];
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}
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(keys, keysOut) = (keysOut, keys);
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(order, orderOut) = (orderOut, order);
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}
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_keys = keys;
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_keysTemp = keysOut;
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_order = order;
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_orderTemp = orderOut;
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return _order.AsSpan(0, n);
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}
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/// <summary>Returns the instance at <paramref name="index"/> (an index from <see cref="Sort"/>).</summary>
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@@ -89,6 +155,8 @@ public sealed class SpriteBatcher
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var capacity = _instances.Length * 2;
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Array.Resize(ref _instances, capacity);
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Array.Resize(ref _keys, capacity);
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Array.Resize(ref _keysTemp, capacity);
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Array.Resize(ref _order, capacity);
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Array.Resize(ref _orderTemp, capacity);
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}
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}
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@@ -23,6 +23,7 @@ public sealed class Texture2DRegion
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public int Height => Bounds.Height;
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internal readonly int TextureSortKey;
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internal readonly float Diagonal;
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/// <summary>Creates a region covering part of <paramref name="texture"/>.</summary>
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public Texture2DRegion(Texture2D texture, Rectangle bounds)
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@@ -30,6 +31,7 @@ public sealed class Texture2DRegion
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Texture = texture;
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Bounds = bounds;
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TextureSortKey = System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(texture);
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Diagonal = MathF.Sqrt((float)bounds.Width * bounds.Width + (float)bounds.Height * bounds.Height);
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}
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/// <summary>Creates a region covering the whole <paramref name="texture"/>.</summary>
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