phase(N.5b) Task 6: TerrainModernRenderer
The new terrain dispatcher. Single global VBO/EBO with a slot allocator (one slot per landblock, 384 verts × 40 bytes per slot). Per-frame: build DEIC array from visible slots, upload, dispatch via glMultiDrawElementsIndirect. Atlas textures bound via bindless handles set per-frame as sampler uniforms. Total ~6-8 GL calls per frame for terrain regardless of visible landblock count (vs today's per-LB binds at radius=2 → ~25 calls, radius=5 → ~121 calls). API mirrors TerrainChunkRenderer so GameWindow integration in T8 is a drop-in field+ctor swap. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Erik
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344
src/AcDream.App/Rendering/TerrainModernRenderer.cs
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src/AcDream.App/Rendering/TerrainModernRenderer.cs
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using System.Numerics;
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using AcDream.App.Rendering.Wb;
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using AcDream.Core.Terrain;
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using Silk.NET.OpenGL;
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namespace AcDream.App.Rendering;
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/// <summary>
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/// Phase N.5b modern terrain dispatcher. Single global VBO/EBO with a slot
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/// allocator (one slot per landblock, 384 verts × 40 bytes = 15,360 bytes
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/// per slot). Per-frame: build a DrawElementsIndirectCommand array from
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/// visible slots, upload, dispatch via glMultiDrawElementsIndirect. Atlas
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/// textures bound via bindless handles set per-frame as sampler uniforms.
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///
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/// Total ~6-8 GL calls per frame for terrain regardless of visible
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/// landblock count.
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/// </summary>
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public sealed unsafe class TerrainModernRenderer : IDisposable
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{
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private const int VertsPerLandblock = LandblockMesh.VerticesPerLandblock; // 384
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private const int IndicesPerLandblock = VertsPerLandblock;
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private const int VertexSize = 40; // sizeof(TerrainVertex)
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private const int IndexSize = sizeof(uint);
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private const float LandblockSize = LandblockMesh.LandblockSize; // 192
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private readonly GL _gl;
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private readonly BindlessSupport _bindless;
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private readonly Shader _shader;
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private readonly TerrainAtlas _atlas;
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private readonly TerrainSlotAllocator _alloc;
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// Per-slot live data (index by slot integer; null entries are unused slots).
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private SlotData?[] _slots;
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// Reverse map: landblockId -> slot, for RemoveLandblock and replacement.
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private readonly Dictionary<uint, int> _idToSlot = new();
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// GPU buffers.
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private uint _globalVao;
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private uint _globalVbo;
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private uint _globalEbo;
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private uint _indirectBuffer;
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private int _indirectCapacity;
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// Cached sampler-uniform locations (matrix uniforms are set by name via Shader.SetMatrix4).
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private int _uTerrainLoc;
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private int _uAlphaLoc;
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// Reusable per-frame buffers.
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private readonly List<int> _visibleSlots = new();
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private DrawElementsIndirectCommand[] _deicScratch = Array.Empty<DrawElementsIndirectCommand>();
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// Diag.
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public int LoadedSlots => _alloc.LoadedCount;
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public int VisibleSlots => _visibleSlots.Count;
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public int CapacitySlots => _alloc.Capacity;
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public TerrainModernRenderer(
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GL gl,
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BindlessSupport bindless,
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Shader shader,
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TerrainAtlas atlas,
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int initialSlotCapacity = 64)
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{
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_gl = gl;
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_bindless = bindless;
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_shader = shader;
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_atlas = atlas;
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_alloc = new TerrainSlotAllocator(initialSlotCapacity);
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_slots = new SlotData?[initialSlotCapacity];
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_uTerrainLoc = _gl.GetUniformLocation(_shader.Program, "uTerrain");
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_uAlphaLoc = _gl.GetUniformLocation(_shader.Program, "uAlpha");
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_globalVao = _gl.GenVertexArray();
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_globalVbo = _gl.GenBuffer();
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_globalEbo = _gl.GenBuffer();
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AllocateGpuBuffers(initialSlotCapacity);
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ConfigureVao();
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_indirectBuffer = _gl.GenBuffer();
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}
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public void AddLandblock(uint landblockId, LandblockMeshData meshData, Vector3 worldOrigin)
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{
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ArgumentNullException.ThrowIfNull(meshData);
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if (meshData.Vertices.Length != VertsPerLandblock)
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throw new ArgumentException(
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$"Expected {VertsPerLandblock} vertices, got {meshData.Vertices.Length}",
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nameof(meshData));
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if (_idToSlot.ContainsKey(landblockId))
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RemoveLandblock(landblockId);
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int slot = _alloc.Allocate(out var needsGrow);
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if (needsGrow)
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{
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int newCap = Math.Max(_alloc.Capacity * 2, slot + 1);
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EnsureCapacity(newCap);
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}
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// Bake worldOrigin into vertex positions; capture min/max Z for AABB.
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var bakedVerts = new TerrainVertex[VertsPerLandblock];
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float zMin = float.MaxValue, zMax = float.MinValue;
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for (int i = 0; i < VertsPerLandblock; i++)
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{
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var v = meshData.Vertices[i];
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var worldPos = v.Position + worldOrigin;
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bakedVerts[i] = new TerrainVertex(worldPos, v.Normal, v.Data0, v.Data1, v.Data2, v.Data3);
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if (worldPos.Z < zMin) zMin = worldPos.Z;
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if (worldPos.Z > zMax) zMax = worldPos.Z;
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}
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if (zMin == float.MaxValue) { zMin = 0f; zMax = 0f; }
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// Bake baseVertex into indices on the CPU side (driver-portable pattern).
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uint baseVertex = (uint)(slot * VertsPerLandblock);
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var bakedIndices = new uint[IndicesPerLandblock];
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for (int i = 0; i < IndicesPerLandblock; i++)
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bakedIndices[i] = meshData.Indices[i] + baseVertex;
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// glBufferSubData into the slot's VBO + EBO regions.
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nint vboByteOffset = (nint)(slot * VertsPerLandblock * VertexSize);
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nint eboByteOffset = (nint)(slot * IndicesPerLandblock * IndexSize);
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_gl.BindBuffer(BufferTargetARB.ArrayBuffer, _globalVbo);
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fixed (TerrainVertex* p = bakedVerts)
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{
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_gl.BufferSubData(BufferTargetARB.ArrayBuffer, vboByteOffset,
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(nuint)(VertsPerLandblock * VertexSize), p);
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}
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_gl.BindBuffer(BufferTargetARB.ArrayBuffer, 0);
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_gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, _globalEbo);
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fixed (uint* p = bakedIndices)
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{
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_gl.BufferSubData(BufferTargetARB.ElementArrayBuffer, eboByteOffset,
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(nuint)(IndicesPerLandblock * IndexSize), p);
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}
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_gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, 0);
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_slots[slot] = new SlotData
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{
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LandblockId = landblockId,
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WorldOrigin = worldOrigin,
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FirstIndex = (uint)(slot * IndicesPerLandblock),
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IndexCount = IndicesPerLandblock,
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AabbMin = new Vector3(worldOrigin.X, worldOrigin.Y, zMin),
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AabbMax = new Vector3(worldOrigin.X + LandblockSize, worldOrigin.Y + LandblockSize, zMax),
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};
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_idToSlot[landblockId] = slot;
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}
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public void RemoveLandblock(uint landblockId)
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{
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if (!_idToSlot.TryGetValue(landblockId, out var slot))
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return;
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_idToSlot.Remove(landblockId);
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_slots[slot] = null;
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_alloc.Free(slot);
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// No GPU clear: the per-frame DEIC array won't reference this slot.
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}
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public void Draw(ICamera camera, FrustumPlanes? frustum = null, uint? neverCullLandblockId = null)
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{
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if (_alloc.LoadedCount == 0) return;
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// Build visible slot list with per-slot frustum cull.
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_visibleSlots.Clear();
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for (int slot = 0; slot < _slots.Length; slot++)
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{
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var data = _slots[slot];
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if (data is null) continue;
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if (frustum is not null && data.LandblockId != neverCullLandblockId)
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{
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if (!FrustumCuller.IsAabbVisible(frustum.Value, data.AabbMin, data.AabbMax))
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continue;
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}
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_visibleSlots.Add(slot);
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}
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if (_visibleSlots.Count == 0) return;
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// Build DEIC array.
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if (_deicScratch.Length < _visibleSlots.Count)
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_deicScratch = new DrawElementsIndirectCommand[Math.Max(_visibleSlots.Count, 64)];
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for (int i = 0; i < _visibleSlots.Count; i++)
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{
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var data = _slots[_visibleSlots[i]]!;
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_deicScratch[i] = new DrawElementsIndirectCommand
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{
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Count = (uint)data.IndexCount,
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InstanceCount = 1u,
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FirstIndex = data.FirstIndex,
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BaseVertex = 0, // baked into indices on upload
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BaseInstance = 0,
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};
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}
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// Grow indirect buffer if needed.
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if (_visibleSlots.Count > _indirectCapacity)
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{
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_indirectCapacity = Math.Max(64, _visibleSlots.Count * 2);
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_gl.BindBuffer(GLEnum.DrawIndirectBuffer, _indirectBuffer);
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_gl.BufferData(GLEnum.DrawIndirectBuffer,
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(nuint)(_indirectCapacity * sizeof(DrawElementsIndirectCommand)),
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null, GLEnum.DynamicDraw);
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}
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else
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{
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_gl.BindBuffer(GLEnum.DrawIndirectBuffer, _indirectBuffer);
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}
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// Upload DEIC array.
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fixed (DrawElementsIndirectCommand* p = _deicScratch)
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{
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_gl.BufferSubData(GLEnum.DrawIndirectBuffer, 0,
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(nuint)(_visibleSlots.Count * sizeof(DrawElementsIndirectCommand)), p);
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}
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// Bind shader + uniforms + atlas handles.
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_shader.Use();
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_shader.SetMatrix4("uView", camera.View);
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_shader.SetMatrix4("uProjection", camera.Projection);
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var (terrainHandle, alphaHandle) = _atlas.GetBindlessHandles();
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_bindless.SetSamplerHandleUniform(_shader.Program, _uTerrainLoc, terrainHandle);
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_bindless.SetSamplerHandleUniform(_shader.Program, _uAlphaLoc, alphaHandle);
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_gl.BindVertexArray(_globalVao);
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_gl.MemoryBarrier(MemoryBarrierMask.CommandBarrierBit);
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_gl.MultiDrawElementsIndirect(
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PrimitiveType.Triangles, DrawElementsType.UnsignedInt,
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(void*)0,
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(uint)_visibleSlots.Count,
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(uint)sizeof(DrawElementsIndirectCommand));
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_gl.BindVertexArray(0);
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_gl.BindBuffer(GLEnum.DrawIndirectBuffer, 0);
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}
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public void Dispose()
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{
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_gl.DeleteVertexArray(_globalVao);
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_gl.DeleteBuffer(_globalVbo);
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_gl.DeleteBuffer(_globalEbo);
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_gl.DeleteBuffer(_indirectBuffer);
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}
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// ----------------------------------------------------------------
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// Private helpers
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// ----------------------------------------------------------------
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private void AllocateGpuBuffers(int capacitySlots)
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{
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nuint vboBytes = (nuint)(capacitySlots * VertsPerLandblock * VertexSize);
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nuint eboBytes = (nuint)(capacitySlots * IndicesPerLandblock * IndexSize);
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_gl.BindBuffer(BufferTargetARB.ArrayBuffer, _globalVbo);
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_gl.BufferData(BufferTargetARB.ArrayBuffer, vboBytes, null, BufferUsageARB.DynamicDraw);
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_gl.BindBuffer(BufferTargetARB.ArrayBuffer, 0);
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_gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, _globalEbo);
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_gl.BufferData(BufferTargetARB.ElementArrayBuffer, eboBytes, null, BufferUsageARB.DynamicDraw);
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_gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, 0);
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}
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private void ConfigureVao()
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{
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_gl.BindVertexArray(_globalVao);
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_gl.BindBuffer(BufferTargetARB.ArrayBuffer, _globalVbo);
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_gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, _globalEbo);
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uint stride = (uint)VertexSize;
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// location 0: Position
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_gl.EnableVertexAttribArray(0);
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_gl.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, stride, (void*)0);
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// location 1: Normal
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_gl.EnableVertexAttribArray(1);
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_gl.VertexAttribPointer(1, 3, VertexAttribPointerType.Float, false, stride, (void*)(3 * sizeof(float)));
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// locations 2-5: Data0..Data3 (uvec4 byte attributes)
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nint dataOffset = 6 * sizeof(float);
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_gl.EnableVertexAttribArray(2);
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_gl.VertexAttribIPointer(2, 4, VertexAttribIType.UnsignedByte, stride, (void*)dataOffset);
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_gl.EnableVertexAttribArray(3);
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_gl.VertexAttribIPointer(3, 4, VertexAttribIType.UnsignedByte, stride, (void*)(dataOffset + 4));
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_gl.EnableVertexAttribArray(4);
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_gl.VertexAttribIPointer(4, 4, VertexAttribIType.UnsignedByte, stride, (void*)(dataOffset + 8));
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_gl.EnableVertexAttribArray(5);
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_gl.VertexAttribIPointer(5, 4, VertexAttribIType.UnsignedByte, stride, (void*)(dataOffset + 12));
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_gl.BindVertexArray(0);
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}
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private void EnsureCapacity(int newCapacity)
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{
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if (newCapacity <= _alloc.Capacity) return;
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// Allocate new VBO + EBO at new size; copy old contents; swap; recreate VAO.
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uint newVbo = _gl.GenBuffer();
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uint newEbo = _gl.GenBuffer();
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nuint newVboBytes = (nuint)(newCapacity * VertsPerLandblock * VertexSize);
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nuint newEboBytes = (nuint)(newCapacity * IndicesPerLandblock * IndexSize);
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nuint oldVboBytes = (nuint)(_alloc.Capacity * VertsPerLandblock * VertexSize);
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nuint oldEboBytes = (nuint)(_alloc.Capacity * IndicesPerLandblock * IndexSize);
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_gl.BindBuffer(BufferTargetARB.ArrayBuffer, newVbo);
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_gl.BufferData(BufferTargetARB.ArrayBuffer, newVboBytes, null, BufferUsageARB.DynamicDraw);
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_gl.BindBuffer(BufferTargetARB.CopyReadBuffer, _globalVbo);
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_gl.BindBuffer(BufferTargetARB.CopyWriteBuffer, newVbo);
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_gl.CopyBufferSubData(CopyBufferSubDataTarget.CopyReadBuffer, CopyBufferSubDataTarget.CopyWriteBuffer,
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0, 0, oldVboBytes);
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_gl.DeleteBuffer(_globalVbo);
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_globalVbo = newVbo;
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_gl.BindBuffer(BufferTargetARB.ElementArrayBuffer, newEbo);
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_gl.BufferData(BufferTargetARB.ElementArrayBuffer, newEboBytes, null, BufferUsageARB.DynamicDraw);
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_gl.BindBuffer(BufferTargetARB.CopyReadBuffer, _globalEbo);
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_gl.BindBuffer(BufferTargetARB.CopyWriteBuffer, newEbo);
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_gl.CopyBufferSubData(CopyBufferSubDataTarget.CopyReadBuffer, CopyBufferSubDataTarget.CopyWriteBuffer,
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0, 0, oldEboBytes);
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_gl.DeleteBuffer(_globalEbo);
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_globalEbo = newEbo;
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// Recreate VAO with new buffer bindings.
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_gl.DeleteVertexArray(_globalVao);
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_globalVao = _gl.GenVertexArray();
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ConfigureVao();
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// Grow slot tracking array.
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Array.Resize(ref _slots, newCapacity);
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_alloc.GrowTo(newCapacity);
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}
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private sealed class SlotData
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{
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public uint LandblockId;
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public Vector3 WorldOrigin;
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public uint FirstIndex;
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public int IndexCount;
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public Vector3 AabbMin;
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public Vector3 AabbMax;
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}
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}
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@ -45,6 +45,15 @@ public sealed class BindlessSupport
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_ext.MakeTextureHandleNonResident(handle);
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}
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/// <summary>
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/// Set a sampler-typed uniform from a 64-bit bindless handle. Uses
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/// glProgramUniformHandleARB so it doesn't require the program to be bound.
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/// </summary>
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public void SetSamplerHandleUniform(uint program, int location, ulong handle)
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{
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_ext.ProgramUniformHandle(program, location, handle);
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}
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/// <summary>Detect <c>GL_ARB_shader_draw_parameters</c> in addition to bindless.
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/// N.5's vertex shader uses <c>gl_BaseInstanceARB</c> and <c>gl_DrawIDARB</c>
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/// from this extension.</summary>
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