Finding some common ground

- Make MeshPool common between instancing and indirect
- Remove empty instancers and delete meshes on indirect
- Inline IndirectModel into IndirectInstancer since it was basically
  just a thin wrapper
- Share one meshpool between all culling groups
- Always upload draw commands because the mesh may have moved
- No longer need to set the base instance in the apply shader

src/main/java/com/jozufozu/flywheel/backend/engine/AbstractInstancer.java

@@ -81,19 +81,19 @@ public abstract class AbstractInstancer<I extends Instance> implements Instancer
 		changed.set(handle.index);
 	}
 
-	public int getInstanceCount() {
+	public int instanceCount() {
 		return instances.size();
 	}
 
 	public void notifyDirty(int index) {
-		if (index < 0 || index >= getInstanceCount()) {
+		if (index < 0 || index >= instanceCount()) {
 			return;
 		}
 		changed.set(index);
 	}
 
 	public void notifyRemoval(int index) {
-		if (index < 0 || index >= getInstanceCount()) {
+		if (index < 0 || index >= instanceCount()) {
 			return;
 		}
 		deleted.set(index);
@@ -159,6 +159,6 @@ public abstract class AbstractInstancer<I extends Instance> implements Instancer
 
 	@Override
 	public String toString() {
-		return "AbstractInstancer[" + getInstanceCount() + ']';
+		return "AbstractInstancer[" + instanceCount() + ']';
 	}
 }

src/main/java/com/jozufozu/flywheel/backend/engine/MeshPool.java

@@ -0,0 +1,249 @@
+package com.jozufozu.flywheel.backend.engine;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import org.jetbrains.annotations.Nullable;
+import org.lwjgl.opengl.GL32;
+
+import com.jozufozu.flywheel.api.model.IndexSequence;
+import com.jozufozu.flywheel.api.model.Mesh;
+import com.jozufozu.flywheel.api.vertex.VertexView;
+import com.jozufozu.flywheel.backend.InternalVertex;
+import com.jozufozu.flywheel.backend.gl.GlNumericType;
+import com.jozufozu.flywheel.backend.gl.GlPrimitive;
+import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
+import com.jozufozu.flywheel.backend.gl.buffer.GlBuffer;
+import com.jozufozu.flywheel.lib.memory.MemoryBlock;
+
+import it.unimi.dsi.fastutil.objects.Reference2IntMap;
+import it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceArraySet;
+
+public class MeshPool {
+	private final VertexView vertexView;
+	private final Map<Mesh, BufferedMesh> meshes = new HashMap<>();
+	private final List<BufferedMesh> meshList = new ArrayList<>();
+
+	private final GlBuffer vbo;
+	private final GlBuffer ebo;
+
+	private boolean dirty;
+	private boolean anyToRemove;
+
+	/**
+	 * Create a new mesh pool.
+	 */
+	public MeshPool() {
+		vertexView = InternalVertex.createVertexView();
+		vbo = new GlBuffer();
+		ebo = new GlBuffer();
+	}
+
+	/**
+	 * Allocate a model in the arena.
+	 *
+	 * @param mesh The model to allocate.
+	 * @return A handle to the allocated model.
+	 */
+	public BufferedMesh alloc(Mesh mesh) {
+		return meshes.computeIfAbsent(mesh, this::_alloc);
+	}
+
+	private BufferedMesh _alloc(Mesh m) {
+		BufferedMesh bufferedModel = new BufferedMesh(m);
+		meshList.add(bufferedModel);
+
+		dirty = true;
+		return bufferedModel;
+	}
+
+	@Nullable
+	public BufferedMesh get(Mesh mesh) {
+		return meshes.get(mesh);
+	}
+
+	public void flush() {
+        if (!dirty) {
+            return;
+        }
+
+		if (anyToRemove) {
+			anyToRemove = false;
+			processDeletions();
+		}
+
+        uploadAll();
+        dirty = false;
+    }
+
+	private void processDeletions() {
+		// remove deleted meshes
+		meshList.removeIf(bufferedMesh -> {
+			boolean deleted = bufferedMesh.deleted();
+			if (deleted) {
+				meshes.remove(bufferedMesh.mesh);
+			}
+			return deleted;
+		});
+	}
+
+	private void uploadAll() {
+		long neededSize = 0;
+		Reference2IntMap<IndexSequence> indexCounts = new Reference2IntOpenHashMap<>();
+		indexCounts.defaultReturnValue(0);
+
+		for (BufferedMesh mesh : meshList) {
+			neededSize += mesh.byteSize();
+
+			int count = indexCounts.getInt(mesh.mesh.indexSequence());
+			int newCount = Math.max(count, mesh.indexCount());
+
+			if (newCount > count) {
+				indexCounts.put(mesh.mesh.indexSequence(), newCount);
+			}
+		}
+
+		long totalIndexCount = 0;
+
+		for (int count : indexCounts.values()) {
+			totalIndexCount += count;
+		}
+
+		final var indexBlock = MemoryBlock.malloc(totalIndexCount * GlNumericType.UINT.byteWidth());
+		final long indexPtr = indexBlock.ptr();
+
+		Reference2IntMap<IndexSequence> firstIndices = new Reference2IntOpenHashMap<>();
+
+		int firstIndex = 0;
+		for (Reference2IntMap.Entry<IndexSequence> entries : indexCounts.reference2IntEntrySet()) {
+			var indexSequence = entries.getKey();
+			var indexCount = entries.getIntValue();
+
+			firstIndices.put(indexSequence, firstIndex);
+
+			indexSequence.fill(indexPtr + (long) firstIndex * GlNumericType.UINT.byteWidth(), indexCount);
+
+			firstIndex += indexCount;
+		}
+
+		final var vertexBlock = MemoryBlock.malloc(neededSize);
+		final long vertexPtr = vertexBlock.ptr();
+
+		int byteIndex = 0;
+		int baseVertex = 0;
+		for (BufferedMesh mesh : meshList) {
+			mesh.byteIndex = byteIndex;
+			mesh.baseVertex = baseVertex;
+
+			mesh.write(vertexPtr, vertexView);
+
+			byteIndex += mesh.byteSize();
+			baseVertex += mesh.vertexCount();
+
+			mesh.firstIndex = firstIndices.getInt(mesh.mesh.indexSequence());
+		}
+
+		vbo.upload(vertexBlock);
+		ebo.upload(indexBlock);
+
+		vertexBlock.free();
+		indexBlock.free();
+	}
+
+	public void bind(GlVertexArray vertexArray) {
+		vertexArray.setElementBuffer(ebo.handle());
+		vertexArray.bindVertexBuffer(0, vbo.handle(), 0, InternalVertex.STRIDE);
+		vertexArray.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
+	}
+
+	public void delete() {
+		vbo.delete();
+		ebo.delete();
+		meshes.clear();
+		meshList.clear();
+	}
+
+	public class BufferedMesh {
+		private final Mesh mesh;
+		private final int vertexCount;
+		private final int byteSize;
+
+		private long byteIndex;
+		private int baseVertex;
+		private int firstIndex;
+
+		private int referenceCount = 0;
+		private final Set<GlVertexArray> boundTo = new ReferenceArraySet<>();
+
+		private BufferedMesh(Mesh mesh) {
+			this.mesh = mesh;
+			vertexCount = mesh.vertexCount();
+			byteSize = vertexCount * InternalVertex.STRIDE;
+		}
+
+		public int vertexCount() {
+			return vertexCount;
+		}
+
+		public int byteSize() {
+			return byteSize;
+		}
+
+		public int indexCount() {
+			return mesh.indexCount();
+		}
+
+		public int baseVertex() {
+			return baseVertex;
+		}
+
+		public int firstIndex() {
+			return firstIndex;
+		}
+
+		public boolean deleted() {
+			return referenceCount <= 0;
+		}
+
+		public boolean invalid() {
+			return mesh.vertexCount() == 0 || deleted() || byteIndex == -1;
+		}
+
+		private void write(long ptr, VertexView vertexView) {
+			vertexView.ptr(ptr + byteIndex);
+			vertexView.vertexCount(vertexCount);
+			mesh.write(vertexView);
+		}
+
+		public void draw(int instanceCount) {
+			if (instanceCount > 1) {
+				GL32.glDrawElementsInstanced(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, firstIndex, instanceCount);
+			} else {
+				GL32.glDrawElements(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, firstIndex);
+			}
+		}
+
+		public void setup(GlVertexArray vao) {
+			if (boundTo.add(vao)) {
+				vao.setElementBuffer(MeshPool.this.ebo.handle());
+				vao.bindVertexBuffer(0, MeshPool.this.vbo.handle(), byteIndex, InternalVertex.STRIDE);
+				vao.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
+			}
+		}
+
+		public void acquire() {
+			referenceCount++;
+		}
+
+		public void drop() {
+			if (--referenceCount == 0) {
+				MeshPool.this.dirty = true;
+				MeshPool.this.anyToRemove = true;
+			}
+		}
+	}
+}

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectCullingGroup.java

@@ -25,6 +25,7 @@ import com.jozufozu.flywheel.api.model.Mesh;
 import com.jozufozu.flywheel.api.model.Model;
 import com.jozufozu.flywheel.backend.compile.IndirectPrograms;
 import com.jozufozu.flywheel.backend.engine.MaterialRenderState;
+import com.jozufozu.flywheel.backend.engine.MeshPool;
 import com.jozufozu.flywheel.backend.engine.textures.TextureBinder;
 import com.jozufozu.flywheel.backend.engine.textures.TextureSourceImpl;
 import com.jozufozu.flywheel.backend.engine.uniform.Uniforms;
@@ -43,8 +44,7 @@ public class IndirectCullingGroup<I extends Instance> {
 	private final Context context;
 	private final long objectStride;
 	private final IndirectBuffers buffers;
-	private final IndirectMeshPool meshPool;
-	private final List<IndirectModel> indirectModels = new ArrayList<>();
+	private final List<IndirectInstancer<?>> instancers = new ArrayList<>();
 	private final List<IndirectDraw> indirectDraws = new ArrayList<>();
 	private final Map<RenderStage, List<MultiDraw>> multiDraws = new EnumMap<>(RenderStage.class);
 
@@ -54,7 +54,7 @@ public class IndirectCullingGroup<I extends Instance> {
 	private final GlProgram drawProgram;
 
 	private boolean needsDrawBarrier;
-	private boolean hasNewDraws;
+	private boolean needsDrawSort;
 	private int instanceCountThisFrame;
 
 	IndirectCullingGroup(InstanceType<I> instanceType, Context context, IndirectPrograms programs) {
@@ -63,7 +63,6 @@ public class IndirectCullingGroup<I extends Instance> {
 		objectStride = instanceType.layout()
 				.byteSize() + IndirectBuffers.INT_SIZE;
 		buffers = new IndirectBuffers(objectStride);
-		meshPool = new IndirectMeshPool();
 
 		this.programs = programs;
 		// TODO: Culling programs need to be context aware.
@@ -72,18 +71,40 @@ public class IndirectCullingGroup<I extends Instance> {
 		drawProgram = programs.getIndirectProgram(instanceType, context.contextShader());
 	}
 
-	public void flush(StagingBuffer stagingBuffer) {
-		needsDrawBarrier = true;
-		instanceCountThisFrame = prepareModels();
+	public void flushInstancers() {
+		instanceCountThisFrame = 0;
+		int modelIndex = 0;
+        for (var iterator = instancers.iterator(); iterator.hasNext(); ) {
+            var instancer = iterator.next();
+            instancer.update();
+			var instanceCount = instancer.instanceCount();
 
+			if (instanceCount == 0) {
+				iterator.remove();
+				for (IndirectDraw draw : instancer.draws()) {
+					draw.delete();
+				}
+				continue;
+			}
+
+			instancer.index = modelIndex;
+			instancer.baseInstance = instanceCountThisFrame;
+			instanceCountThisFrame += instanceCount;
+
+			modelIndex++;
+        }
+
+        if (indirectDraws.removeIf(IndirectDraw::deleted)) {
+			needsDrawSort = true;
+		}
+	}
+
+	public void upload(StagingBuffer stagingBuffer) {
 		if (nothingToDo()) {
 			return;
 		}
 
-		buffers.updateCounts(instanceCountThisFrame, indirectModels.size(), indirectDraws.size());
-
-		// Must flush the mesh pool first so everything else has the right baseVertex and baseIndex.
-		meshPool.flush();
+		buffers.updateCounts(instanceCountThisFrame, instancers.size(), indirectDraws.size());
 
 		// Upload only objects that have changed.
 		uploadObjects(stagingBuffer);
@@ -91,14 +112,14 @@ public class IndirectCullingGroup<I extends Instance> {
 		// We need to upload the models every frame to reset the instance count.
 		uploadModels(stagingBuffer);
 
-		if (hasNewDraws) {
+		if (needsDrawSort) {
 			sortDraws();
-			// Draws, however, only need to be updated when we get new ones.
-			// The instanceCount and baseInstance will be updated by the applyProgram,
-			// and all other fields are constant to the lifetime of the draw.
-			uploadDraws(stagingBuffer);
-			hasNewDraws = false;
+			needsDrawSort = false;
 		}
+
+		uploadDraws(stagingBuffer);
+
+		needsDrawBarrier = true;
 	}
 
 	public void dispatchCull() {
@@ -132,18 +153,6 @@ public class IndirectCullingGroup<I extends Instance> {
 		return nothingToDo() || !multiDraws.containsKey(stage);
 	}
 
-	/**
-	 * @return the total instance count
-	 */
-	private int prepareModels() {
-		int baseInstance = 0;
-		for (var model : indirectModels) {
-			model.prepare(baseInstance);
-			baseInstance += model.instancer.getInstanceCount();
-		}
-		return baseInstance;
-	}
-
 	private void sortDraws() {
 		multiDraws.clear();
 		// sort by stage, then material
@@ -169,20 +178,18 @@ public class IndirectCullingGroup<I extends Instance> {
 		return multiDraws.containsKey(stage);
 	}
 
-	public void add(IndirectInstancer<I> instancer, Model model, RenderStage stage) {
-		int modelIndex = indirectModels.size();
-		instancer.setModelIndex(modelIndex);
-		var indirectModel = new IndirectModel(instancer, modelIndex, model.boundingSphere());
-		indirectModels.add(indirectModel);
+	public void add(IndirectInstancer<I> instancer, Model model, RenderStage stage, MeshPool meshPool) {
+        instancer.index = instancers.size();
+		instancers.add(instancer);
 
 		for (Map.Entry<Material, Mesh> entry : model.meshes().entrySet()) {
-			IndirectMeshPool.BufferedMesh bufferedMesh = meshPool.alloc(entry.getValue());
-			var draw = new IndirectDraw(indirectModel, entry.getKey(), bufferedMesh, stage);
+			MeshPool.BufferedMesh bufferedMesh = meshPool.alloc(entry.getValue());
+			var draw = new IndirectDraw(instancer, entry.getKey(), bufferedMesh, stage);
 			indirectDraws.add(draw);
 			instancer.addDraw(draw);
 		}
 
-		hasNewDraws = true;
+		needsDrawSort = true;
 	}
 
 	public void submit(RenderStage stage, TextureSourceImpl textures) {
@@ -190,9 +197,7 @@ public class IndirectCullingGroup<I extends Instance> {
 			return;
 		}
 
-		Uniforms.bindForDraw();
 		drawProgram.bind();
-		meshPool.bindForDraw();
 		buffers.bindForDraw();
 
 		drawBarrier();
@@ -215,8 +220,6 @@ public class IndirectCullingGroup<I extends Instance> {
 
 		program.bind();
 
-		Uniforms.bindForDraw();
-		meshPool.bindForDraw();
 		buffers.bindForCrumbling();
 
 		drawBarrier();
@@ -236,8 +239,8 @@ public class IndirectCullingGroup<I extends Instance> {
 
 	private void uploadObjects(StagingBuffer stagingBuffer) {
 		long pos = 0;
-		for (IndirectModel model : indirectModels) {
-			var instanceCount = model.instancer.getInstanceCount();
+		for (var model : instancers) {
+			var instanceCount = model.instanceCount();
 			model.uploadObjects(stagingBuffer, pos, buffers.object.handle());
 
 			pos += instanceCount * objectStride;
@@ -245,7 +248,7 @@ public class IndirectCullingGroup<I extends Instance> {
 	}
 
 	private void uploadModels(StagingBuffer stagingBuffer) {
-		var totalSize = indirectModels.size() * IndirectBuffers.MODEL_STRIDE;
+		var totalSize = instancers.size() * IndirectBuffers.MODEL_STRIDE;
 		var handle = buffers.model.handle();
 
 		stagingBuffer.enqueueCopy(totalSize, handle, 0, this::writeModels);
@@ -259,8 +262,8 @@ public class IndirectCullingGroup<I extends Instance> {
 	}
 
 	private void writeModels(long writePtr) {
-		for (var model : indirectModels) {
-			model.write(writePtr);
+		for (var model : instancers) {
+			model.writeModel(writePtr);
 			writePtr += IndirectBuffers.MODEL_STRIDE;
 		}
 	}
@@ -274,7 +277,6 @@ public class IndirectCullingGroup<I extends Instance> {
 
 	public void delete() {
 		buffers.delete();
-		meshPool.delete();
 	}
 
 	private record MultiDraw(Material material, int start, int end) {

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectDraw.java

@@ -6,35 +6,43 @@ import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.material.Material;
 import com.jozufozu.flywheel.backend.ShaderIndices;
 import com.jozufozu.flywheel.backend.engine.MaterialEncoder;
+import com.jozufozu.flywheel.backend.engine.MeshPool;
 
 public class IndirectDraw {
-	private final IndirectModel model;
+	private final IndirectInstancer<?> model;
 	private final Material material;
-	private final IndirectMeshPool.BufferedMesh mesh;
+	private final MeshPool.BufferedMesh mesh;
 	private final RenderStage stage;
 
 	private final int materialVertexIndex;
 	private final int materialFragmentIndex;
 	private final int packedFogAndCutout;
 	private final int packedMaterialProperties;
+	private boolean deleted;
 
-	public IndirectDraw(IndirectModel model, Material material, IndirectMeshPool.BufferedMesh mesh, RenderStage stage) {
+	public IndirectDraw(IndirectInstancer<?> model, Material material, MeshPool.BufferedMesh mesh, RenderStage stage) {
 		this.model = model;
 		this.material = material;
 		this.mesh = mesh;
 		this.stage = stage;
 
+		mesh.acquire();
+
 		this.materialVertexIndex = ShaderIndices.getVertexShaderIndex(material.shaders());
 		this.materialFragmentIndex = ShaderIndices.getFragmentShaderIndex(material.shaders());
 		this.packedFogAndCutout = MaterialEncoder.packFogAndCutout(material);
 		this.packedMaterialProperties = MaterialEncoder.packProperties(material);
 	}
 
+	public boolean deleted() {
+		return deleted;
+	}
+
 	public Material material() {
 		return material;
 	}
 
-	public IndirectMeshPool.BufferedMesh mesh() {
+	public MeshPool.BufferedMesh mesh() {
 		return mesh;
 	}
 
@@ -47,9 +55,9 @@ public class IndirectDraw {
 		MemoryUtil.memPutInt(ptr + 4, 0); // instanceCount - to be set by the apply shader
 		MemoryUtil.memPutInt(ptr + 8, mesh.firstIndex()); // firstIndex
 		MemoryUtil.memPutInt(ptr + 12, mesh.baseVertex()); // baseVertex
-		MemoryUtil.memPutInt(ptr + 16, 0); // baseInstance - to be set by the apply shader
+		MemoryUtil.memPutInt(ptr + 16, model.baseInstance); // baseInstance
 
-		MemoryUtil.memPutInt(ptr + 20, model.index); // modelIndex - never changes
+		MemoryUtil.memPutInt(ptr + 20, model.index); // modelIndex
 
 		MemoryUtil.memPutInt(ptr + 24, materialVertexIndex); // materialVertexIndex
 		MemoryUtil.memPutInt(ptr + 28, materialFragmentIndex); // materialFragmentIndex
@@ -62,7 +70,7 @@ public class IndirectDraw {
 		MemoryUtil.memPutInt(ptr + 4, 1); // instanceCount - only drawing one instance
 		MemoryUtil.memPutInt(ptr + 8, mesh.firstIndex()); // firstIndex
 		MemoryUtil.memPutInt(ptr + 12, mesh.baseVertex()); // baseVertex
-		MemoryUtil.memPutInt(ptr + 16, model.baseInstance() + instanceIndex); // baseInstance
+		MemoryUtil.memPutInt(ptr + 16, model.baseInstance + instanceIndex); // baseInstance
 
 		MemoryUtil.memPutInt(ptr + 20, model.index); // modelIndex
 
@@ -71,4 +79,14 @@ public class IndirectDraw {
 		MemoryUtil.memPutInt(ptr + 32, MaterialEncoder.packFogAndCutout(materialOverride)); // packedFogAndCutout
 		MemoryUtil.memPutInt(ptr + 36, MaterialEncoder.packProperties(materialOverride)); // packedMaterialProperties
 	}
+
+	public void delete() {
+		if (deleted) {
+			return;
+		}
+
+		mesh.drop();
+
+		deleted = true;
+	}
 }

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectDrawManager.java

@@ -22,9 +22,12 @@ import com.jozufozu.flywheel.backend.engine.InstanceHandleImpl;
 import com.jozufozu.flywheel.backend.engine.InstancerKey;
 import com.jozufozu.flywheel.backend.engine.InstancerStorage;
 import com.jozufozu.flywheel.backend.engine.MaterialRenderState;
+import com.jozufozu.flywheel.backend.engine.MeshPool;
 import com.jozufozu.flywheel.backend.engine.textures.TextureBinder;
 import com.jozufozu.flywheel.backend.engine.textures.TextureSourceImpl;
+import com.jozufozu.flywheel.backend.engine.uniform.Uniforms;
 import com.jozufozu.flywheel.backend.gl.GlStateTracker;
+import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
 import com.jozufozu.flywheel.backend.gl.buffer.GlBuffer;
 import com.jozufozu.flywheel.backend.gl.buffer.GlBufferType;
 import com.jozufozu.flywheel.lib.context.ContextShaders;
@@ -40,6 +43,8 @@ import net.minecraft.client.resources.model.ModelBakery;
 public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>> {
 	private final IndirectPrograms programs;
 	private final StagingBuffer stagingBuffer;
+	private final MeshPool meshPool;
+	private final GlVertexArray vertexArray;
 	private final TextureSourceImpl textures = new TextureSourceImpl();
 	private final Map<GroupKey<?>, IndirectCullingGroup<?>> cullingGroups = new HashMap<>();
 	private final GlBuffer crumblingDrawBuffer = new GlBuffer();
@@ -47,11 +52,17 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 	public IndirectDrawManager(IndirectPrograms programs) {
 		this.programs = programs;
 		stagingBuffer = new StagingBuffer(this.programs);
+
+		meshPool = new MeshPool();
+
+		vertexArray = GlVertexArray.create();
+
+		meshPool.bind(vertexArray);
 	}
 
 	@Override
 	protected <I extends Instance> IndirectInstancer<?> create(InstancerKey<I> key) {
-		return new IndirectInstancer<>(key.type(), key.context());
+		return new IndirectInstancer<>(key.type(), key.context(), key.model());
 	}
 
 	@SuppressWarnings("unchecked")
@@ -59,7 +70,7 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 	protected <I extends Instance> void initialize(InstancerKey<I> key, IndirectInstancer<?> instancer) {
 		var groupKey = new GroupKey<>(key.type(), key.context());
 		var group = (IndirectCullingGroup<I>) cullingGroups.computeIfAbsent(groupKey, t -> new IndirectCullingGroup<>(t.type, t.context, programs));
-		group.add((IndirectInstancer<I>) instancer, key.model(), key.stage());
+		group.add((IndirectInstancer<I>) instancer, key.model(), key.stage(), meshPool);
 	}
 
 	public boolean hasStage(RenderStage stage) {
@@ -74,6 +85,9 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 	public void renderStage(RenderStage stage) {
 		TextureBinder.bindLightAndOverlay();
 
+		vertexArray.bindForDraw();
+		Uniforms.bindForDraw();
+
 		for (var group : cullingGroups.values()) {
 			group.submit(stage, textures);
 		}
@@ -86,10 +100,18 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 	public void flush() {
 		super.flush();
 
+		for (var group : cullingGroups.values()) {
+			group.flushInstancers();
+		}
+
+		instancers.values().removeIf(instancer -> instancer.instanceCount() == 0);
+
+		meshPool.flush();
+
 		stagingBuffer.reclaim();
 
 		for (var group : cullingGroups.values()) {
-			group.flush(stagingBuffer);
+			group.upload(stagingBuffer);
 		}
 
 		stagingBuffer.flush();
@@ -113,6 +135,8 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 
 		stagingBuffer.delete();
 
+		meshPool.delete();
+
 		crumblingDrawBuffer.delete();
 	}
 
@@ -126,6 +150,9 @@ public class IndirectDrawManager extends InstancerStorage<IndirectInstancer<?>>
 		try (var state = GlStateTracker.getRestoreState()) {
 			TextureBinder.bindLightAndOverlay();
 
+			vertexArray.bindForDraw();
+			Uniforms.bindForDraw();
+
 			var crumblingMaterial = SimpleMaterial.builder();
 
 			// Scratch memory for writing draw commands.

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectInstancer.java

@@ -3,27 +3,34 @@ package com.jozufozu.flywheel.backend.engine.indirect;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.joml.Vector4fc;
 import org.lwjgl.system.MemoryUtil;
 
 import com.jozufozu.flywheel.api.context.Context;
 import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.api.instance.InstanceType;
 import com.jozufozu.flywheel.api.instance.InstanceWriter;
+import com.jozufozu.flywheel.api.model.Model;
 import com.jozufozu.flywheel.backend.engine.AbstractInstancer;
 
 public class IndirectInstancer<I extends Instance> extends AbstractInstancer<I> {
 	private final long objectStride;
 	private final InstanceWriter<I> writer;
 	private final List<IndirectDraw> associatedDraws = new ArrayList<>();
-	private int modelIndex;
+	private final Vector4fc boundingSphere;
 
+
+	public int index;
+	public int baseInstance = -1;
+	private int lastModelIndex = -1;
 	private long lastStartPos = -1;
 
-	public IndirectInstancer(InstanceType<I> type, Context context) {
+	public IndirectInstancer(InstanceType<I> type, Context context, Model model) {
 		super(type, context);
 		this.objectStride = type.layout()
 				.byteSize() + IndirectBuffers.INT_SIZE;
 		writer = this.type.writer();
+		boundingSphere = model.boundingSphere();
 	}
 
 	public void addDraw(IndirectDraw draw) {
@@ -38,8 +45,17 @@ public class IndirectInstancer<I extends Instance> extends AbstractInstancer<I>
 		removeDeletedInstances();
 	}
 
-	public void upload(StagingBuffer stagingBuffer, long startPos, int dstVbo) {
-		if (shouldUploadAll(startPos)) {
+	public void writeModel(long ptr) {
+		MemoryUtil.memPutInt(ptr, 0); // instanceCount - to be incremented by the cull shader
+		MemoryUtil.memPutInt(ptr + 4, baseInstance); // baseInstance
+		MemoryUtil.memPutFloat(ptr + 8, boundingSphere.x()); // boundingSphere
+		MemoryUtil.memPutFloat(ptr + 12, boundingSphere.y());
+		MemoryUtil.memPutFloat(ptr + 16, boundingSphere.z());
+		MemoryUtil.memPutFloat(ptr + 20, boundingSphere.w());
+	}
+
+	public void uploadObjects(StagingBuffer stagingBuffer, long startPos, int dstVbo) {
+        if (shouldUploadAll(startPos)) {
 			uploadAll(stagingBuffer, startPos, dstVbo);
 		} else {
 			uploadChanged(stagingBuffer, startPos, dstVbo);
@@ -47,10 +63,11 @@ public class IndirectInstancer<I extends Instance> extends AbstractInstancer<I>
 
 		changed.clear();
 		lastStartPos = startPos;
+		lastModelIndex = index;
 	}
 
 	private boolean shouldUploadAll(long startPos) {
-		return startPos != lastStartPos;
+		return startPos != lastStartPos || index != lastModelIndex;
 	}
 
 	private void uploadChanged(StagingBuffer stagingBuffer, long baseByte, int dstVbo) {
@@ -81,11 +98,7 @@ public class IndirectInstancer<I extends Instance> extends AbstractInstancer<I>
 	}
 
 	private void writeOne(long ptr, I instance) {
-		MemoryUtil.memPutInt(ptr, modelIndex);
+		MemoryUtil.memPutInt(ptr, index);
 		writer.write(ptr + IndirectBuffers.INT_SIZE, instance);
 	}
-
-	public void setModelIndex(int modelIndex) {
-		this.modelIndex = modelIndex;
-	}
 }

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectMeshPool.java

@@ -1,182 +0,0 @@
-package com.jozufozu.flywheel.backend.engine.indirect;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-import org.jetbrains.annotations.Nullable;
-
-import com.jozufozu.flywheel.api.model.Mesh;
-import com.jozufozu.flywheel.api.vertex.VertexView;
-import com.jozufozu.flywheel.backend.InternalVertex;
-import com.jozufozu.flywheel.backend.gl.GlNumericType;
-import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
-import com.jozufozu.flywheel.backend.gl.buffer.GlBuffer;
-import com.jozufozu.flywheel.lib.memory.MemoryBlock;
-import com.jozufozu.flywheel.lib.model.QuadIndexSequence;
-
-public class IndirectMeshPool {
-	private final VertexView vertexView;
-	private final Map<Mesh, BufferedMesh> meshes = new HashMap<>();
-	private final List<BufferedMesh> meshList = new ArrayList<>();
-
-	private final GlVertexArray vertexArray;
-	private final GlBuffer vbo;
-	private final GlBuffer ebo;
-
-	private boolean dirty;
-
-	/**
-	 * Create a new mesh pool.
-	 */
-	public IndirectMeshPool() {
-		vertexView = InternalVertex.createVertexView();
-		vbo = new GlBuffer();
-		ebo = new GlBuffer();
-		vertexArray = GlVertexArray.create();
-
-		vertexArray.setElementBuffer(ebo.handle());
-		vertexArray.bindVertexBuffer(0, vbo.handle(), 0, InternalVertex.STRIDE);
-		vertexArray.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
-	}
-
-	/**
-	 * Allocate a model in the arena.
-	 *
-	 * @param mesh The model to allocate.
-	 * @return A handle to the allocated model.
-	 */
-	public BufferedMesh alloc(Mesh mesh) {
-		return meshes.computeIfAbsent(mesh, m -> {
-			BufferedMesh bufferedModel = new BufferedMesh(m);
-			meshList.add(bufferedModel);
-
-			dirty = true;
-			return bufferedModel;
-		});
-	}
-
-	@Nullable
-	public BufferedMesh get(Mesh mesh) {
-		return meshes.get(mesh);
-	}
-
-	public void flush() {
-		if (dirty) {
-			uploadAll();
-			dirty = false;
-		}
-	}
-
-	private void uploadAll() {
-		long neededSize = 0;
-		int maxQuadIndexCount = 0;
-		int nonQuadIndexCount = 0;
-		for (BufferedMesh mesh : meshList) {
-			neededSize += mesh.size();
-
-			if (mesh.mesh.indexSequence() == QuadIndexSequence.INSTANCE) {
-				maxQuadIndexCount = Math.max(maxQuadIndexCount, mesh.mesh.indexCount());
-			} else {
-				nonQuadIndexCount += mesh.mesh.indexCount();
-			}
-		}
-
-		final long totalIndexCount = maxQuadIndexCount + nonQuadIndexCount;
-
-		final var vertexBlock = MemoryBlock.malloc(neededSize);
-		final var indexBlock = MemoryBlock.malloc(totalIndexCount * GlNumericType.UINT.byteWidth());
-
-		final long vertexPtr = vertexBlock.ptr();
-		final long indexPtr = indexBlock.ptr();
-
-		int byteIndex = 0;
-		int baseVertex = 0;
-		int firstIndex = maxQuadIndexCount;
-		for (BufferedMesh mesh : meshList) {
-			mesh.byteIndex = byteIndex;
-			mesh.baseVertex = baseVertex;
-
-			mesh.write(vertexPtr, vertexView);
-
-			byteIndex += mesh.size();
-			baseVertex += mesh.vertexCount();
-
-			var indexFiller = mesh.mesh.indexSequence();
-			if (indexFiller == QuadIndexSequence.INSTANCE) {
-				mesh.firstIndex = 0;
-			} else {
-				var indexCount = mesh.mesh.indexCount();
-				mesh.firstIndex = firstIndex;
-				indexFiller.fill(indexPtr + (long) firstIndex * GlNumericType.UINT.byteWidth(), indexCount);
-
-				firstIndex += indexCount;
-			}
-		}
-
-		if (maxQuadIndexCount > 0) {
-			QuadIndexSequence.INSTANCE.fill(indexPtr, maxQuadIndexCount);
-		}
-
-		vbo.upload(vertexBlock);
-		ebo.upload(indexBlock);
-
-		vertexBlock.free();
-		indexBlock.free();
-	}
-
-	public void bindForDraw() {
-		vertexArray.bindForDraw();
-	}
-
-	public void delete() {
-		vertexArray.delete();
-		vbo.delete();
-		ebo.delete();
-		meshes.clear();
-		meshList.clear();
-	}
-
-	public static class BufferedMesh {
-		private final Mesh mesh;
-		private final int vertexCount;
-		private final int byteSize;
-
-		private long byteIndex;
-		private int baseVertex;
-		private int firstIndex;
-
-		private BufferedMesh(Mesh mesh) {
-			this.mesh = mesh;
-			vertexCount = mesh.vertexCount();
-			byteSize = vertexCount * InternalVertex.STRIDE;
-		}
-
-		public int vertexCount() {
-			return vertexCount;
-		}
-
-		public int size() {
-			return byteSize;
-		}
-
-		public int indexCount() {
-			return mesh.indexCount();
-		}
-
-		public int baseVertex() {
-			return baseVertex;
-		}
-
-		public int firstIndex() {
-			return firstIndex;
-		}
-
-		private void write(long ptr, VertexView vertexView) {
-			vertexView.ptr(ptr + byteIndex);
-			vertexView.vertexCount(vertexCount);
-			mesh.write(vertexView);
-		}
-	}
-}

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectModel.java

@@ -1,40 +0,0 @@
-package com.jozufozu.flywheel.backend.engine.indirect;
-
-import org.joml.Vector4fc;
-import org.lwjgl.system.MemoryUtil;
-
-public class IndirectModel {
-	public final IndirectInstancer<?> instancer;
-	public final int index;
-	private final Vector4fc boundingSphere;
-
-	private int baseInstance = -1;
-
-	public IndirectModel(IndirectInstancer<?> instancer, int index, Vector4fc boundingSphere) {
-		this.instancer = instancer;
-		this.index = index;
-		this.boundingSphere = boundingSphere;
-	}
-
-	public int baseInstance() {
-		return baseInstance;
-	}
-
-	public void prepare(int baseInstance) {
-		instancer.update();
-		this.baseInstance = baseInstance;
-	}
-
-	public void uploadObjects(StagingBuffer stagingBuffer, long start, int dstVbo) {
-		instancer.upload(stagingBuffer, start, dstVbo);
-	}
-
-	public void write(long ptr) {
-		MemoryUtil.memPutInt(ptr, 0); // instanceCount - to be incremented by the cull shader
-		MemoryUtil.memPutInt(ptr + 4, baseInstance); // baseInstance
-		MemoryUtil.memPutFloat(ptr + 8, boundingSphere.x()); // boundingSphere
-		MemoryUtil.memPutFloat(ptr + 12, boundingSphere.y());
-		MemoryUtil.memPutFloat(ptr + 16, boundingSphere.z());
-		MemoryUtil.memPutFloat(ptr + 20, boundingSphere.w());
-	}
-}

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/DrawCall.java

@@ -4,19 +4,20 @@ import org.jetbrains.annotations.Nullable;
 
 import com.jozufozu.flywheel.backend.InternalVertex;
 import com.jozufozu.flywheel.backend.engine.InstanceHandleImpl;
+import com.jozufozu.flywheel.backend.engine.MeshPool;
 import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
 
 public class DrawCall {
 	public final ShaderState shaderState;
 	private final InstancedInstancer<?> instancer;
-	private final InstancedMeshPool.BufferedMesh mesh;
+	private final MeshPool.BufferedMesh mesh;
 
 	private final GlVertexArray vao;
 	@Nullable
 	private GlVertexArray vaoScratch;
 	private boolean deleted;
 
-	public DrawCall(InstancedInstancer<?> instancer, InstancedMeshPool.BufferedMesh mesh, ShaderState shaderState) {
+	public DrawCall(InstancedInstancer<?> instancer, MeshPool.BufferedMesh mesh, ShaderState shaderState) {
 		this.instancer = instancer;
 		this.mesh = mesh;
 		this.shaderState = shaderState;
@@ -40,7 +41,7 @@ public class DrawCall {
 
 		vao.bindForDraw();
 
-		mesh.draw(instancer.getInstanceCount());
+		mesh.draw(instancer.instanceCount());
 	}
 
 	public void renderOne(InstanceHandleImpl impl) {
@@ -48,7 +49,7 @@ public class DrawCall {
 			return;
 		}
 
-		int instanceCount = instancer.getInstanceCount();
+		int instanceCount = instancer.instanceCount();
 		if (instanceCount <= 0 || impl.index >= instanceCount) {
 			return;
 		}

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancedDrawManager.java

@@ -12,17 +12,17 @@ import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.backend.engine.InstancerKey;
 import com.jozufozu.flywheel.backend.engine.InstancerStorage;
+import com.jozufozu.flywheel.backend.engine.MeshPool;
 
 public class InstancedDrawManager extends InstancerStorage<InstancedInstancer<?>> {
 	/**
 	 * The set of draw calls to make in each {@link RenderStage}.
 	 */
 	private final Map<RenderStage, DrawSet> drawSets = new EnumMap<>(RenderStage.class);
-	private final EboCache eboCache = new EboCache();
 	/**
 	 * A map of vertex types to their mesh pools.
 	 */
-	private final InstancedMeshPool meshPool = new InstancedMeshPool(eboCache);
+	private final MeshPool meshPool = new MeshPool();
 
 	public DrawSet get(RenderStage stage) {
 		return drawSets.getOrDefault(stage, DrawSet.EMPTY);
@@ -36,7 +36,7 @@ public class InstancedDrawManager extends InstancerStorage<InstancedInstancer<?>
 			// Update the instancers and remove any that are empty.
 			instancer.update();
 
-			if (instancer.getInstanceCount() == 0) {
+			if (instancer.instanceCount() == 0) {
 				instancer.delete();
 				return true;
 			} else {
@@ -63,8 +63,6 @@ public class InstancedDrawManager extends InstancerStorage<InstancedInstancer<?>
 		drawSets.values()
 				.forEach(DrawSet::delete);
 		drawSets.clear();
-
-		eboCache.invalidate();
 	}
 
 	@Override

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancedMeshPool.java

@@ -1,205 +0,0 @@
-package com.jozufozu.flywheel.backend.engine.instancing;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-
-import org.jetbrains.annotations.Nullable;
-import org.lwjgl.opengl.GL32;
-
-import com.jozufozu.flywheel.Flywheel;
-import com.jozufozu.flywheel.api.model.Mesh;
-import com.jozufozu.flywheel.api.vertex.VertexView;
-import com.jozufozu.flywheel.backend.InternalVertex;
-import com.jozufozu.flywheel.backend.gl.GlPrimitive;
-import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
-import com.jozufozu.flywheel.backend.gl.buffer.GlBuffer;
-import com.jozufozu.flywheel.backend.gl.buffer.MappedBuffer;
-
-public class InstancedMeshPool {
-	private final VertexView vertexView;
-	private final Map<Mesh, BufferedMesh> byMesh = new HashMap<>();
-	private final List<BufferedMesh> ordered = new ArrayList<>();
-
-	private final GlBuffer vbo;
-	private final EboCache eboCache;
-	private long byteSize;
-
-	private boolean dirty;
-	private boolean anyToRemove;
-
-	/**
-	 * Create a new mesh pool.
-	 */
-	public InstancedMeshPool(EboCache eboCache) {
-		this.eboCache = eboCache;
-		vertexView = InternalVertex.createVertexView();
-        vbo = new GlBuffer();
-		vbo.growthFunction(l -> Math.max(l + InternalVertex.STRIDE * 128L, (long) (l * 1.6)));
-	}
-
-	/**
-	 * Allocate a mesh in the arena.
-	 *
-	 * @param mesh     The mesh to allocate.
-	 * @return A handle to the allocated mesh.
-	 */
-	public BufferedMesh alloc(Mesh mesh) {
-		return byMesh.computeIfAbsent(mesh, this::_alloc);
-	}
-
-	private BufferedMesh _alloc(Mesh m) {
-		BufferedMesh bufferedMesh = new BufferedMesh(m, this.eboCache);
-		ordered.add(bufferedMesh);
-
-		dirty = true;
-		return bufferedMesh;
-	}
-
-	@Nullable
-	public BufferedMesh get(Mesh mesh) {
-		return byMesh.get(mesh);
-	}
-
-	public void flush() {
-		if (!dirty) {
-			return;
-		}
-
-		if (anyToRemove) {
-			anyToRemove = false;
-			processDeletions();
-		}
-
-		var forUpload = calculateByteSizeAndGetMeshesForUpload();
-
-		if (!forUpload.isEmpty()) {
-			vbo.ensureCapacity(byteSize);
-
-			upload(forUpload);
-		}
-
-		dirty = false;
-	}
-
-	private void processDeletions() {
-		// remove deleted meshes
-		ordered.removeIf(bufferedMesh -> {
-			boolean deleted = bufferedMesh.deleted();
-			if (deleted) {
-				byMesh.remove(bufferedMesh.mesh);
-			}
-			return deleted;
-		});
-	}
-
-	private List<BufferedMesh> calculateByteSizeAndGetMeshesForUpload() {
-		List<BufferedMesh> out = new ArrayList<>();
-
-		long byteIndex = 0;
-		for (BufferedMesh mesh : ordered) {
-			if (mesh.byteIndex != byteIndex) {
-				out.add(mesh);
-			}
-
-			mesh.byteIndex = byteIndex;
-
-			byteIndex += mesh.byteSize;
-		}
-
-		this.byteSize = byteIndex;
-
-		return out;
-	}
-
-	private void upload(List<BufferedMesh> meshes) {
-		try (MappedBuffer mapped = vbo.map()) {
-			long ptr = mapped.ptr();
-
-			for (BufferedMesh mesh : meshes) {
-				mesh.write(ptr, vertexView);
-				mesh.boundTo.clear();
-			}
-		} catch (Exception e) {
-			Flywheel.LOGGER.error("Error uploading pooled meshes:", e);
-		}
-	}
-
-	public void delete() {
-		vbo.delete();
-		byMesh.clear();
-		ordered.clear();
-	}
-
-	@Override
-	public String toString() {
-		return "InstancedMeshPool{" + "byteSize=" + byteSize + ", meshCount=" + byMesh.size() + '}';
-	}
-
-	public class BufferedMesh {
-		private final Mesh mesh;
-		private final int vertexCount;
-		private final int byteSize;
-		private final int ebo;
-
-		private long byteIndex = -1;
-		private int referenceCount = 0;
-
-		private final Set<GlVertexArray> boundTo = new HashSet<>();
-
-		private BufferedMesh(Mesh mesh, EboCache eboCache) {
-			this.mesh = mesh;
-			vertexCount = mesh.vertexCount();
-			byteSize = vertexCount * InternalVertex.STRIDE;
-			this.ebo = eboCache.get(mesh.indexSequence(), mesh.indexCount());
-		}
-
-		public boolean deleted() {
-			return referenceCount <= 0;
-		}
-
-		public boolean invalid() {
-			return mesh.vertexCount() == 0 || deleted() || byteIndex == -1;
-		}
-
-		private void write(long ptr, VertexView vertexView) {
-			if (invalid()) {
-				return;
-			}
-
-			vertexView.ptr(ptr + byteIndex);
-			vertexView.vertexCount(vertexCount);
-			mesh.write(vertexView);
-		}
-
-		public void setup(GlVertexArray vao) {
-			if (boundTo.add(vao)) {
-				vao.bindVertexBuffer(0, InstancedMeshPool.this.vbo.handle(), byteIndex, InternalVertex.STRIDE);
-				vao.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
-				vao.setElementBuffer(ebo);
-			}
-		}
-
-		public void draw(int instanceCount) {
-			if (instanceCount > 1) {
-				GL32.glDrawElementsInstanced(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, 0, instanceCount);
-			} else {
-				GL32.glDrawElements(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, 0);
-			}
-		}
-
-		public void acquire() {
-			referenceCount++;
-		}
-
-		public void drop() {
-			if (--referenceCount == 0) {
-				InstancedMeshPool.this.dirty = true;
-				InstancedMeshPool.this.anyToRemove = true;
-			}
-		}
-	}
-}

src/main/resources/assets/flywheel/flywheel/internal/indirect/apply.glsl

@@ -22,5 +22,4 @@ void main() {
 
     uint modelIndex = drawCommands[drawIndex].modelIndex;
     drawCommands[drawIndex].instanceCount = models[modelIndex].instanceCount;
-    drawCommands[drawIndex].baseInstance = models[modelIndex].baseInstance;
 }