Burning a house to kill a spider

- Fix garbage indices on instancing engine
- glDrawElements* wants indices as a byte offset, we were giving it
  a word offset
- Rename BufferedMesh -> PooledMesh
- PooledMesh no longer stores things it can fetch from the inner mesh
- Use one vao for all drawcalls in instancing engine
- PooledMesh issues *BaseVertex calls
- Move crumbling logic into InstancedDrawManager
- Move programs acquisition into InstancedDrawManager
- Move owned gl objects into InstancedDrawManager

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

@@ -1,7 +1,6 @@
 package com.jozufozu.flywheel.backend.engine;
 
 import com.jozufozu.flywheel.api.model.IndexSequence;
-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;
@@ -60,7 +59,7 @@ public class IndexPool {
 			totalIndexCount += count;
 		}
 
-		final var indexBlock = MemoryBlock.malloc(totalIndexCount * GlNumericType.UINT.byteWidth());
+		final var indexBlock = MemoryBlock.malloc(totalIndexCount * Integer.BYTES);
 		final long indexPtr = indexBlock.ptr();
 
 		int firstIndex = 0;
@@ -70,7 +69,7 @@ public class IndexPool {
 
 			firstIndices.put(indexSequence, firstIndex);
 
-			indexSequence.fill(indexPtr + (long) firstIndex * GlNumericType.UINT.byteWidth(), indexCount);
+			indexSequence.fill(indexPtr + (long) firstIndex * Integer.BYTES, indexCount);
 
 			firstIndex += indexCount;
 		}

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

@@ -4,7 +4,6 @@ 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;
@@ -17,13 +16,11 @@ 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.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 List<BufferedMesh> recentlyAllocated = new ArrayList<>();
+	private final Map<Mesh, PooledMesh> meshes = new HashMap<>();
+	private final List<PooledMesh> meshList = new ArrayList<>();
+	private final List<PooledMesh> recentlyAllocated = new ArrayList<>();
 
 	private final GlBuffer vbo;
 	private final IndexPool indexPool;
@@ -46,12 +43,12 @@ public class MeshPool {
 	 * @param mesh The model to allocate.
 	 * @return A handle to the allocated model.
 	 */
-	public BufferedMesh alloc(Mesh mesh) {
+	public PooledMesh alloc(Mesh mesh) {
 		return meshes.computeIfAbsent(mesh, this::_alloc);
 	}
 
-	private BufferedMesh _alloc(Mesh m) {
-		BufferedMesh bufferedModel = new BufferedMesh(m);
+	private PooledMesh _alloc(Mesh m) {
+		PooledMesh bufferedModel = new PooledMesh(m);
 		meshList.add(bufferedModel);
 		recentlyAllocated.add(bufferedModel);
 
@@ -60,7 +57,7 @@ public class MeshPool {
 	}
 
 	@Nullable
-	public BufferedMesh get(Mesh mesh) {
+	public MeshPool.PooledMesh get(Mesh mesh) {
 		return meshes.get(mesh);
 	}
 
@@ -75,14 +72,15 @@ public class MeshPool {
 
 			// Might want to shrink the index pool if something was removed.
 			indexPool.reset();
-			for (BufferedMesh mesh : meshList) {
+			for (PooledMesh mesh : meshList) {
 				indexPool.updateCount(mesh.mesh.indexSequence(), mesh.indexCount());
 			}
 		} else {
 			// Otherwise, just update the index with the new counts.
-			for (BufferedMesh mesh : recentlyAllocated) {
+			for (PooledMesh mesh : recentlyAllocated) {
 				indexPool.updateCount(mesh.mesh.indexSequence(), mesh.indexCount());
 			}
+			recentlyAllocated.clear();
 		}
 
 		// Always need to flush the index pool.
@@ -94,10 +92,10 @@ public class MeshPool {
 
 	private void processDeletions() {
 		// remove deleted meshes
-		meshList.removeIf(bufferedMesh -> {
-			boolean deleted = bufferedMesh.deleted();
+		meshList.removeIf(pooledMesh -> {
+			boolean deleted = pooledMesh.deleted();
 			if (deleted) {
-				meshes.remove(bufferedMesh.mesh);
+				meshes.remove(pooledMesh.mesh);
 			}
 			return deleted;
 		});
@@ -105,7 +103,7 @@ public class MeshPool {
 
 	private void uploadAll() {
 		long neededSize = 0;
-		for (BufferedMesh mesh : meshList) {
+		for (PooledMesh mesh : meshList) {
 			neededSize += mesh.byteSize();
 		}
 
@@ -114,18 +112,15 @@ public class MeshPool {
 
 		int byteIndex = 0;
 		int baseVertex = 0;
-		for (BufferedMesh mesh : meshList) {
-			mesh.byteIndex = byteIndex;
+		for (PooledMesh mesh : meshList) {
 			mesh.baseVertex = baseVertex;
 
-			vertexView.ptr(vertexPtr + mesh.byteIndex);
-			vertexView.vertexCount(mesh.vertexCount);
+			vertexView.ptr(vertexPtr + byteIndex);
+			vertexView.vertexCount(mesh.vertexCount());
 			mesh.mesh.write(vertexView);
 
 			byteIndex += mesh.byteSize();
 			baseVertex += mesh.vertexCount();
-
-			mesh.boundTo.clear();
 		}
 
 		vbo.upload(vertexBlock);
@@ -146,29 +141,24 @@ public class MeshPool {
 		meshList.clear();
 	}
 
-	public class BufferedMesh {
+	public class PooledMesh {
+		public static final int INVALID_BASE_VERTEX = -1;
 		private final Mesh mesh;
-		private final int vertexCount;
-		private final int byteSize;
 
-		private long byteIndex;
-		private int baseVertex;
+		private int baseVertex = INVALID_BASE_VERTEX;
 
 		private int referenceCount = 0;
-		private final Set<GlVertexArray> boundTo = new ReferenceArraySet<>();
 
-		private BufferedMesh(Mesh mesh) {
+		private PooledMesh(Mesh mesh) {
 			this.mesh = mesh;
-			vertexCount = mesh.vertexCount();
-			byteSize = vertexCount * InternalVertex.STRIDE;
 		}
 
 		public int vertexCount() {
-			return vertexCount;
+			return mesh.vertexCount();
 		}
 
 		public int byteSize() {
-			return byteSize;
+			return mesh.vertexCount() * InternalVertex.STRIDE;
 		}
 
 		public int indexCount() {
@@ -180,7 +170,11 @@ public class MeshPool {
 		}
 
 		public int firstIndex() {
-			return indexPool.firstIndex(mesh.indexSequence());
+			return MeshPool.this.indexPool.firstIndex(mesh.indexSequence());
+		}
+
+		public long firstIndexByteOffset() {
+			return (long) firstIndex() * Integer.BYTES;
 		}
 
 		public boolean deleted() {
@@ -188,31 +182,22 @@ public class MeshPool {
 		}
 
 		public boolean invalid() {
-			return mesh.vertexCount() == 0 || deleted() || byteIndex == -1;
+			return mesh.vertexCount() == 0 || baseVertex == INVALID_BASE_VERTEX || deleted();
 		}
 
 		public void draw(int instanceCount) {
 			if (instanceCount > 1) {
-				GL32.glDrawElementsInstanced(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, firstIndex(), instanceCount);
+				GL32.glDrawElementsInstancedBaseVertex(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, firstIndexByteOffset(), instanceCount, baseVertex);
 			} else {
-				GL32.glDrawElements(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, firstIndex());
+				GL32.glDrawElementsBaseVertex(GlPrimitive.TRIANGLES.glEnum, mesh.indexCount(), GL32.GL_UNSIGNED_INT, firstIndexByteOffset(), baseVertex);
 			}
 		}
 
-		public void setup(GlVertexArray vao) {
-            if (!boundTo.add(vao)) {
-                return;
-            }
-            MeshPool.this.indexPool.bind(vao);
-            vao.bindVertexBuffer(0, MeshPool.this.vbo.handle(), byteIndex, InternalVertex.STRIDE);
-            vao.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
-        }
-
 		public void acquire() {
 			referenceCount++;
 		}
 
-		public void drop() {
+		public void release() {
 			if (--referenceCount == 0) {
 				MeshPool.this.dirty = true;
 				MeshPool.this.anyToRemove = true;

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

@@ -182,8 +182,8 @@ public class IndirectCullingGroup<I extends Instance> {
 		instancers.add(instancer);
 
 		for (var entry : model.meshes()) {
-			MeshPool.BufferedMesh bufferedMesh = meshPool.alloc(entry.mesh());
-			var draw = new IndirectDraw(instancer, entry.material(), bufferedMesh, stage);
+			MeshPool.PooledMesh pooledMesh = meshPool.alloc(entry.mesh());
+			var draw = new IndirectDraw(instancer, entry.material(), pooledMesh, stage);
 			indirectDraws.add(draw);
 			instancer.addDraw(draw);
 		}

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

@@ -11,7 +11,7 @@ import com.jozufozu.flywheel.backend.engine.MeshPool;
 public class IndirectDraw {
 	private final IndirectInstancer<?> model;
 	private final Material material;
-	private final MeshPool.BufferedMesh mesh;
+	private final MeshPool.PooledMesh mesh;
 	private final RenderStage stage;
 
 	private final int materialVertexIndex;
@@ -20,7 +20,7 @@ public class IndirectDraw {
 	private final int packedMaterialProperties;
 	private boolean deleted;
 
-	public IndirectDraw(IndirectInstancer<?> model, Material material, MeshPool.BufferedMesh mesh, RenderStage stage) {
+	public IndirectDraw(IndirectInstancer<?> model, Material material, MeshPool.PooledMesh mesh, RenderStage stage) {
 		this.model = model;
 		this.material = material;
 		this.mesh = mesh;
@@ -42,7 +42,7 @@ public class IndirectDraw {
 		return material;
 	}
 
-	public MeshPool.BufferedMesh mesh() {
+	public MeshPool.PooledMesh mesh() {
 		return mesh;
 	}
 
@@ -85,7 +85,7 @@ public class IndirectDraw {
 			return;
 		}
 
-		mesh.drop();
+		mesh.release();
 
 		deleted = true;
 	}

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

@@ -1,30 +1,22 @@
 package com.jozufozu.flywheel.backend.engine.instancing;
 
-import org.jetbrains.annotations.Nullable;
-
 import com.jozufozu.flywheel.backend.engine.InstanceHandleImpl;
 import com.jozufozu.flywheel.backend.engine.MeshPool;
 import com.jozufozu.flywheel.backend.gl.TextureBuffer;
-import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
 
 public class DrawCall {
 	public final ShaderState shaderState;
 	private final InstancedInstancer<?> instancer;
-	private final MeshPool.BufferedMesh mesh;
+	private final MeshPool.PooledMesh mesh;
 
-	private final GlVertexArray vao;
-	@Nullable
-	private GlVertexArray vaoScratch;
 	private boolean deleted;
 
-	public DrawCall(InstancedInstancer<?> instancer, MeshPool.BufferedMesh mesh, ShaderState shaderState) {
+	public DrawCall(InstancedInstancer<?> instancer, MeshPool.PooledMesh mesh, ShaderState shaderState) {
 		this.instancer = instancer;
 		this.mesh = mesh;
 		this.shaderState = shaderState;
 
 		mesh.acquire();
-
-		vao = GlVertexArray.create();
 	}
 
 	public boolean deleted() {
@@ -37,9 +29,6 @@ public class DrawCall {
 		}
 
 		instancer.bind(buffer);
-		mesh.setup(vao);
-
-		vao.bindForDraw();
 
 		mesh.draw(instancer.instanceCount());
 	}
@@ -54,36 +43,17 @@ public class DrawCall {
 			return;
 		}
 
-		var vao = lazyScratchVao();
-
 		instancer.bind(buffer);
-		mesh.setup(vao);
-
-		vao.bindForDraw();
 
 		mesh.draw(1);
 	}
 
-	private GlVertexArray lazyScratchVao() {
-		if (vaoScratch == null) {
-			vaoScratch = GlVertexArray.create();
-		}
-		return vaoScratch;
-	}
-
 	public void delete() {
 		if (deleted) {
 			return;
 		}
 
-		vao.delete();
-
-		if (vaoScratch != null) {
-			vaoScratch.delete();
-			vaoScratch = null;
-		}
-
-		mesh.drop();
+		mesh.release();
 
 		deleted = true;
 	}

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

@@ -1,119 +0,0 @@
-package com.jozufozu.flywheel.backend.engine.instancing;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.function.Consumer;
-
-import com.jozufozu.flywheel.api.backend.Engine;
-import com.jozufozu.flywheel.api.context.TextureSource;
-import com.jozufozu.flywheel.api.instance.Instance;
-import com.jozufozu.flywheel.backend.compile.InstancingPrograms;
-import com.jozufozu.flywheel.backend.engine.CommonCrumbling;
-import com.jozufozu.flywheel.backend.engine.InstanceHandleImpl;
-import com.jozufozu.flywheel.backend.engine.MaterialRenderState;
-import com.jozufozu.flywheel.backend.engine.textures.TextureBinder;
-import com.jozufozu.flywheel.backend.engine.uniform.Uniforms;
-import com.jozufozu.flywheel.backend.gl.GlStateTracker;
-import com.jozufozu.flywheel.backend.gl.GlTextureUnit;
-import com.jozufozu.flywheel.backend.gl.TextureBuffer;
-import com.jozufozu.flywheel.lib.context.ContextShaders;
-import com.jozufozu.flywheel.lib.context.Contexts;
-import com.jozufozu.flywheel.lib.material.SimpleMaterial;
-
-import it.unimi.dsi.fastutil.ints.Int2ObjectArrayMap;
-import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
-import net.minecraft.client.resources.model.ModelBakery;
-
-public class InstancedCrumbling {
-	public static void render(List<Engine.CrumblingBlock> crumblingBlocks, InstancingPrograms programs, TextureSource textureSource, TextureBuffer instanceTexture) {
-		// Sort draw calls into buckets, so we don't have to do as many shader binds.
-		var byShaderState = doCrumblingSort(crumblingBlocks);
-
-		if (byShaderState.isEmpty()) {
-			return;
-		}
-
-		var crumblingMaterial = SimpleMaterial.builder();
-
-		try (var state = GlStateTracker.getRestoreState()) {
-			TextureBinder.bindLightAndOverlay();
-
-			for (var shaderStateEntry : byShaderState.entrySet()) {
-				var byProgress = shaderStateEntry.getValue();
-
-				if (byProgress.isEmpty()) {
-					continue;
-				}
-
-				ShaderState shader = shaderStateEntry.getKey();
-
-				CommonCrumbling.applyCrumblingProperties(crumblingMaterial, shader.material());
-
-				var program = programs.get(shader.instanceType(), ContextShaders.CRUMBLING);
-				program.bind();
-
-				Uniforms.bindForDraw();
-				InstancingEngine.uploadMaterialUniform(program, crumblingMaterial);
-
-				MaterialRenderState.setup(crumblingMaterial);
-
-				for (var progressEntry : byProgress.int2ObjectEntrySet()) {
-					var drawCalls = progressEntry.getValue();
-
-					if (drawCalls.isEmpty()) {
-						continue;
-					}
-
-					var context = Contexts.CRUMBLING.get(progressEntry.getIntKey());
-					context.prepare(crumblingMaterial, program, textureSource);
-
-					GlTextureUnit.T3.makeActive();
-					program.setSamplerBinding("_flw_instances", 3);
-
-					for (Consumer<TextureBuffer> drawCall : drawCalls) {
-                        drawCall.accept(instanceTexture);
-                    }
-
-                    TextureBinder.resetTextureBindings();
-				}
-			}
-
-			MaterialRenderState.reset();
-			TextureBinder.resetLightAndOverlay();
-		}
-	}
-
-	private static Map<ShaderState, Int2ObjectMap<List<Consumer<TextureBuffer>>>> doCrumblingSort(List<Engine.CrumblingBlock> instances) {
-		Map<ShaderState, Int2ObjectMap<List<Consumer<TextureBuffer>>>> out = new HashMap<>();
-
-		for (Engine.CrumblingBlock triple : instances) {
-			int progress = triple.progress();
-
-			if (progress < 0 || progress >= ModelBakery.DESTROY_TYPES.size()) {
-				continue;
-			}
-
-			for (Instance instance : triple.instances()) {
-				// Filter out instances that weren't created by this engine.
-				// If all is well, we probably shouldn't take the `continue`
-				// branches but better to do checked casts.
-				if (!(instance.handle() instanceof InstanceHandleImpl impl)) {
-					continue;
-				}
-				if (!(impl.instancer instanceof InstancedInstancer<?> instancer)) {
-					continue;
-				}
-
-                for (DrawCall draw : instancer.drawCalls()) {
-					out.computeIfAbsent(draw.shaderState, $ -> new Int2ObjectArrayMap<>())
-							.computeIfAbsent(progress, $ -> new ArrayList<>())
-							.add(buf -> draw.renderOne(buf, impl));
-				}
-			}
-		}
-
-		return out;
-	}
-}

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

@@ -1,31 +1,72 @@
 package com.jozufozu.flywheel.backend.engine.instancing;
 
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.EnumMap;
+import java.util.HashMap;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
+import java.util.function.Consumer;
+
+import org.lwjgl.opengl.GL32;
 
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ListMultimap;
+import com.jozufozu.flywheel.api.backend.Engine;
 import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.instance.Instance;
+import com.jozufozu.flywheel.api.material.Material;
+import com.jozufozu.flywheel.backend.ShaderIndices;
+import com.jozufozu.flywheel.backend.compile.InstancingPrograms;
+import com.jozufozu.flywheel.backend.engine.CommonCrumbling;
+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.MaterialEncoder;
+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.GlTextureUnit;
+import com.jozufozu.flywheel.backend.gl.TextureBuffer;
+import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
+import com.jozufozu.flywheel.backend.gl.shader.GlProgram;
+import com.jozufozu.flywheel.lib.context.ContextShaders;
+import com.jozufozu.flywheel.lib.context.Contexts;
+import com.jozufozu.flywheel.lib.material.SimpleMaterial;
+
+import it.unimi.dsi.fastutil.ints.Int2ObjectArrayMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import net.minecraft.client.resources.model.ModelBakery;
 
 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 InstancingPrograms programs;
 	/**
 	 * A map of vertex types to their mesh pools.
 	 */
-	private final MeshPool meshPool = new MeshPool();
+	private final MeshPool meshPool;
+	private final GlVertexArray vao;
+	private final TextureSourceImpl textures;
+	private final TextureBuffer instanceTexture;
 
-	public DrawSet get(RenderStage stage) {
-		return drawSets.getOrDefault(stage, DrawSet.EMPTY);
+	public InstancedDrawManager(InstancingPrograms programs) {
+		programs.acquire();
+		this.programs = programs;
+
+		meshPool = new MeshPool();
+		vao = GlVertexArray.create();
+		textures = new TextureSourceImpl();
+		instanceTexture = new TextureBuffer();
+
+		meshPool.bind(vao);
 	}
 
 	public void flush() {
@@ -52,17 +93,70 @@ public class InstancedDrawManager extends InstancerStorage<InstancedInstancer<?>
 		meshPool.flush();
 	}
 
+	public void renderStage(RenderStage stage) {
+		var drawSet = drawSets.getOrDefault(stage, DrawSet.EMPTY);
+
+		if (drawSet.isEmpty()) {
+			return;
+		}
+
+		try (var state = GlStateTracker.getRestoreState()) {
+			render(drawSet);
+		}
+	}
+
 	public void delete() {
 		instancers.values()
 				.forEach(InstancedInstancer::delete);
 
-		super.delete();
-
-		meshPool.delete();
-
 		drawSets.values()
 				.forEach(DrawSet::delete);
 		drawSets.clear();
+
+		meshPool.delete();
+		instanceTexture.delete();
+		programs.release();
+		vao.delete();
+
+		super.delete();
+	}
+
+	private void render(InstancedDrawManager.DrawSet drawSet) {
+		Uniforms.bindForDraw();
+		vao.bindForDraw();
+		TextureBinder.bindLightAndOverlay();
+
+		for (var entry : drawSet) {
+			var shader = entry.getKey();
+			var drawCalls = entry.getValue();
+
+			if (drawCalls.isEmpty()) {
+				continue;
+			}
+
+			var context = shader.context();
+			var material = shader.material();
+
+			var program = programs.get(shader.instanceType(), context.contextShader());
+			program.bind();
+
+			uploadMaterialUniform(program, material);
+
+			context.prepare(material, program, textures);
+			MaterialRenderState.setup(material);
+
+			GlTextureUnit.T3.makeActive();
+
+			program.setSamplerBinding("_flw_instances", 3);
+
+			for (var drawCall : drawCalls) {
+				drawCall.render(instanceTexture);
+			}
+			TextureBinder.resetTextureBindings();
+		}
+
+		MaterialRenderState.reset();
+		TextureBinder.resetLightAndOverlay();
 	}
 
 	@Override
@@ -89,6 +183,106 @@ public class InstancedDrawManager extends InstancerStorage<InstancedInstancer<?>
 		}
 	}
 
+	public void renderCrumbling(List<Engine.CrumblingBlock> crumblingBlocks) {
+		// Sort draw calls into buckets, so we don't have to do as many shader binds.
+		var byShaderState = doCrumblingSort(crumblingBlocks);
+
+		if (byShaderState.isEmpty()) {
+			return;
+		}
+
+		var crumblingMaterial = SimpleMaterial.builder();
+
+		try (var state = GlStateTracker.getRestoreState()) {
+			Uniforms.bindForDraw();
+			vao.bindForDraw();
+			TextureBinder.bindLightAndOverlay();
+
+			for (var shaderStateEntry : byShaderState.entrySet()) {
+				var byProgress = shaderStateEntry.getValue();
+
+				if (byProgress.isEmpty()) {
+					continue;
+				}
+
+				ShaderState shader = shaderStateEntry.getKey();
+
+				CommonCrumbling.applyCrumblingProperties(crumblingMaterial, shader.material());
+
+				var program = programs.get(shader.instanceType(), ContextShaders.CRUMBLING);
+				program.bind();
+
+				uploadMaterialUniform(program, crumblingMaterial);
+
+				MaterialRenderState.setup(crumblingMaterial);
+
+				for (var progressEntry : byProgress.int2ObjectEntrySet()) {
+					var drawCalls = progressEntry.getValue();
+
+					if (drawCalls.isEmpty()) {
+						continue;
+					}
+
+					var context = Contexts.CRUMBLING.get(progressEntry.getIntKey());
+					context.prepare(crumblingMaterial, program, textures);
+
+					GlTextureUnit.T3.makeActive();
+					program.setSamplerBinding("_flw_instances", 3);
+
+					for (Consumer<TextureBuffer> drawCall : drawCalls) {
+						drawCall.accept(instanceTexture);
+					}
+
+					TextureBinder.resetTextureBindings();
+				}
+			}
+
+			MaterialRenderState.reset();
+			TextureBinder.resetLightAndOverlay();
+		}
+	}
+
+	private static Map<ShaderState, Int2ObjectMap<List<Consumer<TextureBuffer>>>> doCrumblingSort(List<Engine.CrumblingBlock> instances) {
+		Map<ShaderState, Int2ObjectMap<List<Consumer<TextureBuffer>>>> out = new HashMap<>();
+
+		for (Engine.CrumblingBlock triple : instances) {
+			int progress = triple.progress();
+
+			if (progress < 0 || progress >= ModelBakery.DESTROY_TYPES.size()) {
+				continue;
+			}
+
+			for (Instance instance : triple.instances()) {
+				// Filter out instances that weren't created by this engine.
+				// If all is well, we probably shouldn't take the `continue`
+				// branches but better to do checked casts.
+				if (!(instance.handle() instanceof InstanceHandleImpl impl)) {
+					continue;
+				}
+				if (!(impl.instancer instanceof InstancedInstancer<?> instancer)) {
+					continue;
+				}
+
+				for (DrawCall draw : instancer.drawCalls()) {
+					out.computeIfAbsent(draw.shaderState, $ -> new Int2ObjectArrayMap<>())
+							.computeIfAbsent(progress, $ -> new ArrayList<>())
+							.add(buf -> draw.renderOne(buf, impl));
+				}
+			}
+		}
+
+		return out;
+	}
+
+	public static void uploadMaterialUniform(GlProgram program, Material material) {
+		int uniformLocation = program.getUniformLocation("_flw_packedMaterial");
+		int vertexIndex = ShaderIndices.getVertexShaderIndex(material.shaders());
+		int fragmentIndex = ShaderIndices.getFragmentShaderIndex(material.shaders());
+		int packedFogAndCutout = MaterialEncoder.packFogAndCutout(material);
+		int packedMaterialProperties = MaterialEncoder.packProperties(material);
+		GL32.glUniform4ui(uniformLocation, vertexIndex, fragmentIndex, packedFogAndCutout, packedMaterialProperties);
+	}
+
 	public static class DrawSet implements Iterable<Map.Entry<ShaderState, Collection<DrawCall>>> {
 		public static final DrawSet EMPTY = new DrawSet(ImmutableListMultimap.of());
 

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

@@ -2,42 +2,27 @@ package com.jozufozu.flywheel.backend.engine.instancing;
 
 import java.util.List;
 
-import org.lwjgl.opengl.GL32;
-
 import com.jozufozu.flywheel.api.event.RenderContext;
 import com.jozufozu.flywheel.api.event.RenderStage;
-import com.jozufozu.flywheel.api.material.Material;
 import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
-import com.jozufozu.flywheel.backend.ShaderIndices;
 import com.jozufozu.flywheel.backend.compile.InstancingPrograms;
 import com.jozufozu.flywheel.backend.engine.AbstractEngine;
 import com.jozufozu.flywheel.backend.engine.AbstractInstancer;
 import com.jozufozu.flywheel.backend.engine.InstancerStorage;
-import com.jozufozu.flywheel.backend.engine.MaterialEncoder;
-import com.jozufozu.flywheel.backend.engine.MaterialRenderState;
-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.GlTextureUnit;
-import com.jozufozu.flywheel.backend.gl.TextureBuffer;
-import com.jozufozu.flywheel.backend.gl.shader.GlProgram;
 import com.jozufozu.flywheel.lib.task.Flag;
 import com.jozufozu.flywheel.lib.task.NamedFlag;
 import com.jozufozu.flywheel.lib.task.SyncedPlan;
 
 public class InstancingEngine extends AbstractEngine {
-	private final InstancingPrograms programs;
-	private final TextureSourceImpl textures = new TextureSourceImpl();
-	private final TextureBuffer instanceTexture = new TextureBuffer();
-	private final InstancedDrawManager drawManager = new InstancedDrawManager();
+	private final InstancedDrawManager drawManager;
 	private final Flag flushFlag = new NamedFlag("flushed");
 
 	public InstancingEngine(InstancingPrograms programs, int maxOriginDistance) {
 		super(maxOriginDistance);
-		programs.acquire();
-		this.programs = programs;
+        drawManager = new InstancedDrawManager(programs);
     }
 
 	@Override
@@ -60,16 +45,7 @@ public class InstancingEngine extends AbstractEngine {
 			flushFlag.lower();
 		}
 
-		var drawSet = drawManager.get(stage);
-
-		if (drawSet.isEmpty()) {
-			return;
-		}
-
-		try (var state = GlStateTracker.getRestoreState()) {
-			Uniforms.bindForDraw();
-			render(drawSet);
-		}
+		drawManager.renderStage(stage);
 	}
 
 	@Override
@@ -77,7 +53,7 @@ public class InstancingEngine extends AbstractEngine {
 		// Need to wait for flush before we can inspect instancer state.
 		executor.syncUntil(flushFlag::isRaised);
 
-		InstancedCrumbling.render(crumblingBlocks, programs, textures, instanceTexture);
+		drawManager.renderCrumbling(crumblingBlocks);
 	}
 
 	@Override
@@ -88,52 +64,5 @@ public class InstancingEngine extends AbstractEngine {
 	@Override
 	public void delete() {
 		drawManager.delete();
-		programs.release();
-		instanceTexture.delete();
-	}
-
-	private void render(InstancedDrawManager.DrawSet drawSet) {
-		TextureBinder.bindLightAndOverlay();
-
-		for (var entry : drawSet) {
-			var shader = entry.getKey();
-			var drawCalls = entry.getValue();
-
-			if (drawCalls.isEmpty()) {
-				continue;
-			}
-
-			var context = shader.context();
-			var material = shader.material();
-
-			var program = programs.get(shader.instanceType(), context.contextShader());
-			program.bind();
-
-			uploadMaterialUniform(program, material);
-
-			context.prepare(material, program, textures);
-			MaterialRenderState.setup(material);
-
-			GlTextureUnit.T3.makeActive();
-
-			program.setSamplerBinding("_flw_instances", 3);
-
-			for (var drawCall : drawCalls) {
-				drawCall.render(instanceTexture);
-			}
-			TextureBinder.resetTextureBindings();
-		}
-
-		MaterialRenderState.reset();
-		TextureBinder.resetLightAndOverlay();
-	}
-
-	public static void uploadMaterialUniform(GlProgram program, Material material) {
-		int uniformLocation = program.getUniformLocation("_flw_packedMaterial");
-		int vertexIndex = ShaderIndices.getVertexShaderIndex(material.shaders());
-		int fragmentIndex = ShaderIndices.getFragmentShaderIndex(material.shaders());
-		int packedFogAndCutout = MaterialEncoder.packFogAndCutout(material);
-		int packedMaterialProperties = MaterialEncoder.packProperties(material);
-		GL32.glUniform4ui(uniformLocation, vertexIndex, fragmentIndex, packedFogAndCutout, packedMaterialProperties);
 	}
 }

src/main/java/com/jozufozu/flywheel/lib/model/LineModelBuilder.java

@@ -98,7 +98,7 @@ public class LineModelBuilder {
 
 	public static class LineMesh implements Mesh {
 		public static final IndexSequence INDEX_SEQUENCE = (ptr, count) -> {
-			int numVertices = 4 * (count / 6);
+			int numVertices = 2 * count / 3;
 			int baseVertex = 0;
 			while (baseVertex < numVertices) {
 				// triangle a