Reduced to ashes

- renderCrumblingInstances accepts a list.
- Implement crumbling for InstancingEngine.
  - It's ugly.
  - Track what draw calls belong with what instancers.
  - DrawCalls lazily create a second VAO for one-off rendering.
  - Bind instance vbo with offset to scratch VAO to emulate a draw with
    baseInstance.
- Ignore discard predicate in crumbling context.
- SimpleContext takes a Consumer to set sampler bindings.
- Fix debugCrumbling command.
- Compile shaders against all contexts.

Side note: not sure if Context is the right place for crumbling. It
feels like it should be a material, but I don't know how that would
work.

src/main/java/com/jozufozu/flywheel/api/backend/Engine.java

@@ -1,5 +1,7 @@
 package com.jozufozu.flywheel.api.backend;
 
+import java.util.List;
+
 import com.jozufozu.flywheel.api.event.RenderContext;
 import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.instance.Instance;
@@ -25,7 +27,14 @@ public interface Engine extends InstancerProvider {
 	 */
 	void renderStage(TaskExecutor executor, RenderContext context, RenderStage stage);
 
-	void renderCrumblingInstance(TaskExecutor taskExecutor, RenderContext context, Instance instance, int progress);
+	/**
+	 * Render the given instances as a crumbling overlay.
+	 * @param taskExecutor The task executor running the frame plan.
+	 * @param context The render context for this frame.
+	 * @param instances The instances to render.
+	 * @param progress The progress of the crumbling animation, i.e. which texture to use.
+	 */
+	void renderCrumblingInstances(TaskExecutor taskExecutor, RenderContext context, List<Instance> instances, int progress);
 
 	/**
 	 * Maintain the render origin to be within a certain distance from the camera in all directions,

src/main/java/com/jozufozu/flywheel/backend/compile/FlwPrograms.java

@@ -2,6 +2,7 @@ package com.jozufozu.flywheel.backend.compile;
 
 import com.google.common.collect.ImmutableList;
 import com.jozufozu.flywheel.Flywheel;
+import com.jozufozu.flywheel.api.context.Context;
 import com.jozufozu.flywheel.api.instance.InstanceType;
 import com.jozufozu.flywheel.api.uniform.ShaderUniforms;
 import com.jozufozu.flywheel.api.vertex.VertexType;
@@ -76,9 +77,12 @@ public class FlwPrograms {
 
 	private static ImmutableList<PipelineProgramKey> createPipelineKeys() {
 		ImmutableList.Builder<PipelineProgramKey> builder = ImmutableList.builder();
-		for (InstanceType<?> instanceType : InstanceType.REGISTRY) {
-			for (VertexType vertexType : VertexType.REGISTRY) {
-				builder.add(new PipelineProgramKey(vertexType, instanceType, Contexts.WORLD));
+		// TODO: ubershader'd contexts?
+		for (Context context : Context.REGISTRY) {
+			for (InstanceType<?> instanceType : InstanceType.REGISTRY) {
+				for (VertexType vertexType : VertexType.REGISTRY) {
+					builder.add(new PipelineProgramKey(vertexType, instanceType, context));
+				}
 			}
 		}
 		return builder.build();

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

@@ -81,7 +81,7 @@ public abstract class AbstractInstancer<I extends Instance> implements Instancer
 				handles.set(j, handle);
 				instances.set(j, instance);
 
-				handle.setIndex(j);
+				handle.index = j;
 				changed.set(j);
 			}
 		}

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

@@ -4,7 +4,7 @@ import com.jozufozu.flywheel.api.instance.InstanceHandle;
 
 public class InstanceHandleImpl implements InstanceHandle {
 	public final AbstractInstancer<?> instancer;
-	private int index;
+	public int index;
 
 	public InstanceHandleImpl(AbstractInstancer<?> instancer, int index) {
 		this.instancer = instancer;
@@ -21,10 +21,6 @@ public class InstanceHandleImpl implements InstanceHandle {
 		instancer.notifyRemoval(index);
 	}
 
-	public void setIndex(int i) {
-		index = i;
-	}
-
 	public void clear() {
 		index = -1;
 	}

src/main/java/com/jozufozu/flywheel/backend/engine/batching/BatchingEngine.java

@@ -94,7 +94,7 @@ public class BatchingEngine extends AbstractEngine implements SimplyComposedPlan
 	}
 
 	@Override
-	public void renderCrumblingInstance(TaskExecutor taskExecutor, RenderContext context, Instance instance, int progress) {
+	public void renderCrumblingInstances(TaskExecutor taskExecutor, RenderContext context, List<Instance> instances, int progress) {
 		// TODO: implement
 	}
 

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

@@ -1,5 +1,7 @@
 package com.jozufozu.flywheel.backend.engine.indirect;
 
+import java.util.List;
+
 import org.lwjgl.opengl.GL32;
 
 import com.jozufozu.flywheel.api.event.RenderContext;
@@ -69,7 +71,7 @@ public class IndirectEngine extends AbstractEngine {
 	}
 
 	@Override
-	public void renderCrumblingInstance(TaskExecutor taskExecutor, RenderContext context, Instance instance, int progress) {
+	public void renderCrumblingInstances(TaskExecutor taskExecutor, RenderContext context, List<Instance> instances, int progress) {
 		// TODO: implement
 	}
 

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

@@ -3,15 +3,18 @@ package com.jozufozu.flywheel.backend.engine.instancing;
 import com.jozufozu.flywheel.gl.array.GlVertexArray;
 
 public class DrawCall {
+	public final ShaderState shaderState;
 	private final InstancedInstancer<?> instancer;
 	private final InstancedMeshPool.BufferedMesh mesh;
 
 	private final int meshAttributes;
 	private GlVertexArray vao;
+	private GlVertexArray vaoScratch;
 
-	public DrawCall(InstancedInstancer<?> instancer, InstancedMeshPool.BufferedMesh mesh) {
+	public DrawCall(InstancedInstancer<?> instancer, InstancedMeshPool.BufferedMesh mesh, ShaderState shaderState) {
 		this.instancer = instancer;
 		this.mesh = mesh;
+		this.shaderState = shaderState;
 
 		meshAttributes = this.mesh.getAttributeCount();
 		vao = GlVertexArray.create();
@@ -22,14 +25,14 @@ public class DrawCall {
 	}
 
 	public void render() {
-		if (isInvalid()) {
+		if (isInvalid() || mesh.isEmpty()) {
 			return;
 		}
 
 		instancer.update();
 
 		int instanceCount = instancer.getInstanceCount();
-		if (instanceCount <= 0 || mesh.isEmpty()) {
+		if (instanceCount <= 0) {
 			return;
 		}
 
@@ -41,12 +44,44 @@ public class DrawCall {
 		mesh.draw(instanceCount);
 	}
 
-	public void delete() {
-		if (vao == null) {
+	public void renderOne(int index) {
+		if (isInvalid() || mesh.isEmpty()) {
 			return;
 		}
 
-		vao.delete();
-		vao = null;
+		instancer.update();
+
+		int instanceCount = instancer.getInstanceCount();
+		if (instanceCount <= 0 || index >= instanceCount) {
+			return;
+		}
+
+		var vao = lazyScratchVao();
+
+		instancer.bindRaw(vao, meshAttributes, index);
+		mesh.setup(vao);
+
+		vao.bindForDraw();
+
+		mesh.draw(1);
 	}
+
+	private GlVertexArray lazyScratchVao() {
+		if (vaoScratch == null) {
+			vaoScratch = GlVertexArray.create();
+		}
+		return vaoScratch;
+	}
+
+	public void delete() {
+        if (vao != null) {
+            vao.delete();
+            vao = null;
+        }
+
+		if (vaoScratch != null) {
+			vaoScratch.delete();
+			vaoScratch = null;
+		}
+    }
 }

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

@@ -25,7 +25,7 @@ import com.jozufozu.flywheel.backend.engine.InstancerKey;
 public class InstancedDrawManager {
 	private final Map<InstancerKey<?>, InstancedInstancer<?>> instancers = new HashMap<>();
 	private final List<UninitializedInstancer> uninitializedInstancers = new ArrayList<>();
-	private final List<InstancedInstancer<?>> initializedInstancers = new ArrayList<>();
+	private final List<InitializedInstancer> initializedInstancers = new ArrayList<>();
 	private final Map<RenderStage, DrawSet> drawSets = new EnumMap<>(RenderStage.class);
 	private final Map<VertexType, InstancedMeshPool> meshPools = new HashMap<>();
 	private final EBOCache eboCache = new EBOCache();
@@ -68,27 +68,33 @@ public class InstancedDrawManager {
 				.forEach(DrawSet::delete);
 		drawSets.clear();
 
-		initializedInstancers.forEach(InstancedInstancer::delete);
+		initializedInstancers.forEach(InitializedInstancer::deleteInstancer);
 		initializedInstancers.clear();
 
 		eboCache.invalidate();
 	}
 
 	public void clearInstancers() {
-		initializedInstancers.forEach(InstancedInstancer::clear);
+		initializedInstancers.forEach(InitializedInstancer::clear);
 	}
 
 	private void add(InstancedInstancer<?> instancer, Model model, RenderStage stage) {
 		instancer.init();
+
 		DrawSet drawSet = drawSets.computeIfAbsent(stage, DrawSet::new);
+		List<DrawCall> drawCalls = new ArrayList<>();
+
 		var meshes = model.getMeshes();
 		for (var entry : meshes.entrySet()) {
 			var mesh = alloc(entry.getValue());
+
 			ShaderState shaderState = new ShaderState(entry.getKey(), mesh.getVertexType(), instancer.type);
-			DrawCall drawCall = new DrawCall(instancer, mesh);
+			DrawCall drawCall = new DrawCall(instancer, mesh, shaderState);
+
 			drawSet.put(shaderState, drawCall);
+			drawCalls.add(drawCall);
 		}
-		initializedInstancers.add(instancer);
+		initializedInstancers.add(new InitializedInstancer(instancer, drawCalls));
 	}
 
 	private InstancedMeshPool.BufferedMesh alloc(Mesh mesh) {
@@ -96,6 +102,16 @@ public class InstancedDrawManager {
 				.alloc(mesh, eboCache);
 	}
 
+	public List<DrawCall> drawCallsForInstancer(InstancedInstancer<?> instancer) {
+		for (InitializedInstancer initializedInstancer : initializedInstancers) {
+			if (initializedInstancer.instancer == instancer) {
+				return initializedInstancer.drawCalls;
+			}
+		}
+
+		return List.of();
+	}
+
 	public static class DrawSet implements Iterable<Map.Entry<ShaderState, Collection<DrawCall>>> {
 		public static final DrawSet EMPTY = new DrawSet(ImmutableListMultimap.of());
 
@@ -134,4 +150,14 @@ public class InstancedDrawManager {
 
 	private record UninitializedInstancer(InstancedInstancer<?> instancer, Model model, RenderStage stage) {
 	}
+
+	private record InitializedInstancer(InstancedInstancer<?> instancer, List<DrawCall> drawCalls) {
+		public void deleteInstancer() {
+			instancer.delete();
+		}
+
+		public void clear() {
+			instancer.clear();
+		}
+	}
 }

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

@@ -84,7 +84,12 @@ public class InstancedInstancer<I extends Instance> extends AbstractInstancer<I>
 			return;
 		}
 
-		vao.bindVertexBuffer(1, vbo.handle(), 0L, instanceStride);
+		bindRaw(vao, startAttrib, 0);
+	}
+
+	public void bindRaw(GlVertexArray vao, int startAttrib, int baseInstance) {
+		long offset = (long) baseInstance * instanceStride;
+		vao.bindVertexBuffer(1, vbo.handle(), offset, instanceStride);
 		vao.setBindingDivisor(1, 1);
 		vao.bindAttributes(1, startAttrib, instanceFormat.attributes());
 	}

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

@@ -1,5 +1,7 @@
 package com.jozufozu.flywheel.backend.engine.instancing;
 
+import java.util.List;
+
 import org.lwjgl.opengl.GL32;
 
 import com.jozufozu.flywheel.api.context.Context;
@@ -13,9 +15,12 @@ import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
 import com.jozufozu.flywheel.backend.compile.InstancingPrograms;
 import com.jozufozu.flywheel.backend.engine.AbstractEngine;
+import com.jozufozu.flywheel.backend.engine.InstanceHandleImpl;
 import com.jozufozu.flywheel.backend.engine.UniformBuffer;
+import com.jozufozu.flywheel.backend.engine.indirect.Textures;
 import com.jozufozu.flywheel.gl.GlStateTracker;
 import com.jozufozu.flywheel.gl.GlTextureUnit;
+import com.jozufozu.flywheel.lib.context.Contexts;
 import com.jozufozu.flywheel.lib.material.MaterialIndices;
 import com.jozufozu.flywheel.lib.task.Flag;
 import com.jozufozu.flywheel.lib.task.NamedFlag;
@@ -24,6 +29,8 @@ import com.jozufozu.flywheel.lib.task.SyncedPlan;
 import com.mojang.blaze3d.systems.RenderSystem;
 
 import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.RenderType;
+import net.minecraft.client.resources.model.ModelBakery;
 
 public class InstancingEngine extends AbstractEngine {
 	private final Context context;
@@ -76,8 +83,39 @@ public class InstancingEngine extends AbstractEngine {
 	}
 
 	@Override
-	public void renderCrumblingInstance(TaskExecutor taskExecutor, RenderContext context, Instance instance, int progress) {
-		// TODO: implement
+	public void renderCrumblingInstances(TaskExecutor taskExecutor, RenderContext context, List<Instance> instances, int progress) {
+		// TODO: optimize
+
+		taskExecutor.syncUntil(flushFlag::isRaised);
+
+		var type = ModelBakery.DESTROY_TYPES.get(progress);
+
+		try (var state = GlStateTracker.getRestoreState()) {
+			type.setupRenderState();
+
+			Textures.bindActiveTextures();
+
+			for (Instance instance : instances) {
+				if (!(instance.handle() instanceof InstanceHandleImpl impl)) {
+					continue;
+				}
+				if (!(impl.instancer instanceof InstancedInstancer<?> instancer)) {
+					continue;
+				}
+
+				List<DrawCall> draws = drawManager.drawCallsForInstancer(instancer);
+
+				draws.removeIf(DrawCall::isInvalid);
+
+				for (DrawCall draw : draws) {
+					var shader = draw.shaderState;
+
+					setup(shader, Contexts.CRUMBLING);
+
+					draw.renderOne(impl.index);
+				}
+			}
+		}
 	}
 
 	private void setup() {

src/main/java/com/jozufozu/flywheel/config/FlwCommands.java

@@ -116,7 +116,7 @@ public class FlwCommands {
 				.then(Commands.argument("pos", BlockPosArgument.blockPos())
 						.then(Commands.argument("stage", IntegerArgumentType.integer(0, 9))
 								.executes(context -> {
-									BlockPos pos = BlockPosArgument.getLoadedBlockPos(context, "pos");
+									BlockPos pos = BlockPosArgument.getBlockPos(context, "pos");
 									int value = IntegerArgumentType.getInteger(context, "stage");
 
 									Entity executor = context.getSource()
@@ -145,6 +145,7 @@ public class FlwCommands {
 						}))
 				.then(Commands.literal("capture")
 						.executes(context -> {
+							FlwShaderUniforms.FRUSTUM_PAUSED = true;
 							FlwShaderUniforms.FRUSTUM_CAPTURE = true;
 							return 1;
 						})));

src/main/java/com/jozufozu/flywheel/impl/visualization/VisualizationManagerImpl.java

@@ -8,7 +8,6 @@ import com.jozufozu.flywheel.api.backend.BackendManager;
 import com.jozufozu.flywheel.api.backend.Engine;
 import com.jozufozu.flywheel.api.event.RenderContext;
 import com.jozufozu.flywheel.api.event.RenderStage;
-import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
 import com.jozufozu.flywheel.api.visual.DynamicVisual;
@@ -220,9 +219,9 @@ public class VisualizationManagerImpl implements VisualizationManager {
 				continue;
 			}
 
-			var instanceList = visual.getCrumblingInstances();
+			var instances = visual.getCrumblingInstances();
 
-			if (instanceList.isEmpty()) {
+			if (instances.isEmpty()) {
 				// The visual doesn't want to render anything crumbling.
 				continue;
 			}
@@ -232,9 +231,7 @@ public class VisualizationManagerImpl implements VisualizationManager {
 			int progress = set.last()
 					.getProgress();
 
-			for (Instance instance : instanceList) {
-				engine.renderCrumblingInstance(taskExecutor, context, instance, progress);
-			}
+			engine.renderCrumblingInstances(taskExecutor, context, instances, progress);
         }
 	}
 

src/main/java/com/jozufozu/flywheel/lib/context/Contexts.java

@@ -4,13 +4,26 @@ import org.jetbrains.annotations.ApiStatus;
 
 import com.jozufozu.flywheel.Flywheel;
 import com.jozufozu.flywheel.api.context.Context;
+import com.jozufozu.flywheel.gl.shader.GlProgram;
 import com.jozufozu.flywheel.lib.util.ResourceUtil;
 
 import net.minecraft.resources.ResourceLocation;
 
 public final class Contexts {
-	public static final SimpleContext WORLD = Context.REGISTRY.registerAndGet(new SimpleContext(Files.WORLD_VERTEX, Files.WORLD_FRAGMENT));
-	public static final SimpleContext CRUMBLING = Context.REGISTRY.registerAndGet(new SimpleContext(Files.WORLD_VERTEX, Files.CRUMBLING_FRAGMENT));
+	public static final SimpleContext WORLD = Context.REGISTRY.registerAndGet(new SimpleContext(Files.WORLD_VERTEX, Files.WORLD_FRAGMENT, program -> {
+		program.bind();
+		program.setSamplerBinding("flw_diffuseTex", 0);
+		program.setSamplerBinding("flw_overlayTex", 1);
+		program.setSamplerBinding("flw_lightTex", 2);
+		GlProgram.unbind();
+	}));
+
+	// TODO: can we make crumbling a fragment material?
+	public static final SimpleContext CRUMBLING = Context.REGISTRY.registerAndGet(new SimpleContext(Files.WORLD_VERTEX, Files.CRUMBLING_FRAGMENT, program -> {
+		program.bind();
+		program.setSamplerBinding("flw_diffuseTex", 0);
+		GlProgram.unbind();
+	}));
 
 	private Contexts() {
 	}

src/main/java/com/jozufozu/flywheel/lib/context/SimpleContext.java

@@ -1,18 +1,16 @@
 package com.jozufozu.flywheel.lib.context;
 
+import java.util.function.Consumer;
+
 import com.jozufozu.flywheel.api.context.Context;
 import com.jozufozu.flywheel.gl.shader.GlProgram;
 
 import net.minecraft.resources.ResourceLocation;
 
-public record SimpleContext(ResourceLocation vertexShader, ResourceLocation fragmentShader) implements Context {
+public record SimpleContext(ResourceLocation vertexShader, ResourceLocation fragmentShader, Consumer<GlProgram> onLink) implements Context {
 	@Override
 	public void onProgramLink(GlProgram program) {
-		program.bind();
-		program.setSamplerBinding("flw_diffuseTex", 0);
-		program.setSamplerBinding("flw_overlayTex", 1);
-		program.setSamplerBinding("flw_lightTex", 2);
-		GlProgram.unbind();
+		onLink.accept(program);
 	}
 
 	@Override

src/main/resources/assets/flywheel/flywheel/context/crumbling.frag

@@ -34,7 +34,8 @@ void flw_initFragment() {
 void flw_contextFragment() {
     vec4 color = flw_fragColor;
 
-    if (flw_discardPredicate(color)) {
+    // Ignore the discard predicate since we control the texture.
+    if (color.a < 0.01) {
         discard;
     }