Debugging broken overlay/lighting

- Break instance overlay/light back into 2 layout elements
- Write light directly as an int
- Make light a short backed float element
- Clamp overlay coords in common.frag to avoid explosions
- Explosions: integer vertex attributes sometimes blow up to massive
  sizes, greater than Short.MAX_VALUE which should not be possible.
- Reorganize some texture/uniform binding code

src/main/java/com/jozufozu/flywheel/backend/InternalVertex.java

@@ -4,9 +4,9 @@ import java.util.List;
 
 import com.jozufozu.flywheel.Flywheel;
 import com.jozufozu.flywheel.api.layout.FloatRepr;
+import com.jozufozu.flywheel.api.layout.IntegerRepr;
 import com.jozufozu.flywheel.api.layout.Layout;
 import com.jozufozu.flywheel.api.layout.LayoutBuilder;
-import com.jozufozu.flywheel.api.layout.UnsignedIntegerRepr;
 import com.jozufozu.flywheel.api.vertex.VertexView;
 import com.jozufozu.flywheel.backend.engine.LayoutAttributes;
 import com.jozufozu.flywheel.backend.gl.array.VertexAttribute;
@@ -19,7 +19,7 @@ public final class InternalVertex {
 			.vector("position", FloatRepr.FLOAT, 3)
 			.vector("color", FloatRepr.NORMALIZED_UNSIGNED_BYTE, 4)
 			.vector("tex", FloatRepr.FLOAT, 2)
-			.vector("overlay_light", UnsignedIntegerRepr.UNSIGNED_SHORT, 4)
+			.vector("overlay_light", IntegerRepr.SHORT, 4)
 			.vector("normal", FloatRepr.NORMALIZED_BYTE, 3)
 			.build();
 

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

@@ -0,0 +1,89 @@
+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;
+
+import it.unimi.dsi.fastutil.objects.Reference2IntMap;
+import it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap;
+
+public class IndexPool {
+	private final GlBuffer ebo;
+
+	private final Reference2IntMap<IndexSequence> indexCounts;
+	private final Reference2IntMap<IndexSequence> firstIndices;
+
+	private boolean dirty;
+
+    public IndexPool() {
+        ebo = new GlBuffer();
+
+		indexCounts = new Reference2IntOpenHashMap<>();
+		firstIndices = new Reference2IntOpenHashMap<>();
+
+		indexCounts.defaultReturnValue(0);
+	}
+
+	public int firstIndex(IndexSequence sequence) {
+		return firstIndices.getInt(sequence);
+	}
+
+	public void reset() {
+		indexCounts.clear();
+		firstIndices.clear();
+		dirty = true;
+	}
+
+	public void updateCount(IndexSequence sequence, int indexCount) {
+		int oldCount = indexCounts.getInt(sequence);
+		int newCount = Math.max(oldCount, indexCount);
+
+		if (newCount > oldCount) {
+			indexCounts.put(sequence, newCount);
+			dirty = true;
+		}
+	}
+
+	public void flush() {
+		if (!dirty) {
+			return;
+		}
+
+		firstIndices.clear();
+		dirty = false;
+
+		long totalIndexCount = 0;
+
+		for (int count : indexCounts.values()) {
+			totalIndexCount += count;
+		}
+
+		final var indexBlock = MemoryBlock.malloc(totalIndexCount * GlNumericType.UINT.byteWidth());
+		final long indexPtr = indexBlock.ptr();
+
+		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;
+		}
+
+		ebo.upload(indexBlock);
+		indexBlock.free();
+	}
+
+	public void bind(GlVertexArray vertexArray) {
+		vertexArray.setElementBuffer(ebo.handle());
+	}
+
+	public void delete() {
+		ebo.delete();
+	}
+}

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

@@ -9,27 +9,24 @@ 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 List<BufferedMesh> recentlyAllocated = new ArrayList<>();
 
 	private final GlBuffer vbo;
-	private final GlBuffer ebo;
+	private final IndexPool indexPool;
 
 	private boolean dirty;
 	private boolean anyToRemove;
@@ -40,7 +37,7 @@ public class MeshPool {
 	public MeshPool() {
 		vertexView = InternalVertex.createVertexView();
 		vbo = new GlBuffer();
-		ebo = new GlBuffer();
+		indexPool = new IndexPool();
 	}
 
 	/**
@@ -56,6 +53,7 @@ public class MeshPool {
 	private BufferedMesh _alloc(Mesh m) {
 		BufferedMesh bufferedModel = new BufferedMesh(m);
 		meshList.add(bufferedModel);
+		recentlyAllocated.add(bufferedModel);
 
 		dirty = true;
 		return bufferedModel;
@@ -74,9 +72,23 @@ public class MeshPool {
 		if (anyToRemove) {
 			anyToRemove = false;
 			processDeletions();
+
+			// Might want to shrink the index pool if something was removed.
+			indexPool.reset();
+			for (BufferedMesh mesh : meshList) {
+				indexPool.updateCount(mesh.mesh.indexSequence(), mesh.indexCount());
+			}
+		} else {
+			// Otherwise, just update the index with the new counts.
+			for (BufferedMesh mesh : recentlyAllocated) {
+				indexPool.updateCount(mesh.mesh.indexSequence(), mesh.indexCount());
+			}
 		}
 
-        uploadAll();
+		// Always need to flush the index pool.
+		indexPool.flush();
+
+		uploadAll();
         dirty = false;
     }
 
@@ -93,41 +105,8 @@ public class MeshPool {
 
 	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);
@@ -144,25 +123,25 @@ public class MeshPool {
 			byteIndex += mesh.byteSize();
 			baseVertex += mesh.vertexCount();
 
-			mesh.firstIndex = firstIndices.getInt(mesh.mesh.indexSequence());
+			mesh.firstIndex = indexPool.firstIndex(mesh.mesh.indexSequence());
+
+			mesh.boundTo.clear();
 		}
 
 		vbo.upload(vertexBlock);
-		ebo.upload(indexBlock);
 
 		vertexBlock.free();
-		indexBlock.free();
 	}
 
 	public void bind(GlVertexArray vertexArray) {
-		vertexArray.setElementBuffer(ebo.handle());
+		indexPool.bind(vertexArray);
 		vertexArray.bindVertexBuffer(0, vbo.handle(), 0, InternalVertex.STRIDE);
 		vertexArray.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
 	}
 
 	public void delete() {
 		vbo.delete();
-		ebo.delete();
+		indexPool.delete();
 		meshes.clear();
 		meshList.clear();
 	}
@@ -228,12 +207,13 @@ public class MeshPool {
 		}
 
 		public void setup(GlVertexArray vao) {
-			if (boundTo.add(vao)) {
+            if (!boundTo.add(vao)) {
-				vao.setElementBuffer(MeshPool.this.ebo.handle());
+                return;
-				vao.bindVertexBuffer(0, MeshPool.this.vbo.handle(), byteIndex, InternalVertex.STRIDE);
+            }
-				vao.bindAttributes(0, 0, InternalVertex.ATTRIBUTES);
+            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++;

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

@@ -7,7 +7,6 @@ import java.util.Set;
 
 import org.jetbrains.annotations.Nullable;
 
-import com.jozufozu.flywheel.Flywheel;
 import com.jozufozu.flywheel.api.context.Context;
 import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.api.instance.InstanceType;
@@ -18,7 +17,7 @@ import com.jozufozu.flywheel.backend.gl.array.GlVertexArray;
 import com.jozufozu.flywheel.backend.gl.array.VertexAttribute;
 import com.jozufozu.flywheel.backend.gl.buffer.GlBuffer;
 import com.jozufozu.flywheel.backend.gl.buffer.GlBufferUsage;
-import com.jozufozu.flywheel.backend.gl.buffer.MappedBuffer;
+import com.jozufozu.flywheel.lib.memory.MemoryBlock;
 
 public class InstancedInstancer<I extends Instance> extends AbstractInstancer<I> {
 	private final List<VertexAttribute> instanceAttributes;
@@ -45,7 +44,6 @@ public class InstancedInstancer<I extends Instance> extends AbstractInstancer<I>
 		}
 
 		vbo = new GlBuffer(GlBufferUsage.DYNAMIC_DRAW);
-		vbo.growthFunction(l -> Math.max(l + (long) instanceStride * 16, (long) (l * 1.6)));
 	}
 
 	public void update() {
@@ -59,28 +57,61 @@ public class InstancedInstancer<I extends Instance> extends AbstractInstancer<I>
 		}
 
 		int byteSize = instanceStride * instances.size();
-		if (vbo.ensureCapacity(byteSize)) {
+		if (needsToGrow(byteSize)) {
-			// The vbo has moved, so we need to re-bind attributes
+			// TODO: Should this memory block be persistent?
-			boundTo.clear();
+			var temp = MemoryBlock.malloc(increaseSize(byteSize));
+
+			writeAll(temp.ptr());
+
+			vbo.upload(temp);
+
+			temp.free();
+		} else {
+			writeChanged();
 		}
 
-		try (MappedBuffer buf = vbo.map()) {
+		changed.clear();
-            writeChanged(buf.ptr());
-
-			changed.clear();
-		} catch (Exception e) {
-			Flywheel.LOGGER.error("Error updating InstancedInstancer:", e);
-		}
 	}
 
-	private void writeChanged(long ptr) {
+	private void writeChanged() {
 		changed.forEachSetSpan((startInclusive, endInclusive) -> {
+			var temp = MemoryBlock.malloc((long) instanceStride * (endInclusive - startInclusive + 1));
+			long ptr = temp.ptr();
 			for (int i = startInclusive; i <= endInclusive; i++) {
-				writer.write(ptr + (long) instanceStride * i, instances.get(i));
+				writer.write(ptr, instances.get(i));
+				ptr += instanceStride;
 			}
+
+			vbo.uploadSpan((long) startInclusive * instanceStride, temp);
+
+			temp.free();
 		});
 	}
 
+	private void writeAll(long ptr) {
+		for (I instance : instances) {
+			writer.write(ptr, instance);
+			ptr += instanceStride;
+		}
+	}
+
+	private long increaseSize(long capacity) {
+		return Math.max(capacity + (long) instanceStride * 16, (long) (capacity * 1.6));
+	}
+
+	public boolean needsToGrow(long capacity) {
+		if (capacity < 0) {
+			throw new IllegalArgumentException("Size " + capacity + " < 0");
+		}
+
+		if (capacity == 0) {
+			return false;
+		}
+
+        return capacity > vbo.size();
+    }
+
+
 	/**
 	 * Bind this instancer's vbo to the given vao if it hasn't already been bound.
 	 * @param vao The vao to bind to.

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

@@ -64,6 +64,7 @@ public class InstancingEngine extends AbstractEngine {
 		}
 
 		try (var state = GlStateTracker.getRestoreState()) {
+			Uniforms.bindForDraw();
 			render(drawSet);
 		}
 	}
@@ -104,7 +105,6 @@ public class InstancingEngine extends AbstractEngine {
 			var program = programs.get(shader.instanceType(), context.contextShader());
 			program.bind();
 
-			Uniforms.bindForDraw();
 			uploadMaterialUniform(program, material);
 
 			context.prepare(material, program, textures);

src/main/java/com/jozufozu/flywheel/backend/engine/textures/TextureBinder.java

@@ -48,14 +48,15 @@ public class TextureBinder {
 
 	public static void bindLightAndOverlay() {
 		var gameRenderer = Minecraft.getInstance().gameRenderer;
-		gameRenderer.overlayTexture()
-				.setupOverlayColor();
-		gameRenderer.lightTexture()
-				.turnOnLightLayer();
 
 		GlTextureUnit.T1.makeActive();
+		gameRenderer.overlayTexture()
+				.setupOverlayColor();
 		RenderSystem.bindTexture(RenderSystem.getShaderTexture(1));
+
 		GlTextureUnit.T2.makeActive();
+		gameRenderer.lightTexture()
+				.turnOnLightLayer();
 		RenderSystem.bindTexture(RenderSystem.getShaderTexture(2));
 	}
 

src/main/java/com/jozufozu/flywheel/backend/engine/uniform/FrameUniforms.java

@@ -15,8 +15,10 @@ import net.minecraft.world.phys.Vec3;
 
 public class FrameUniforms implements UniformProvider {
 	public static final int SIZE = 304;
+	public int debugMode;
+	public int debugOverlay;
 
-	@Nullable
+    @Nullable
 	private RenderContext context;
 
 	private final Matrix4f viewProjection = new Matrix4f();
@@ -70,7 +72,10 @@ public class FrameUniforms implements UniformProvider {
 		MemoryUtil.memPutInt(ptr, getConstantAmbientLightFlag(context));
 		ptr += 4;
 
-		writeTime(ptr);
+		ptr = writeTime(ptr);
+
+		MemoryUtil.memPutInt(ptr, debugMode);
+		MemoryUtil.memPutInt(ptr + 4, debugOverlay);
 	}
 
 	private long writeMatrices(long ptr) {

src/main/java/com/jozufozu/flywheel/backend/engine/uniform/Uniforms.java

@@ -3,6 +3,8 @@ package com.jozufozu.flywheel.backend.engine.uniform;
 import com.jozufozu.flywheel.api.event.ReloadLevelRendererEvent;
 import com.jozufozu.flywheel.api.event.RenderContext;
 import com.jozufozu.flywheel.backend.gl.GlStateTracker;
+import com.jozufozu.flywheel.config.DebugMode;
+import com.jozufozu.flywheel.config.DebugOverlay;
 
 public class Uniforms {
 	public static boolean frustumPaused = false;
@@ -53,6 +55,11 @@ public class Uniforms {
 		ubo.update();
 	}
 
+	public static void setDebugMode(DebugMode mode, DebugOverlay visual) {
+		frame().provider.debugMode = mode.ordinal();
+		frame().provider.debugOverlay = visual.ordinal();
+	}
+
 	public static void onReloadLevelRenderer(ReloadLevelRendererEvent event) {
 		if (frame != null) {
 			frame.delete();

src/main/java/com/jozufozu/flywheel/backend/gl/buffer/Buffer.java

@@ -1,8 +1,6 @@
 package com.jozufozu.flywheel.backend.gl.buffer;
 
 import org.lwjgl.opengl.GL15;
-import org.lwjgl.opengl.GL30;
-import org.lwjgl.opengl.GL31;
 import org.lwjgl.opengl.GL45C;
 import org.lwjgl.system.Checks;
 
@@ -15,11 +13,7 @@ public interface Buffer {
 
 	void data(int vbo, long size, long ptr, int glEnum);
 
-	void copyData(int src, int dst, long srcOffset, long dstOffset, long size);
+	void subData(int vbo, long offset, long size, long ptr);
-
-	long mapRange(int handle, int offset, long size, int access);
-
-	void unmap(int handle);
 
 	class DSA implements Buffer {
 		@Override
@@ -33,18 +27,8 @@ public interface Buffer {
 		}
 
 		@Override
-		public void copyData(int src, int dst, long srcOffset, long dstOffset, long size) {
+		public void subData(int vbo, long offset, long size, long ptr) {
-			GL45C.glCopyNamedBufferSubData(src, dst, srcOffset, dstOffset, size);
+			GL45C.nglNamedBufferSubData(vbo, offset, size, ptr);
-		}
-
-		@Override
-		public long mapRange(int handle, int offset, long size, int access) {
-			return GL45C.nglMapNamedBufferRange(handle, offset, size, access);
-		}
-
-		@Override
-		public void unmap(int handle) {
-			GL45C.glUnmapNamedBuffer(handle);
 		}
 
 		public Buffer fallback() {
@@ -73,23 +57,9 @@ public interface Buffer {
 		}
 
 		@Override
-		public void copyData(int src, int dst, long size, long srcOffset, long dstOffset) {
+		public void subData(int vbo, long offset, long size, long ptr) {
-			GlBufferType.COPY_READ_BUFFER.bind(src);
+			GlBufferType.COPY_WRITE_BUFFER.bind(vbo);
-			GlBufferType.COPY_WRITE_BUFFER.bind(dst);
+			GL15.nglBufferSubData(GlBufferType.COPY_WRITE_BUFFER.glEnum, offset, size, ptr);
-
-			GL31.glCopyBufferSubData(GlBufferType.COPY_READ_BUFFER.glEnum, GlBufferType.COPY_WRITE_BUFFER.glEnum, srcOffset, dstOffset, size);
-		}
-
-		@Override
-		public long mapRange(int handle, int offset, long size, int access) {
-			GlBufferType.COPY_READ_BUFFER.bind(handle);
-			return GL30.nglMapBufferRange(GlBufferType.COPY_READ_BUFFER.glEnum, 0, size, access);
-		}
-
-		@Override
-		public void unmap(int handle) {
-			GlBufferType.COPY_READ_BUFFER.bind(handle);
-			GL15.glUnmapBuffer(GlBufferType.COPY_READ_BUFFER.glEnum);
 		}
 	}
 }

src/main/java/com/jozufozu/flywheel/backend/gl/buffer/GlBuffer.java

@@ -1,24 +1,16 @@
 package com.jozufozu.flywheel.backend.gl.buffer;
 
-import org.lwjgl.system.MemoryUtil;
-
 import com.jozufozu.flywheel.backend.gl.GlObject;
 import com.jozufozu.flywheel.lib.memory.FlwMemoryTracker;
 import com.jozufozu.flywheel.lib.memory.MemoryBlock;
 import com.mojang.blaze3d.platform.GlStateManager;
 
-import it.unimi.dsi.fastutil.longs.LongUnaryOperator;
-
 public class GlBuffer extends GlObject {
 	protected final GlBufferUsage usage;
 	/**
 	 * The size (in bytes) of the buffer on the GPU.
 	 */
 	protected long size;
-	/**
-	 * A mapping to adjust the size of the buffer when allocating.
-	 */
-	protected LongUnaryOperator growthFunction = LongUnaryOperator.identity();
 
 	public GlBuffer() {
 		this(GlBufferUsage.STATIC_DRAW);
@@ -29,63 +21,9 @@ public class GlBuffer extends GlObject {
 		this.usage = usage;
 	}
 
-	/**
-	 * @return true if the buffer was recreated.
-	 */
-	public boolean ensureCapacity(long capacity) {
-		if (capacity < 0) {
-			throw new IllegalArgumentException("Size " + capacity + " < 0");
-		}
-
-		if (capacity == 0) {
-			return false;
-		}
-
-		if (size == 0) {
-			alloc(capacity);
-			return true;
-		}
-
-		if (capacity > size) {
-			realloc(capacity);
-			return true;
-		}
-
-		return false;
-	}
-
-	private void alloc(long capacity) {
-		increaseSize(capacity);
-		Buffer.IMPL.data(handle(), size, MemoryUtil.NULL, usage.glEnum);
-		FlwMemoryTracker._allocGPUMemory(size);
-	}
-
-	private void realloc(long capacity) {
-		FlwMemoryTracker._freeGPUMemory(size);
-		var oldSize = size;
-		increaseSize(capacity);
-
-		int oldHandle = handle();
-		int newHandle = Buffer.IMPL.create();
-		Buffer.IMPL.data(newHandle, size, MemoryUtil.NULL, usage.glEnum);
-		Buffer.IMPL.copyData(oldHandle, newHandle, 0, 0, oldSize);
-		GlStateManager._glDeleteBuffers(oldHandle);
-		handle(newHandle);
-
-		FlwMemoryTracker._allocGPUMemory(size);
-	}
-
-	/**
-	 * Increase the size of the buffer to at least the given capacity.
-	 */
-	private void increaseSize(long capacity) {
-		size = growthFunction.apply(capacity);
-	}
-
 	public void upload(MemoryBlock memoryBlock) {
 		upload(memoryBlock.ptr(), memoryBlock.size());
 	}
-
 	public void upload(long ptr, long size) {
 		FlwMemoryTracker._freeGPUMemory(this.size);
 		Buffer.IMPL.data(handle(), size, ptr, usage.glEnum);
@@ -93,12 +31,12 @@ public class GlBuffer extends GlObject {
 		FlwMemoryTracker._allocGPUMemory(this.size);
 	}
 
-	public MappedBuffer map() {
+	public void uploadSpan(long offset, MemoryBlock memoryBlock) {
-		return new MappedBuffer(handle(), size);
+		uploadSpan(offset, memoryBlock.ptr(), memoryBlock.size());
 	}
 
-	public void growthFunction(LongUnaryOperator growthFunction) {
+	public void uploadSpan(long offset, long ptr, long size) {
-		this.growthFunction = growthFunction;
+		Buffer.IMPL.subData(handle(), offset, size, ptr);
 	}
 
 	public long size() {

src/main/java/com/jozufozu/flywheel/backend/gl/buffer/MappedBuffer.java

@@ -1,38 +0,0 @@
-package com.jozufozu.flywheel.backend.gl.buffer;
-
-import static org.lwjgl.opengl.GL30.GL_MAP_WRITE_BIT;
-import static org.lwjgl.system.MemoryUtil.NULL;
-
-import org.lwjgl.system.MemoryUtil;
-
-import com.jozufozu.flywheel.backend.gl.error.GlError;
-import com.jozufozu.flywheel.backend.gl.error.GlException;
-
-public class MappedBuffer implements AutoCloseable {
-	private final int glBuffer;
-	private long ptr;
-
-	public MappedBuffer(int glBuffer, long size) {
-		this.glBuffer = glBuffer;
-
-		ptr = Buffer.IMPL.mapRange(glBuffer, 0, size, GL_MAP_WRITE_BIT);
-
-		if (ptr == MemoryUtil.NULL) {
-			throw new GlException(GlError.poll(), "Could not map buffer");
-		}
-	}
-
-	public long ptr() {
-		return ptr;
-	}
-
-	@Override
-	public void close() {
-		if (ptr == NULL) {
-			return;
-		}
-
-		Buffer.IMPL.unmap(glBuffer);
-		ptr = NULL;
-	}
-}

src/main/java/com/jozufozu/flywheel/backend/gl/buffer/MappedBufferUsage.java

@@ -1,16 +0,0 @@
-package com.jozufozu.flywheel.backend.gl.buffer;
-
-import org.lwjgl.opengl.GL15C;
-
-public enum MappedBufferUsage {
-	READ_ONLY(GL15C.GL_READ_ONLY),
-	WRITE_ONLY(GL15C.GL_WRITE_ONLY),
-	READ_WRITE(GL15C.GL_READ_WRITE),
-	;
-
-	int glEnum;
-
-	MappedBufferUsage(int glEnum) {
-		this.glEnum = glEnum;
-	}
-}

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

@@ -0,0 +1,8 @@
+package com.jozufozu.flywheel.config;
+
+public enum DebugMode {
+	NONE,
+	NORMALS,
+	INSTANCE_ID,
+	LIGHT,
+}

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

@@ -0,0 +1,7 @@
+package com.jozufozu.flywheel.config;
+
+public enum DebugOverlay {
+	NONE,
+	MUL,
+	OVERRIDE,
+}

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

@@ -23,6 +23,7 @@ import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.entity.Entity;
 import net.minecraftforge.client.event.RegisterClientCommandsEvent;
 import net.minecraftforge.common.ForgeConfigSpec.ConfigValue;
+import net.minecraftforge.server.command.EnumArgument;
 
 public class FlwCommands {
 	public static void registerClientCommands(RegisterClientCommandsEvent event) {
@@ -101,18 +102,32 @@ public class FlwCommands {
 				}
 			));
 
-		// TODO
+		command.then(Commands.literal("debug")
-		command.then(Commands.literal("debugNormals"))
+				.then(Commands.argument("mode", EnumArgument.enumArgument(DebugMode.class))
-				.executes(context -> {
+						.executes(context -> {
-					LocalPlayer player = Minecraft.getInstance().player;
+							LocalPlayer player = Minecraft.getInstance().player;
-					if (player == null) return 0;
+							if (player == null) return 0;
 
-					player.displayClientMessage(Component.literal("This command is not yet implemented."), false);
+							DebugMode mode = context.getArgument("mode", DebugMode.class);
 
-					return Command.SINGLE_SUCCESS;
+							Uniforms.setDebugMode(mode, DebugOverlay.OVERRIDE);
-				});
 
-		command.then(Commands.literal("debugCrumbling")
+							return Command.SINGLE_SUCCESS;
+						})
+						.then(Commands.argument("overlay", EnumArgument.enumArgument(DebugOverlay.class))
+								.executes(context -> {
+									LocalPlayer player = Minecraft.getInstance().player;
+									if (player == null) return 0;
+
+									DebugMode mode = context.getArgument("mode", DebugMode.class);
+									DebugOverlay visual = context.getArgument("overlay", DebugOverlay.class);
+
+									Uniforms.setDebugMode(mode, visual);
+
+									return Command.SINGLE_SUCCESS;
+								}))));
+
+		command.then(Commands.literal("crumbling")
 				.then(Commands.argument("pos", BlockPosArgument.blockPos())
 						.then(Commands.argument("stage", IntegerArgumentType.integer(0, 9))
 								.executes(context -> {
@@ -132,12 +147,7 @@ public class FlwCommands {
 									return Command.SINGLE_SUCCESS;
 								}))));
 
-		command.then(Commands.literal("debugFrustum")
+		command.then(Commands.literal("frustum")
-				.then(Commands.literal("pause")
-						.executes(context -> {
-							Uniforms.frustumPaused = true;
-							return 1;
-						}))
 				.then(Commands.literal("unpause")
 						.executes(context -> {
 							Uniforms.frustumPaused = false;

src/main/java/com/jozufozu/flywheel/lib/instance/InstanceTypes.java

@@ -14,7 +14,8 @@ public final class InstanceTypes {
 	public static final InstanceType<TransformedInstance> TRANSFORMED = SimpleInstanceType.builder(TransformedInstance::new)
 			.layout(LayoutBuilder.create()
 					.vector("color", FloatRepr.NORMALIZED_UNSIGNED_BYTE, 4)
-					.vector("overlay_light", IntegerRepr.SHORT, 4)
+					.vector("overlay", IntegerRepr.SHORT, 2)
+					.vector("light", FloatRepr.UNSIGNED_SHORT, 2)
 					.matrix("pose", FloatRepr.FLOAT, 4)
 					.matrix("normal", FloatRepr.FLOAT, 3)
 					.build())
@@ -24,8 +25,7 @@ public final class InstanceTypes {
 				MemoryUtil.memPutByte(ptr + 2, instance.b);
 				MemoryUtil.memPutByte(ptr + 3, instance.a);
 				MemoryUtil.memPutInt(ptr + 4, instance.overlay);
-				MemoryUtil.memPutShort(ptr + 8, instance.blockLight);
+				MemoryUtil.memPutInt(ptr + 8, (int) instance.blockLight | (int) instance.skyLight << 16);
-				MemoryUtil.memPutShort(ptr + 10, instance.skyLight);
 				MatrixMath.writeUnsafe(instance.model, ptr + 12);
 				MatrixMath.writeUnsafe(instance.normal, ptr + 76);
 			})
@@ -36,7 +36,8 @@ public final class InstanceTypes {
 	public static final InstanceType<OrientedInstance> ORIENTED = SimpleInstanceType.builder(OrientedInstance::new)
 			.layout(LayoutBuilder.create()
 					.vector("color", FloatRepr.NORMALIZED_UNSIGNED_BYTE, 4)
-					.vector("overlay_light", IntegerRepr.SHORT, 4)
+					.vector("overlay", IntegerRepr.SHORT, 2)
+					.vector("light", FloatRepr.UNSIGNED_SHORT, 2)
 					.vector("position", FloatRepr.FLOAT, 3)
 					.vector("pivot", FloatRepr.FLOAT, 3)
 					.vector("rotation", FloatRepr.FLOAT, 4)
@@ -47,8 +48,7 @@ public final class InstanceTypes {
 				MemoryUtil.memPutByte(ptr + 2, instance.b);
 				MemoryUtil.memPutByte(ptr + 3, instance.a);
 				MemoryUtil.memPutInt(ptr + 4, instance.overlay);
-				MemoryUtil.memPutShort(ptr + 8, instance.blockLight);
+				MemoryUtil.memPutInt(ptr + 8, (int) instance.blockLight | (int) instance.skyLight << 16);
-				MemoryUtil.memPutShort(ptr + 10, instance.skyLight);
 				MemoryUtil.memPutFloat(ptr + 12, instance.posX);
 				MemoryUtil.memPutFloat(ptr + 16, instance.posY);
 				MemoryUtil.memPutFloat(ptr + 20, instance.posZ);

src/main/resources/assets/flywheel/flywheel/instance/oriented.vert

@@ -4,6 +4,6 @@ void flw_instanceVertex(in FlwInstance i) {
     flw_vertexPos = vec4(rotateByQuaternion(flw_vertexPos.xyz - i.pivot, i.rotation) + i.pivot + i.position, 1.0);
     flw_vertexNormal = rotateByQuaternion(flw_vertexNormal, i.rotation);
     flw_vertexColor = i.color;
-    flw_vertexOverlay = i.overlay_light.xy;
+    flw_vertexOverlay = i.overlay;
-    flw_vertexLight = i.overlay_light.zw / 15.0;
+    flw_vertexLight = i.light / 15.;
 }

src/main/resources/assets/flywheel/flywheel/instance/transformed.vert

@@ -2,6 +2,6 @@ void flw_instanceVertex(in FlwInstance i) {
     flw_vertexPos = i.pose * flw_vertexPos;
     flw_vertexNormal = i.normal * flw_vertexNormal;
     flw_vertexColor = i.color;
-    flw_vertexOverlay = i.overlay_light.xy;
+    flw_vertexOverlay = i.overlay;
-    flw_vertexLight = i.overlay_light.zw / 15.0;
+    flw_vertexLight = i.light / 15.;
 }

src/main/resources/assets/flywheel/flywheel/internal/common.frag

@@ -12,6 +12,8 @@ uniform sampler2D _flw_lightTex;
 
 out vec4 _flw_outputColor;
 
+in vec4 _flw_debugColor;
+
 void _flw_main() {
     flw_sampleColor = texture(_flw_diffuseTex, flw_vertexTexCoord);
     flw_fragColor = flw_vertexColor * flw_sampleColor;
@@ -35,7 +37,14 @@ void _flw_main() {
     }
 
     if (flw_material.useOverlay) {
-        vec4 overlayColor = texelFetch(_flw_overlayTex, flw_fragOverlay, 0);
+        // Need to clamp the overlay texture coords to sane coordinates because integer vertex attributes explode on
+        // some drivers for some draw calls.
+        // This can be removed once instancing uses sampler buffers, though
+        // we may need a solution for the internal vertex format. Perhaps
+        // pass as floats and convert to integers in the shader?
+        ivec2 actualCoord = clamp(flw_fragOverlay, ivec2(3), ivec2(10));
+
+        vec4 overlayColor = texelFetch(_flw_overlayTex, actualCoord, 0);
         color.rgb = mix(overlayColor.rgb, color.rgb, overlayColor.a);
     }
 
@@ -48,5 +57,14 @@ void _flw_main() {
         discard;
     }
 
+    switch (_flw_debugOverlay) {
+        case 1u:
+            color *= _flw_debugColor;
+            break;
+        case 2u:
+            color = _flw_debugColor;
+            break;
+    }
+
     _flw_outputColor = flw_fogFilter(color);
 }

src/main/resources/assets/flywheel/flywheel/internal/common.vert

@@ -1,6 +1,29 @@
 #include "flywheel:internal/fog_distance.glsl"
 
-void _flw_main(in FlwInstance instance) {
+// https://stackoverflow.com/a/17479300
+uint _flw_hash(in uint x) {
+    x += (x << 10u);
+    x ^= (x >> 6u);
+    x += (x << 3u);
+    x ^= (x >> 11u);
+    x += (x << 15u);
+    return x;
+}
+
+vec4 _flw_id2Color(in uint id) {
+    uint x = _flw_hash(id);
+
+    return vec4(
+        float(x & 0xFFu) / 255.0,
+        float((x >> 8u) & 0xFFu) / 255.0,
+        float((x >> 16u) & 0xFFu) / 255.0,
+        1.
+    );
+}
+
+out vec4 _flw_debugColor;
+
+void _flw_main(in FlwInstance instance, in uint stableInstanceID) {
     _flw_layoutVertex();
     flw_beginVertex();
     flw_instanceVertex(instance);
@@ -12,4 +35,19 @@ void _flw_main(in FlwInstance instance) {
     flw_distance = fogDistance(flw_vertexPos.xyz, flw_cameraPos, flw_fogShape);
 
     gl_Position = flw_viewProjection * flw_vertexPos;
+
+    switch (_flw_debugMode) {
+    case 0u:
+        _flw_debugColor = vec4(1.);
+        break;
+    case 1u:
+        _flw_debugColor = vec4(flw_vertexNormal * .5 + .5, 1.);
+        break;
+    case 2u:
+        _flw_debugColor = _flw_id2Color(stableInstanceID);
+        break;
+    case 3u:
+        _flw_debugColor = vec4(vec2((flw_vertexLight * 15.0 + 0.5) / 16.), 0., 1.);
+        break;
+    }
 }

src/main/resources/assets/flywheel/flywheel/internal/indirect/main.vert

@@ -32,5 +32,5 @@ void main() {
     uint objectIndex = objectIndices[gl_BaseInstance + gl_InstanceID];
     FlwInstance instance = _flw_unpackInstance(objects[objectIndex].instance);
 
-    _flw_main(instance);
+    _flw_main(instance, objectIndex);
 }

src/main/resources/assets/flywheel/flywheel/internal/instancing/main.vert

@@ -9,5 +9,5 @@ void main() {
 
     FlwInstance instance = _flw_unpackInstance();
 
-    _flw_main(instance);
+    _flw_main(instance, uint(gl_InstanceID));
 }

src/main/resources/assets/flywheel/flywheel/internal/uniforms/frame.glsl

@@ -29,6 +29,9 @@ layout(std140) uniform _FlwFrameUniforms {
 
     float flw_renderTicks;
     float flw_renderSeconds;
+
+    uint _flw_debugMode;
+    uint _flw_debugOverlay;
 };
 
 #define flw_cameraPos _flw_cameraPos.xyz