Performance Optimization

Performance Optimization

This guide covers advanced performance optimization techniques for rendering in Minecraft 26.1, focusing on GPU profiling, bottleneck analysis, and optimization strategies used in the vanilla codebase.

GPU Profiling and Bottleneck Analysis

Understanding Rendering Performance

The first step in optimization is understanding where performance bottlenecks occur. Minecraft 26.1 provides several tools and patterns for profiling rendering performance:

// Example: Basic timing setup
public class PerformanceProfiler {
    private long lastFrameTime;
    private float frameTime;

    public void beginFrame() {
        lastFrameTime = Blaze3D.getTime();
    }

    public void endFrame() {
        frameTime = (Blaze3D.getTime() - lastFrameTime) / 1_000_000.0f;
    }

    public float getFrameTime() {
        return frameTime;
    }
}

Identifying Common Bottlenecks

The most common rendering bottlenecks in Minecraft are:

1. Draw Call Overhead - Too many individual drawing operations
2. State Changes - Frequent changes to render state (shaders, textures)
3. Memory Bandwidth - Large amounts of data transferred to GPU
4. Fragment Shader Complexity - Expensive pixel processing

graph TD
    A[Rendering Performance Issue] --> B{Identify Bottleneck}
    B -->|High CPU Time| C[Too Many Draw Calls]
    B -->|High GPU Time| D[Complex Shaders]
    B -->|Memory Pressure| E[Large Buffers]
    B -->|State Changes| F[Frequent Binding]
    
    C --> G[Batch Similar Objects]
    D --> H[Simplify Shaders]
    E --> I[Optimize Buffers]
    F --> J[Reduce State Changes]

Distance-Based Prioritization

Minecraft uses distance-based task prioritization to optimize rendering performance:

net.minecraft.client.renderer.chunk.CompileTaskDynamicQueue

public synchronized SectionRenderDispatcher.RenderSection.CompileTask poll(final Vec3 cameraPos) {
    SectionRenderDispatcher.RenderSection.CompileTask bestInitialCompileTask = null;
    SectionRenderDispatcher.RenderSection.CompileTask bestRecompileTask = null;
    double bestInitialCompileDistance = Double.MAX_VALUE;
    double bestRecompileDistance = Double.MAX_VALUE;

    // Find closest tasks for both initial and recompile
    for (int i = 0; i < this.size(); ++i) {
        SectionRenderDispatcher.RenderSection.CompileTask task = this.getTask(i);
        double distance = task.getDistanceFromCamera(cameraPos);

        if (task.isInitialCompile()) {
            if (distance < bestInitialCompileDistance) {
                bestInitialCompileDistance = distance;
                bestInitialCompileTask = task;
                bestInitialCompileTaskIndex = i;
            }
        } else {
            if (distance < bestRecompileDistance) {
                bestRecompileDistance = distance;
                bestRecompileTask = task;
                bestRecompileTaskIndex = i;
            }
        }
    }

    // Prioritize based on distance and quota
    if (!hasRecompileTask || hasInitialCompileTask &&
        (this.recompileQuota <= 0 || !(bestRecompileDistance < bestInitialCompileDistance))) {
        this.recompileQuota = 2;
        return this.removeTaskByIndex(bestInitialCompileTaskIndex);
    } else {
        this.recompileQuota--;
        return this.removeTaskByIndex(bestRecompileTaskIndex);
    }
}

Advanced Batching Techniques

State-Based Batching

The most effective optimization is grouping similar objects together to minimize state changes:

// Example: Advanced batching system
public class AdvancedBatchRenderer {
    private final Map<RenderState, List<RenderableObject>> renderBatches = new HashMap<>();

    public void addObject(RenderableObject object) {
        RenderState state = object.getRenderState();
        renderBatches.computeIfAbsent(state, k -> new ArrayList<>()).add(object);
    }

    public void renderAll(PoseStack poseStack) {
        RenderSystem.assertOnRenderThread();

        for (Map.Entry<RenderState, List<RenderableObject>> entry : renderBatches.entrySet()) {
            RenderState state = entry.getKey();
            List<RenderableObject> batch = entry.getValue();

            // Apply render state once for entire batch
            state.apply();

            // Render all objects in batch
            for (RenderableObject object : batch) {
                object.render(poseStack);
            }
        }

        renderBatches.clear();
    }
}

Dynamic Buffer Resizing

Optimize buffer usage with intelligent resizing strategies:

net.minecraft.client.renderer.DynamicUniformStorage

private void resizeBuffers(final int newCapacity) {
    this.capacity = newCapacity;
    this.oldBuffers.add(this.ringBuffer);
    this.ringBuffer = new MappableRingBuffer(() -> this.label + " x" + this.blockSize,
                                               130, this.blockSize * newCapacity);
}

private int writeUniforms(final int firstIndex, final int count, final byte[] uniforms) {
    int bytesWritten = 0;

    while (bytesWritten < count) {
        int availableBytes = this.ringBuffer.availableBytes();
        if (availableBytes == 0) {
            this.increaseRingBuffer(this.blockSize);
            continue;
        }

        int bytesToWrite = Math.min(count - bytesWritten, availableBytes);
        this.ringBuffer.writeBytes(uniforms, bytesWritten, bytesToWrite);
        bytesWritten += bytesToWrite;
    }

    return bytesWritten;
}

Frustum Culling Optimization

Implement efficient frustum culling to avoid rendering off-screen objects:

// Example: Advanced frustum culling
public class FrustumCuller {
    private final Plane[] frustumPlanes = new Plane[6];

    public void updateFrustum(Matrix4f projectionViewMatrix) {
        // Extract frustum planes from projection-view matrix
        for (int i = 0; i < 6; i++) {
            frustumPlanes[i] = extractPlane(projectionViewMatrix, i);
        }
    }

    public boolean isInFrustum(BoundingBox box) {
        for (Plane plane : frustumPlanes) {
            if (!box.isOnOrForwardPlane(plane)) {
                return false;
            }
        }
        return true;
    }

    public List<RenderableObject> cullObjects(List<RenderableObject> objects) {
        return objects.stream()
            .filter(obj -> isInFrustum(obj.getBoundingBox()))
            .collect(Collectors.toList());
    }
}

Frame Rate Optimization

Level of Detail (LOD) Systems

Implement LOD to reduce rendering overhead for distant objects:

// Example: LOD system for entities
public class EntityLODSystem {
    private static final float[] LOD_DISTANCES = {0.0f, 16.0f, 32.0f, 64.0f};
    private static final int[] LOD_LEVELS = {4, 3, 2, 1};

    public int getLODLevel(Entity entity, Vec3 cameraPos) {
        double distance = entity.position().distanceTo(cameraPos);

        for (int i = 0; i < LOD_DISTANCES.length - 1; i++) {
            if (distance >= LOD_DISTANCES[i] && distance < LOD_DISTANCES[i + 1]) {
                return LOD_LEVELS[i];
            }
        }
        return LOD_LEVELS[LOD_LEVELS.length - 1];
    }

    public void renderWithLOD(Entity entity, int lodLevel, PoseStack poseStack) {
        switch (lodLevel) {
            case 4: // Ultra quality - full detail
                renderFullDetail(entity, poseStack);
                break;
            case 3: // High quality - reduced animation
                renderHighDetail(entity, poseStack);
                break;
            case 2: // Medium quality - simplified model
                renderMediumDetail(entity, poseStack);
                break;
            case 1: // Low quality - bounding box only
                renderLowDetail(entity, poseStack);
                break;
        }
    }
}

Adaptive Quality Settings

Adjust rendering quality based on performance:

// Example: Adaptive quality system
public class AdaptiveQualityManager {
    private float targetFrameTime = 16.67f; // 60 FPS target
    private float currentFrameTime;
    private QualityLevel currentQuality = QualityLevel.HIGH;

    public enum QualityLevel {
        ULTRA, HIGH, MEDIUM, LOW
    }

    public void updateQuality(float frameTime) {
        this.currentFrameTime = frameTime;

        if (frameTime > targetFrameTime * 1.5f) {
            // Performance is poor, reduce quality
            if (currentQuality != QualityLevel.LOW) {
                currentQuality = QualityLevel.values()[currentQuality.ordinal() + 1];
                applyQualitySettings(currentQuality);
            }
        } else if (frameTime < targetFrameTime * 0.8f) {
            // Performance is good, increase quality
            if (currentQuality != QualityLevel.ULTRA) {
                currentQuality = QualityLevel.values()[currentQuality.ordinal() - 1];
                applyQualitySettings(currentQuality);
            }
        }
    }

    private void applyQualitySettings(QualityLevel level) {
        switch (level) {
            case ULTRA:
                RenderSystem.enableCull();
                setMaxRenderDistance(32);
                enableShadows(true);
                break;
            case HIGH:
                RenderSystem.enableCull();
                setMaxRenderDistance(24);
                enableShadows(true);
                break;
            case MEDIUM:
                RenderSystem.enableCull();
                setMaxRenderDistance(16);
                enableShadows(false);
                break;
            case LOW:
                RenderSystem.disableCull();
                setMaxRenderDistance(8);
                enableShadows(false);
                break;
        }
    }
}

Memory Bandwidth Optimization

Buffer Arena Management

Use buffer arenas to minimize memory fragmentation and improve performance:

// Example: Buffer arena for efficient memory management
public class BufferArena {
    private final List<ByteBufferBuilder> arenas = new ArrayList<>();
    private final int arenaSize;
    private int currentArena = 0;

    public BufferArena(int arenaSize, int arenaCount) {
        this.arenaSize = arenaSize;
        for (int i = 0; i < arenaCount; i++) {
            arenas.add(new ByteBufferBuilder(arenaSize));
        }
    }

    public ByteBufferBuilder getNextArena() {
        ByteBufferBuilder arena = arenas.get(currentArena);
        if (arena.remaining() < arenaSize / 4) {
            currentArena = (currentArena + 1) % arenas.size();
            arena = arenas.get(currentArena);
            arena.clear();
        }
        return arena;
    }

    public void reset() {
        currentArena = 0;
        for (ByteBufferBuilder arena : arenas) {
            arena.clear();
        }
    }
}

Texture Atlas Optimization

Optimize texture usage to minimize texture binding changes:

// Example: Texture atlas management
public class TextureAtlasOptimizer {
    private final Map<String, TextureAtlas> atlases = new HashMap<>();
    private final Map<String, String> textureToAtlas = new HashMap<>();

    public void organizeTextures(List<String> textures) {
        // Group textures by type and usage frequency
        Map<String, List<String>> groupedTextures = groupTexturesByType(textures);

        for (Map.Entry<String, List<String>> entry : groupedTextures.entrySet()) {
            String type = entry.getKey();
            List<String> typeTextures = entry.getValue();

            // Create optimized atlas for this texture type
            TextureAtlas atlas = createOptimizedAtlas(typeTextures);
            atlases.put(type, atlas);

            // Map individual textures to their atlas
            for (String texture : typeTextures) {
                textureToAtlas.put(texture, type);
            }
        }
    }

    public void bindAtlasForTexture(String texture) {
        String atlasType = textureToAtlas.get(texture);
        if (atlasType != null) {
            TextureAtlas atlas = atlases.get(atlasType);
            RenderSystem.setShaderTexture(0, atlas.getTextureId());
        }
    }
}

Performance Monitoring

Real-time Performance Metrics

Implement real-time performance monitoring for debugging:

// Example: Performance metrics collection
public class PerformanceMetrics {
    private final Map<String, Long> renderTimes = new HashMap<>();
    private final Map<String, Integer> drawCalls = new HashMap<>();
    private final Map<String, Integer> stateChanges = new HashMap<>();

    public void beginTimer(String operation) {
        renderTimes.put(operation, Blaze3D.getTime());
    }

    public void endTimer(String operation) {
        long startTime = renderTimes.get(operation);
        long endTime = Blaze3D.getTime();
        renderTimes.put(operation, endTime - startTime);
    }

    public void recordDrawCall(String renderType) {
        drawCalls.merge(renderType, 1, Integer::sum);
    }

    public void recordStateChange(String stateType) {
        stateChanges.merge(stateType, 1, Integer::sum);
    }

    public void printMetrics() {
        System.out.println("=== Performance Metrics ===");

        System.out.println("\nRender Times (ms):");
        renderTimes.forEach((op, time) ->
            System.out.printf("  %s: %.2f%n", op, time / 1_000_000.0));

        System.out.println("\nDraw Calls:");
        drawCalls.forEach((type, count) ->
            System.out.printf("  %s: %d%n", type, count));

        System.out.println("\nState Changes:");
        stateChanges.forEach((type, count) ->
            System.out.printf("  %s: %d%n", type, count));
    }
}

Performance Profiling Tools

Create profiling tools to identify optimization opportunities:

// Example: Advanced profiler
public class RenderProfiler {
    private final Stack<TimingStack> timingStack = new Stack<>();
    private final Map<String, ProfilingData> profilingData = new HashMap<>();

    public void push(String operation) {
        TimingStack stack = new TimingStack(operation, Blaze3D.getTime());
        timingStack.push(stack);
    }

    public void pop() {
        if (!timingStack.isEmpty()) {
            TimingStack stack = timingStack.pop();
            long endTime = Blaze3D.getTime();

            profilingData.computeIfAbsent(stack.operation, k -> new ProfilingData())
                .addSample(endTime - stack.startTime);
        }
    }

    public List<String> getBottlenecks() {
        return profilingData.entrySet().stream()
            .sorted((a, b) -> Long.compare(b.getValue().getAverageTime(),
                                          a.getValue().getAverageTime()))
            .limit(5)
            .map(Map.Entry::getKey)
            .collect(Collectors.toList());
    }

    private static class TimingStack {
        final String operation;
        final long startTime;

        TimingStack(String operation, long startTime) {
            this.operation = operation;
            this.startTime = startTime;
        }
    }

    private static class ProfilingData {
        private final List<Long> samples = new ArrayList<>();
        private long totalSamples = 0;

        void addSample(long sample) {
            samples.add(sample);
            totalSamples++;
        }

        long getAverageTime() {
            return samples.stream().mapToLong(Long::longValue).sum() / totalSamples;
        }
    }
}

Common Optimization Patterns

Precomputed Geometry

Precompute static geometry to reduce per-frame calculations:

// Example: Precomputed mesh system
public class PrecomputedMesh {
    private final Mesh mesh;
    private final BoundingBox boundingBox;

    public PrecomputedMesh(List<Vector3f> vertices, List<Integer> indices) {
        this.mesh = createMesh(vertices, indices);
        this.boundingBox = calculateBoundingBox(vertices);
    }

    public void render(PoseStack poseStack) {
        // Simply bind and render precomputed geometry
        mesh.bind();
        mesh.render();
    }

    public boolean isVisible(FrustumCuller frustumCuller, PoseStack poseStack) {
        BoundingBox transformedBox = boundingBox.transform(poseStack.last().pose());
        return frustumCuller.isInFrustum(transformedBox);
    }
}

Lazy Evaluation

Use lazy evaluation to defer expensive calculations until needed:

// Example: Lazy computation system
public class Lazy<T> {
    private final Supplier<T> supplier;
    private T value = null;
    private boolean computed = false;

    public Lazy(Supplier<T> supplier) {
        this.supplier = supplier;
    }

    public T get() {
        if (!computed) {
            value = supplier.get();
            computed = true;
        }
        return value;
    }

    public void invalidate() {
        computed = false;
        value = null;
    }
}

// Usage example for expensive calculations
public class EntityRenderer {
    private final Lazy<ComplexModel> cachedModel = new Lazy<>(() -> {
        // Expensive model computation
        return computeExpensiveModel();
    });

    public void render(Entity entity) {
        ComplexModel model = cachedModel.get();
        model.render();
    }
}

Best Practices

Performance Guidelines

1. Profile First: Always measure before optimizing
2. Batch Smartly: Group objects by render state, not just by type
3. Minimize State Changes: Reduce shader, texture, and buffer bindings
4. Use LOD: Implement distance-based detail reduction
5. Precompute When Possible: Cache expensive calculations
6. Monitor Memory: Watch for memory leaks and excessive allocations

Common Pitfalls to Avoid

// ❌ WRONG - Excessive state changes
public void renderInefficiently(List<Entity> entities) {
    for (Entity entity : entities) {
        RenderSystem.setShaderTexture(0, entity.getTexture());
        RenderSystem.setShaderColor(1.0f, 1.0f, 1.0f, 1.0f);
        entity.render();
    }
}

// ✅ CORRECT - Batch by texture
public void renderEfficiently(List<Entity> entities) {
    Map<ResourceLocation, List<Entity>> grouped = entities.stream()
        .collect(Collectors.groupingBy(Entity::getTexture));

    for (Map.Entry<ResourceLocation, List<Entity>> entry : grouped.entrySet()) {
        RenderSystem.setShaderTexture(0, entry.getKey());
        RenderSystem.setShaderColor(1.0f, 1.0f, 1.0f, 1.0f);

        for (Entity entity : entry.getValue()) {
            entity.render();
        }
    }
}

Next Steps

• Multi-threaded Rendering - Advanced thread safety and async patterns
• Memory Management - Advanced buffer and resource management
• Advanced Shader Techniques - Optimized shader development

Common Issues

1. Over-optimization: Don’t optimize code that isn’t actually a bottleneck
2. Premature Optimization: Profile first, then optimize based on data
3. Micro-optimizations: Focus on architectural improvements first
4. Ignoring Frame Time: Optimize for consistent frame rates, not just maximum FPS
5. Memory vs. Speed: Balance memory usage against rendering performance