Understanding AnKi Engine in Large Projects

Vulkan-Centric Rendering

AnKi's rendering core leverages Vulkan's explicit control over GPU resources. While this enables fine-grained performance tuning, it also requires precise synchronization to avoid GPU/CPU pipeline stalls.

Subsystem Integration

  • Deferred shading and post-processing pipelines.
  • Multi-threaded resource loading and scene updates.
  • Custom shaders integrated via GLSL or SPIR-V.

Architectural Background

Render Graph System

AnKi's render graph automates GPU pass scheduling and dependency tracking. Misconfigured passes or circular dependencies can cause frame latency spikes or undefined rendering order.

Asset Streaming and Memory

Assets are streamed asynchronously. Improper buffer reuse or failure to free staging buffers can lead to GPU VRAM fragmentation and excessive paging.

Diagnostics

Detecting GPU Stalls

Use Vulkan validation layers with VK_EXT_debug_utils to trace synchronization points. Identify long vkQueueSubmit durations or barriers with high wait times.

# Enable validation layers in AnKi config
ANKI_VK_DEBUG=1 ./MyAnKiApp

Profiling Frame Graph Execution

Instrument the render graph to log pass execution times. Identify slow passes and investigate shader complexity or overdraw.

Monitoring Memory Usage

Leverage tools like NVIDIA Nsight Graphics or AMD Radeon GPU Profiler to track VRAM allocations and detect leaks or fragmentation patterns.

Common Pitfalls

Improper Barrier Usage

Placing global memory barriers between every pass forces the GPU to flush caches unnecessarily, tanking performance.

Overloaded Asset Streaming

Loading too many large assets simultaneously can saturate IO and block other subsystems, leading to noticeable stalls.

Step-by-Step Fixes

1. Optimize Synchronization

Replace global barriers with fine-grained image and buffer barriers targeting only affected resources.

// Example: Use subresource range to limit barrier scope
VkImageMemoryBarrier barrier = {};
barrier.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;

2. Profile and Reduce Overdraw

Use engine debug views to visualize overdraw. Reduce overlapping geometry and optimize material shaders for early-z rejection.

3. Manage Streaming Load

Implement priority queues for asset loading, ensuring critical resources are loaded before background assets.

4. Debug Render Graph Issues

Run the render graph in debug mode to detect invalid pass dependencies before runtime execution.

5. Optimize Shader Compilation

Precompile shaders into SPIR-V and cache them to avoid runtime compilation stalls during gameplay.

Best Practices

  • Regularly profile frame graphs to detect regressions early.
  • Use asynchronous compute where possible to overlap work.
  • Limit barrier scopes and avoid unnecessary full-pipeline stalls.
  • Implement streaming budgets to keep IO predictable.
  • Test on target hardware early to uncover driver-specific issues.

Conclusion

AnKi Engine's Vulkan-first design offers unmatched control and performance potential, but demands disciplined resource management and synchronization strategies. By proactively profiling, minimizing unnecessary barriers, and managing asset streaming intelligently, developers can ensure stable frame times and optimal GPU utilization—even in large, complex scenes. Treating the render graph and streaming systems as first-class components in your performance strategy is essential for delivering high-quality real-time experiences.

FAQs

1. How can I detect circular dependencies in the render graph?

Enable AnKi's debug render graph mode. It will log dependency cycles, allowing you to refactor pass order or split passes.

2. Why does my VRAM usage keep increasing during gameplay?

This is usually due to unreleased staging buffers or persistent textures never being freed. Use GPU profiling tools to identify allocations that don't decrease over time.

3. Can AnKi handle multi-GPU setups efficiently?

Yes, but it requires explicit configuration. Work must be split manually or via custom render graph modifications to target different devices.

4. What's the best way to avoid shader compilation hitches?

Precompile all shaders to SPIR-V during the build process and use a persistent shader cache.

5. How do I debug frame time spikes in AnKi?

Profile both CPU and GPU timelines using Nsight Systems. Look for synchronization points, IO stalls, or long shader executions in slow frames.