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Lumen is a Vulkan ray tracing framework that contains a variety of variance reduction techniques. Its aim is to accelerate some of the well-known rendering techniques in computer graphics literature with the help of the ray tracing hardware in modern GPUs. All the techniques Lumen implements run fully on the GPU.

• Unidirectional Path Tracer with Multiple Importance Sampling (Path)
• Bidirectional Path Tracer (BDPT)
• Stochastic Progressive Photon Mapping (SPPM)
• Vertex Connection and Merging (VCM)
• Primary Sample Space Metropolis Light Transport (PSSMLT)
• Combined VCM + MLT Integrator (VCMMLT)
• ReSTIR
• ReSTIR GI
• ReSTIR PT / GRIS
• DDGI (Real time)
• FFT Convolution Bloom

• Diffuse, mirror, glass, conductor, dielectric and Disney Principled BSDF
• Spot (point), polygonal and directional lights
• JSON-based scene system
• Modified Mitsuba parser
• A lightweight Vulkan abstraction layer from scratch
• EXR output (F10)
• On-the-fly RMSE computation
• SPIRV reflection
• Render graph support with experimental Vulkan features
  • Automatic resource and synchronization management
  • Binding inference based on shader reflection results
  • Simple builder pattern

With the recently integrated render graph, Lumen uses some of the more experimental Vulkan features. These are namely,

• Templated push descriptors (may be problematic with AMD)
• Event-based syncronization (via syncronization2 API, available from Vulkan 1.3)
  • Experimental feature, may not work depending on your driver (May need Vulkan beta drivers on Nvidia)
  • Enabled viause_events flag in the Render Graph settings. (SeeRenderGraphSettings inRenderGraphTypes.h andRayTracer.cpp)

To build Lumen, start cloning the repository with

git clone --recursive https://github.com/yuphin/Lumen.git

• Vulkan SDK
• Turing+ or RDNA2 GPU
• CMake 3.4 or above (Credits to@Lachei for porting the project to CMake and testing it on Linux)

Some of the sample scenes can be found in thescenes/ directory.Sample scene files with various integrators can be found in thescenes/cornell_box/ directory.

To load a scene file simply run:

Lumen.exe<scene_file>

The best way to get started is to take a look at the unidirectional path tracer implemented insrc/Raytracer/Path.cpp and gradually explore the other integrators. From there, you can focus on the related shaders that are located in thesrc/shaders folder.

• Physically Based Rendering: From Theory to Implementation
• Light Transport Simulation with Vertex Connection and Merging
• Spatiotemporal Reservoir Resampling for Real-time Ray Tracing with Dynamic Direct Lighting
• ReSTIR GI: Path Resampling for Real-Time Path Tracing
• Robust Monte Carlo Methods for Light Transport Simulation
• Robust Light Transport Simulation via Metropolised Bidirectional Estimators
• Dynamic Diffuse Global Illumination with Ray-Traced Irradiance Fields