The Narumi renderer is an offline physically based renderer for research and self-education purpose. Narumi was created almost completely from scratch (except for the building blocks of asset loading). Currently It covers a relatively basic set of features. However, once the foundation has been laid, I should be ready to implement a lot of more advanced techniques. Integration with the recent real-time raytracing technologies is also on the roadmap.

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Current feature set

• Bounding volume hierarchy (BVH): Hierarchical Linear BVH and binned-SAH BVH

• Quasi Monte Carlo samplers.

• Direct lighting integrator.

• Incremental path tracing integrator with Russian roulette.

• Bidirectional path tracing integrator (with multiple importance sampling).

• Volumetric path tracing integrator.

• Area lights (polygonal mesh) and punctual lights.

• Image-based lighting.

• Basic matte, mirror (specular reflection) and glass (specular transmission) material.

• Microfacet-based material (GGX), both reflection and transmission. Importance sample based on visible NDF function.

• Texturing with ray differential anti-aliasing; Bump mapping.

• Homogeneous participant media with common phase functions (isotropic / Henyey-Greenstein).

• Subsurface scattering support based on photon beam diffusion.

• Object instancing.

• CPU parallelization via multithreading.

• Custom scene representation to define everything including integrator, camera, geometry, lighting, and material. Conversion between source asset and custom representation is provided.

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Blog posts:​

• Subsurface scattering implementation in Narumi.

 

Future roadmap

• More advanced integrators such as VCM and MLT (Multiplexed MLT).

• More advanced material such as:

  • Specular microstructure, such as Yan, Ling-Qi, et al. "Position-normal distributions for efficient rendering of specular microstructure."

  • Multiple-scattering material, such as Heitz, Eric, et al. "Multiple-scattering microfacet BSDFs with the Smith model."

  • Layered material, such as Belcour Laurent, "Efficient Rendering of Layered Materials using an Atomic Decomposition with Statistical Operators".

• More (heterogeneous) participant media. Possibly OpenVDB integration.

• More subsurface scattering, such as Frisvad, Jeppe Revall, Toshiya Hachisuka, and Thomas Kim Kjeldsen. "Directional dipole model for subsurface scattering."

• Sorted raytracing / deferred shading.

• Adaptive sampling.

• Monte Carlo denoising, such as Schied, Christoph, et al. "Spatiotemporal variance-guided filtering: real-time reconstruction for path-traced global illumination."

• Real-time ray-tracing (Direct 12 DXR / Nvidia RTX).

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Gallery

Above and below are some images rendered by Narumi demonstrating different features. Hopefully the gallery will keep growing ;)

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Asset sources:

• Testing "knob" modified from https://github.com/lighttransport/lighttransportequation-orb.

• Textures from FreePBR (https://freepbr.com).

• HDR Environment maps from http://gl.ict.usc.edu/Data/HighResProbes/

• Cornell box, bunny, sculpture head modified from McGuire Computer Graphics Archive (http://casual-effects.com/data/).

• Exotic car purchased from Turbosquid.