CherryPip

by Fiona Wright

Info

D3D12 Graphics Engine with a focus on Path-Tracing / Spectral-Tracing using RayQuery.
Built for fun and to further my skills in the graphics programming field.
Trying to work on it when I have free time from college.

Uses CMAKE for the build system.
C++, HLSL and Python are the main languages.

Third-Party Tools

• Dear ImGui (GUI)
• spng (PNG Loader)
• tinyddsloader (DDS Loader)
• texconv (PNG/JPG -> DDS Build Step)
• zlib/fastgltf (GLTF Loader)
• WinPixEventRuntime (GPU Events/Markers)

Features

Engine

• Repository split between engine (HWI + System + Render) and Apps (SceneStudio)
• Python Execution at runtime for data analysis / debugging
• Hot reloading for shaders
• Set up scene configs and switch between them at runtime seamlessly
• Scene GUI tab where you can modify each objects transform, material, etc

Forward + Deferred Render Backends

• Microfacet lighting model + Irradiance IBL
• Rotatable cubemap skybox that has parity with path tracer backend
• Many different debug view modes (WorldPos, Normals, Tangents, Roughness, UV, Lambert, Albedo, etc) (Over 20)
• Ability to render lines for debugging directions/axes/etc

Path Tracer Render Backend

• Fully deterministic and seeded
• Russian Roulette, Firefly Threshold, Cosine Importance Sampling
• Furnace Tests for debugging
• Depth of Field
• Independent, Halton, Apple Halton and Owen-Scrambled Halton RNG sampling strategies
• Environment maps with support for Panoramic and Octohedral Equal-Area (Rotatable at runtime)
• Directional lighting + GPU max parallel search on the EA Environment Map to set automatically direction to where luminance is highest
• Denoising (Box, Gaussian, Median, Edge-Avoiding A-Trous) using GBuffer pre-pass
• Proper BSDF / BRDF / BTDF lighting model system

Lighting Models

• BRDF Diffuse: Lambertian
• MM: GGX Smith
• MM: GGX Smith Anisotropic
• MM: GGX VCavity VNDF
• MM: GGX Smith VNDF
• MM: GGX Smith Anisotropic VNDF
• All MMs work for both BRDF Specular & BTDF

Debug Tools

Readback System

• Click on a pixel and see its RGBA output value in the GUI
• Automatically collect a pixels value over multiple frames and then plot it in a histogram

Info Output System

• Output different variables inside the path-tracer for each pixel (Normals, Albedo, HitDist, RNG, FirstBounceDirection, etc) (Over 30)

Convergence System

• Take snapshots of the path-tracer output into 2 slots and find the RMSE between them with a compute shader
• Generate golden images, save them as PNGs and load them into slot A
• Automatically take snapshots into slot B every frame and compute the RMSE. Then plot RMSE convergence graphs using python

Path Visualizer System

• Click on a pixel to have all rays shot from that pixel next frame store their positions at each bounce
• That data is then converted into coloured lines so you can follow the rays path

Spectral Tracer Render Backend

• CIE2006 + Mallet&Yuksel2019 spectral primary decomposition
• Multi-Lobe gaussian curve fitting for CIE_XYZbar & D65 Illuminant curves
• Logistic curve fitting for CIE spectral primaries
• Sellmeier curve fitting for material reflective index spectra
• Many different debug spectra tests
• Zero round-trip error
• Full-Spectrum, Single-Wavelength and Hero-Sampling spectral sampling modes
• Lambert and microfacet BSDF lighting models
• Maxwell fresnell for dielectrics, conductors and glass materials

History

Progress as of 29/10/25:

Progress as of 08/11/25:

Progress as of 09/11/25:

Progress as of 10/01/26:

Progress as of 18/01/26:

Progress as of 25/01/26:

Progress as of 29/01/26:

Progress as of 18/02/26:

Progress as of 21/02/26:

Progress as of 11/03/26:

Progress as of 23/03/26:

Progress as of 29/03/26: