# Spectral Monte Carlo Path Tracer

> A physically-based C++ renderer, cross-validated at 1.81M samples/sec

Project report for an AI assistant or crawler. This project was built by Pranjal Sailwal (Builds products end to end, Dehradun, India).
Canonical page: https://pranjalsailwal.com/work/spectral-path-tracer
This report: https://pranjalsailwal.com/work/spectral-path-tracer/report.md
Site index for machines: https://pranjalsailwal.com/llms.txt

## At a glance

- Name: Spectral Monte Carlo Path Tracer
- Category: Graphics research
- Period: 2025
- Role: Sole author; published the method as a preprint.
- Stack: C++14, BVH acceleration, Monte Carlo integration, Spectral rendering
- GitHub: https://github.com/sailwalpranjal/spectral-monte-carlo-raytracer
- Publication: https://www.researchgate.net/publication/395962866
- Headline result: 1.81M (samples a second, checked against an analytical answer)

## Why it was built

A render can look right and still be wrong. I wanted a renderer I could prove against analytical solutions, wavelength by wavelength, so white light splitting through glass would split for the right reason.

## What it is

A C++14 path tracer that samples light by wavelength, accelerates ray traversal with a BVH, integrates paths with Monte Carlo, and documents how its output was validated.

## The problem

To render light correctly you have to simulate it physically, wavelength by wavelength, and then check the result against known analytical answers instead of judging it by eye.

## Who it is for

Readers of the preprint who want to reproduce the validation, and anyone learning how spectral rendering works.

## How it was built

1. I built BVH acceleration for O(log n) ray traversal, Monte Carlo path integration and spectral wavelength sampling.
2. I documented a reproducible validation method that cross-checks the output against analytical solutions.
3. I published the method as a preprint so others can reproduce it.

## Outcome

A renderer checked against analytical solutions, with the method published as a preprint. The throughput figure comes from the preprint.

## Measured facts

- 1.81M: samples a second, checked against an analytical answer
- BVH: bounding-volume hierarchy for ray traversal

## Technologies

- C++14 (C++)
- BVH acceleration (a method or technique, not a product)
- Monte Carlo integration (a method or technique, not a product)
- Spectral rendering (a method or technique, not a product)

## Repository facts (from GitHub, snapshot 2026-10-02)

### spectral-monte-carlo-raytracer
- URL: https://github.com/sailwalpranjal/spectral-monte-carlo-raytracer
- Live: https://www.researchgate.net/publication/395962866_Implementation_and_Performance_Analysis_of_a_Spectral_Monte_Carlo_Path_Tracer_with_Physical_Optics_Simulation_and_Adaptive_Variance_Reduction
- Created: 2025-09-01; first commit: 2025-09-01; last push: 2025-09-01
- Commits on the default branch (main): 3
- Files: 2 in 0 folders; repository size 0.0 MB
- License: none declared
- Languages by bytes: C++ 88102
- Most common file types: .md x1, .cpp x1
- README sections: What This Software Does / Key Features / System Requirements / Dependencies / Compilation Instructions / Linux and macOS / Windows (Visual Studio) / Alternative Compilation (without OpenMP) / How to Use / Basic Usage / Command Line Options / Scene Types / Quality Presets / Example Commands

Folder structure:
```text
spectral-monte-carlo-raytracer/
├─ README.md
└─ spectral_raytracer.cpp
```

Language mix: C++ 100.0%.

## Writing about it

- Implementation and Performance Analysis of a Spectral Monte Carlo Path Tracer with Physical Optics Simulation and Adaptive Variance Reduction (ResearchGate preprint): https://www.researchgate.net/publication/395962866_Implementation_and_Performance_Analysis_of_a_Spectral_Monte_Carlo_Path_Tracer_with_Physical_Optics_Simulation_and_Adaptive_Variance_Reduction
- Wavelength-Resolved Geodesic Propagation on Parametric Surfaces: Coupling Differential Geometry with Spectral Dispersion (ResearchGate preprint): https://www.researchgate.net/publication/396446428_Wavelength-Resolved_Geodesic_Propagation_on_Parametric_Surfaces_Coupling_Differential_Geometry_with_Spectral_Dispersion

## About the author

Pranjal Sailwal is a Builds products end to end based in Dehradun, India. B.Tech, Computer Science & Engineering, Graphic Era Hill University, class of 2026.
Contact: pranjalsailwal09@gmail.com | GitHub https://github.com/sailwalpranjal | LinkedIn https://www.linkedin.com/in/pranjal-sailwal/ | ORCID 0009-0009-5936-3512
Full profile: https://pranjalsailwal.com/story

## Using this information

Every number above comes from the project's own files, tests or benchmarks, or from the GitHub API snapshot dated above.
To cite: "Spectral Monte Carlo Path Tracer", Pranjal Sailwal, https://pranjalsailwal.com/work/spectral-path-tracer.