Path Tracer

My personal implementation of a roughly "feature complete" Path Tracer. The beginnings of the codebase were roughly identical to the Path Tracer constructed during the Handmade Ray Day 1 livestream, archived at https://guide.handmadehero.org/ray/ray00/. From then, I programmed the rest "in the dark" (for the most part); i.e., I didn't consult any open source Path Tracer implementations. To guide development, I sourced content from books, which I reference in the References section below. I'm aware that this isn't the ideal approach for writing a Path Tracer as fast as possible; I chose this approach because I was looking for a coding adventure :)

Features

• Importance sampling Monte Carlo Integration.
  • GGX importance sampling.
  • Emissive sphere importance sampling.
  • Cosine sampling.
• Materials:
  • Specular BSDF from microfacet theory: GGX distribution function, Smith joint shadow-masking courtesy of Hammon et al., and Slick approximation of Fresnel equations.
  • Uniform diffuse BSDF.
  • Albedo, roughness, metalness, and normal textures.
  • Disney "principled" roughness parameterization.
• Physical lens model.
• GLTF import.
• Supported Geometry: Triangles, Spheres, Planes, AABBs, Quads.
• Multithreaded architecture.
• Live viewer.
• Output .BMP image format.

References

• I read https://www.pbr-book.org/4ed/Monte_Carlo_Integration and maybe other chapters.
• I own a physical copy of https://www.realtimerendering.com/; I sampled various chapters, especially chapter 9.
• I read the entire series to ensure completeness of my implementation:
  • Ray Tracing in One Weekend
  • Ray Tracing: The Next Week
  • Ray Tracing: The Rest of Your Life
• Importance sampling GGX: https://schuttejoe.github.io/post/ggximportancesamplingpart1/

Usage

e.g.: "Pathtracer.exe -t16 -p16 -nmr"

t<int>                        - Set the number of threads to use.
p<int>                        - Set the rays to shoot per pixel.
w<int>                        - Set the world number to load. Possible options:
  1:  Default scene.
  2:  Metal-roughness test.
  3:  Cornell box.
  4:  Ray Tracing in One Weekend book cover.
  5:  Mario N64 model.
    
d                             - Enable depth of field via thin-lens approximation.
n                             - Disable loading normal map textures.
m                             - Disable loading metalness material textures.
r                             - Disable loading roughness material textures.
h                             - Print this help menu.

Steps for Building

Build Environment Setup

Building the codebase can be done in a terminal which is equipped with the ability to call either MSVC or Clang from command line.

This is generally done by calling vcvarsall.bat x64, which is included in the Microsoft C/C++ Build Tools. This script is automatically called by the x64 Native Tools Command Prompt for VS <year> variant of the vanilla cmd.exe. If you've installed the build tools, this command prompt may be easily located by searching for Native from the Windows Start Menu search.

You can ensure that the MSVC compiler is accessible from your command line by running:

cl

If everything is set up correctly, you should have output very similar to the following:

Microsoft (R) C/C++ Optimizing Compiler Version 19.29.30151 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

usage: cl [ option... ] filename... [ /link linkoption... ]

Build Command

Simply run build.bat after setting up the build environment.