Toy Path Tracer

Toy path tracer for my own learning purposes, using various approaches/techs. Somewhat based on Peter Shirley's Ray Tracing in One Weekend minibook (highly recommended!), and on Kevin Beason's smallpt.

I decided to write blog posts about things I discover as I do this, currently:

• Part 0: Intro
• Part 1: Initial C++ and walkthrough
• Part 2: Fix stupid performance issue
• Part 3: C#, Unity and Burst
• Part 4: Correctness fixes and Mitsuba
• Part 5: simple GPU version via Metal
• Part 6: simple GPU version via D3D11
• Part 7: initial C++ SIMD & SoA
• Part 8: SSE SIMD for HitSpheres
• Part 9: ryg optimizes my code
• Part 10: Update all implementations to match
• Part 11: Buffer-oriented approach on CPU
• Part 12: Buffer-oriented approach on GPU D3D11
• Part 13: GPU thread group data optimization

Right now: can only do spheres, no bounding volume hierachy of any sorts, a lot of stuff hardcoded.

Implementations I'm playing with (again, everything is in toy/learning/WIP state; likely suboptimal) are below. These are all on a scene with ~50 spheres and two light sources, measured in Mray/s.

• CPU. Testing on "PC" AMD ThreadRipper 1950X 3.4GHz (SMT disabled, 16c/16t) and "Mac" late 2013 MacBookPro 2.3GHz (4c/8t):
  • C++ w/ some SSE SIMD: PC 187, Mac 41.8
  • C++: PC 100, Mac 19.6
  • C# (Unity with Burst compiler): PC 82, Mac 18.7. Note that this is super early version of Burst.
  • C# (.NET Core): PC 53, Mac 13.1
  • C# (Mono with optimized settings): Mac 12.7
  • C# (Mono defaults): Mac 5.5
• GPU. Simple direct ports to compute shader:
  • D3D11. GeForce GTX 1080 Ti: 1854
  • Metal. Intel Iris Pro: 99

A lot of stuff in the implementation is totally suboptimal or using the tech in a "wrong" way. I know it's just a simple toy, ok :)

Building

• C++ projects: Windows (Visual Studio 2017) in Cpp/Windows/TestCpu.sln, Mac (Xcode 9) in Cpp/Mac/Test.xcodeproj.
  • Windows is DX11 Win32 app that displays result as a fullscreen CPU-updated or GPU-rendered texture.
  • Mac is a Metal app that displays result as a fullscreen CPU-updated or GPU-rendered texture.
• C# project in Cs/TestCs.sln. A command line app that renders some frames and dumps out final TGA screenshot at the end.
• Unity project in Unity. I used 2018.1 beta 12 version linked to from ECS samples.