RTIOW - Rust Version

So Far

• I first made a naive implementation of Ray Tracing In One Weekend by basically 1:1 copying the C++ into Rust
• I made changes to trade slower compilation for faster performance
  • link time optimization: fat
  • codegen units: 1
  • emit asm so llvm and further optimize
• I made various tweaks to make my code more idiomatic (hopefully), to satisfy my craving for functional programming, improve performance, and for aesthetic/dogma reasons
  • Returning options instead of mutating C-like in/out parameters and returning a bool
  • Replacing imperative loops with map to express applying an operation on the whole collection simultaneously
  • Replacing if statements with match statements for FP reasons (much flimsier justification)
• I added the rayon crate
  • Replaced .iter() and .into_iter() with .par_iter() and .into_par_iter()
  • tweaked rng generators and fold/reduce/collects until it compiled
  • Now with multithreaded execution, it was much faster

Current Steps

• Figure out how to profile execution to find what are the slow parts
  • Possibly try timing runs with glam vs my own library to see which is faster
• Figure out how to pass threadsafe rng or statically give each thread its own rng rather than making a new rng for each thing
• Figure out what the best combination of parallel iterators are
  • Rows
  • Pixel in Row
  • Photon per Pixel
  • Which of these are better parallelized accounting for thread/rng overhead
• General idiomatic code/performance improvements

Next Steps

• Ray Tracing: The Next Week
• Interactive Window
  • Move camera to find the best picture
  • Adjust camera effects like blur and fov
  • Redrawing the window takes less than 1s so low resolution and photon count
  • Load different scene
  • Fix Scene/Camera and Render high quality image to file
• Png output
• More shapes
  • Triangles, the vertex buffer default, allows for real polygons and general shapes
• More materials
• Possibly add distinction between vec3 and vec4 for homogeneous coordinates and normal vectors and such
• Allow loading of object files

Benchmarking, Profiling, and Maximizing Performance

• Increasing Performance:

  • --release vs debug
  • --emit=asm vs none
  • lto = fat vs thin vs none
  • codegen-units = 1
  • -C target-cpu=native
  • panic = abort

• Using perf to profile

$ perf record --call-graph dwarf -- cargo run --release
$ perf report

• Build

RUSTFLAGS="--emit=asm -C target-cpu=native" cargo build --release 

• Run

time target/release/./raytracer_weekend > dump.ppm