ray-tracing

This is a go implementation of the Ray Tracing in One Weekend book.

Motivation

After following the book in C++ and wanting to learn go, I decided to use it at my first real hands on project with go. I wanted to make the code parallel and display the progress.

Enhancements

• displays the image as it is being rendered (uses SDL)
• processes the image in multiple goroutines and multiple passes (for example, a first pass with 1 ray per pixel so that the rendering happens very quickly, and then further passes with more rays per pixel to enhance the result)
• choose the seed so that the end result is reproducible

Installation

go get -v github.com/ypujante/ray-tracing

The only dependency is on the SDL2 Binding for Go library which also requires that you install SDL for your system.

Compiling

go install

Love the simplicity...

Running

• ray-tracing will render the final scene in 800x400 pixels in 2 passes (a quick 1 ray per pixel pass and a 99 rays per pixel pass) using all the cores on your machine and a seed of 2017

• ray-tracing -r 1 -r 10 -r 50 -r 100 -w 1600 -h 800 -cpu 4 -seed 12345 will use 4 passes (1/10/50/100 rays each so a total of 161 rays per pixel) using 4 cores and a width/height of 1600x800 and a seed of 12345

Lessons learned

• rand.Float64() is (in hindsight for obvious reasons) synchronized and really killed the performances of the program since it is heavily used by each computation. Abstracted it into a Rnd interface (see model.go) and each goroutine creates its own non synchronized version to fix the issue.

• using goroutines and channels really rocks. A few very powerful set of primitives are all it takes to make asynchronous programming a joy again :).

• goroutines are fast... try -cpu 200... which will create 200 goroutines and, although you obviously do not gain by having more goroutines than the number of cores (since it is 100% CPU bound), it is pretty fascinating to also see that it is not dramatically slowing it down by having to time slice all those goroutines

• go implements interface/object orientation in a very different manner than any other language. Although it takes some time to get used to it, I really enjoyed it after a while. My Rnd interface is a good example, since I could make the rnd.Rand class magically implement it even if it is a type not defined by me.

• I do miss generics :( As far as I can tell there is no way to implement the split function I wrote in a generic fashion which is a shame.

Dependencies

• SDL2 Binding for Go

License

Apache 2.0