Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit


Git stats


Failed to load latest commit information.
Latest commit message
Commit time

CMake Ray Tracer

A simple ray tracer written in pure CMake. Inspired by raytracer.hpp. More information can be found at my blog.



The ray tracer writes its output to stderr, so you can use it with:

cmake -Dimage_width=64 -Dimage_height=64 -Dnum_procs=4 -P CMakeLists.txt 2> image.ppm

Which writes the output to image.ppm. Then use an image viewer capable of opening PPM files (or this) to view.

Alternatively, the ray tracer can directly write PNG files courtesy of @benmcmorran (PowerShell required for now). Use the use_png variable to set the name of the PNG file without the extension. The example below will write output to render.png.

cmake -Dimage_width=64 -Dimage_height=64 -Dnum_procs=4 -Duse_png=render -P CMakeLists.txt

num_procs controls the number of worker processes spawned. It is recommended to set this to a value no greater than the number of cores in your CPU, for maximum performance.

For now, to keep the code simple, you are required to keep image_width, image_height and num_procs as powers of 2, otherwise the image may not be fully formed. If not specified, these arguments default to the values shown above.


Using cmake 3.19.2 on Linux 5.4 on a i5-10210U (4 cores, 8 threads), running this command:

for X in 1 2 4 8 16 32 64 128 256 512 ; do echo SIZE $X ; time cmake -Dimage_width=$X -Dimage_height=$X -Dnum_procs=8 -P CMakeLists.txt 2> image_size_${X}.ppm  ; done

PowerShell alternative:

1, 2, 4, 8, 16, 32, 64, 128, 256, 512 | foreach {Write-Host $_; (Measure-Command { cmake "-Dimage_width=$_" "-Dimage_height=$_" "-Dnum_procs=$Env:NUMBER_OF_PROCESSORS" -P CMakeLists.txt 2> image_size_$_.ppm }).TotalSeconds}

Figures reported by time command below (reformatted). As usual, the "real" time is the wall clock time. The others are summed on all processors.

size real user sys
1 0,054s 0,130s 0,051s
2 0,035s 0,098s 0,041s
4 0,077s 0,274s 0,018s
8 0,106s 0,460s 0,023s
16 0,367s 1,871s 0,059s
32 1,296s 7,617s 0,132s
64 5,175s 29,455s 0,356s
128 21,093s 2m06,299s 1,566s
256 1m33,395s 9m21,875s 5,999s
512 7m23,094s 45m36,327s 32,588s


All contributions (issue, PRs) are welcome. This project is licensed under the MIT license.


Ray tracer written in pure CMake