Ray Tracing

This project is based on https://raytracing.github.io/ and includes some additional twists like curved space.

Note: For a conventional linear ray tracer see commit b6bbcfe.

Features

Adaptive Non-Linear Ray Propagation

Created with build/examples/basic_swirl (version ee5499f) using swirl_strength = 0.01 and resolution_factor = 4.

Created with build/examples/basic_twisted_orb (version f952428) using twist_angle = -6.0, resolution_factor = 4, ray_error_abs = 1e-12 and ray_depth = 10000.

Created with build/examples/schwarzschild (version e931515) using speed_of_light = 100.0, schwarzschild_radius = 1.0, resolution_factor = 4, ray_error_abs = 1e-8 and ray_depth = 75. Took 303min12sec user time (intel i5-4590).

N-Dimensional Manifolds

Minkowski Space

https://user-images.githubusercontent.com/7516208/204099110-1542b566-2150-459e-9823-26b5d7b94740.mp4

Conventional 3D raytracing with infinite speed of light (for reference). The 3D spheres grow and shrink over time. All textures are time-independent. Everything appears to be synchronized. Created with build/examples/basic_minkowski (version 9693243b).

https://user-images.githubusercontent.com/7516208/204099119-b7f8173d-471f-46bd-bddc-3b9e0f70dbe6.mp4

4D raytracing in Minkowski space with a finite speed_of_light=7.0. Shown are 4D spheres (glomes) which appear to change size over time. All textures are 4D time-dependent chess board patterns and change color for every unit of space or time. The finite speed reults in distant events appearing to be delayed. Created with build/examples/basic_minkowski (version 9693243b).

https://user-images.githubusercontent.com/7516208/203775340-f9e0c10b-fd77-4084-9130-7be2bd69b9e7.mp4

Same setup as before but for varying speed_of_light (0 to 20) for a fixed moment in time. The faster the speed of light, the shorter the aparrent delay between two spatial regions. Created with build/examples/basic_minkowski (version 27d8af63).

Materials

Diffuse, Dielectric, Metal & Emission

Rolling Shutter & Motion Blur

Wheel in Motion.

Resting.

Optimizations

• Multi-Threaded
  • Rendering (fully)
  • BVH Tree Generation (partially)
• Bounding Volume Hierachy (BVH)

Performance

geometry	curved	curved	flat
method	adaptive Cash-Karp	adaptive Cash-Karp	adaptive Cash-Karp
file (commit f229e20)	examples/basic_twisted_orb	examples/basic_twisted_orb	examples/basic_twisted_orb
size (resolution_factor)	480x270 pixel (2)	480x270 pixel (2)	480x270 pixel (2)
samples	100	100	100
twist_angle	-6.0	-3.0	0.0
ray_error_abs	1e-10	1e-10	1e-3
user time (intel i5-4590)	61min31sec	47min17sec	2min41sec

geometry	curved	flat	flat
method	adaptive Cash-Karp	adaptive Cash-Karp	linear
file (commit 2cc272e)	examples/basic_swirl	examples/basic_swirl	examples/basic_euclidean
size (resolution_factor)	480x270 pixel (2)	480x270 pixel (2)	480x270 pixel (2)
samples	100	100	100
swirl_strength	0.01	0.0	-
ray_error_abs	1e-10	1e-10	-
user time (intel i5-4590)	30min11sec	5min47sec	9sec

note: The image in the middle and right are identical due to the strong similarity of the renderers and usage of pseudo-random number generators with fixed seeds.

Build, Test & Preview

make

See ./build for the executables and ./out directory for the test image output.

Documentation

make doc

See ./doc directory for the documentation.

Run

./build/examples/<executable>

Where <executable> is any of the provided executables. Use --help to see the respective usage.

Image File Formats & Processing

The current image formats focus on ease on implementation and depend on netpbm.

• PPM (Protable PixelMap also known as PNM) dircrete netpbm format (similar to PNG, JPEG etc.)
• PFM (Protable FloatMap) floating point netpbm format (similar to HDR, RAW etc.)

To convert to the desired formats via the netpbm package. E.g.

pnmtopng $file.pnm > $file.png
pfmtopam $file.pfm > $file.pam
pamtopng $file.pam > $file.PNG
# ...

Or use imagemagick. E.g.

magick $file.pfm -gamma 1.0 -set gamma 1.0 $file.png
magick $file.pfm -gamma 1.0 -set gamma 1.0 $file.tiff

Proper exposure and color grading can be archived the same way as for images taken by real cameras. E.g. with darktable.

Build Documentation

make doc

See doc/html/index.html for the documentation.

Auto-Format

Run

.auto_format

to automatically format the entire code base (requires clang-format).

Debug

Add DEBUG=1 to make. The executables will be placed in build/debug instead.

Profile

Run

./profile

to get a profile (requires valgrind (profiler) and kcachegrind (show data)).

Requirements

• Linux kernel v6.3+
• C++20
• C++ Boost v1.80+
• gcc v13.1+ or glang v15.0+
• make v4.4+
• doxygen v1.9+ (optional, documentation)
• netpbm v10.73+ (optional, image processing)
• imagemagick v7.1+ (optional, image processing)
• darktable v3.8+ (optional, image processing)
• ffmpeg v6.0+ (optional, video processing)
• clang-format v15.0+ (optional, development)
• clang-tidy v15.0+ (optional, development)
• valgrind v3.21+ (optional, debug & profiling)
• kcachegrind v23.04+ (optional. debug & profiling)

General Remarks

• The heavy usage of headers is intended for future use of c++ modules. Unfortunately, c++ modules are currently (Sep 2022) not widespread enough to be considered supported by all compilers.

Movies

Curved

https://user-images.githubusercontent.com/7516208/191520786-c169b980-c4e6-4899-bd09-c5c95d53e7d6.mp4

Flat

https://user-images.githubusercontent.com/7516208/191520742-2c9fdb1e-5f0b-4696-b266-64c635c4e64b.mp4