Simple Acoustic Ray Tracer

A very bare-bones acoustic ray tracer that allows you to create a room and create a rough rough rough approximation of the early reverberations. This codebase depends on openFrameworks which handles the GUI portion of the ray tracer.

This is a work in progress. Over time, we hope to add better acoustics and material modelling and eventually, the ability to make 3D rooms.

Example

In this example, the following large room is modelled:

The following image shows the ray trace for a simulation time of 1 sec: Note that there are a significant number of rays escaping the room (likely due to the ray-wall collision detector unable to handle the discontinuity between two walls. This needs to be fixed).

The ray trace of the room leads to the following impulse response approximation:

Converted to the frequency domain:

The resulting impulse response can be used in a convolution reverb routine. When applied to an audio sample, the sample takes on a noticeably reverberant characteristic. There is a very grainy texture when listening directly to the impulse response which is expected since a relatively small number of rays will leave gaps between the impulse response samples.

Building the Code

First, download the latest version of openFrameworks. The easiest way to start is to create a new openFrameworks project using the project generator (openFrameworks_folder/projectGenerator), then copy the source files in this repo. You should be able to build and run the code. Note that you may need to change the window size in main.cpp.

Running

When running the application, first create a room by pressing w. Click to add corners. Hold shift while moving the mouse to create horizontal/vertical lines. When making a room, you must add corners in a clockwise fashion! The room is complete when your last corner matches the first corner (ie. You have closed the room). Tip: To close the room, hold shift and bring your mouse pointer near the first point. The mouse will automatically snap to the first point

Next, add a listener by pressing l. Click and drag it to your desired position.

Then, add an emitter by pressing e. Click and drag it to your desired position.

Finally, to start the simulation, press s. Two files, irLeft.txt and irRight.txt will be written to the path specified in the following lines in Solver.cpp:

_outputFileLeft.open("your_path_here");
_outputFileRight.open("your_path_here");

These files can be parsed to extract the IR and eventually apply it to your convolution reverb process.

TODO

• Basic operation (create world, generate rays, animate ray propgation)
• Add CMake compatibility and Unit Testing targets
• Offload ray trace operation to separate thread, draw snapshots of ray propagation at each frame change
• Add better acoustic modelling
• Add portaling and diffraction
• Add wall material properties
• Make ray reflection code more robust (handle discontinuous case between two walls)
• Apply SIMD to reflection code?
• Add better drawing of impulse response
• Add ability to make 3D world
• Add ability to communicate impulse response to other applications via OSC (or something else)
• Offload calculations to GPU?