Scrape Audio System - Behind the Scenes

This video shows a look behind the curtain of the scrape audio system for BeamNG.drive - from recording, over editing, to implementation and game context.

For the recording process, I gathered some old car parts from a garage near our office and several surface types from a hardware shop. By scraping each vehicle part against each surface, I could capture a large amount of different scrape types. Essentially, those were:

- Metal vs. Asphalt, Gravel, Dirt, Sand
- Plastic vs. Asphalt, Gravel, Dirt, Sand

The sound character was also dependent on the actual vehicle part that was scraped against the surface: Although both made out of metal, a muffler scraped against asphalt sounded very different from a wheel rim scraped against asphalt.

For the recordings, I used two cardioid condenser microhpones (Sennheiser MKH 8040), each at a different distance, and a contact microhpone (Barcus Berry 4000 Planar System), which captures physical vibrations, rather than sonic waves. The final assets were mostly a mix of one of the condenser microphones and the contact microphone, rendered as a single mono loop.

To make sure I had enough material to create a smooth sounding loop, I recorded several minutes of each object-surface combination. The loops were then cleaned up from unwanted noise and I applied some subtle EQ, limiting and compression. I ended up with a huge scrape sound library, with 252 assets that I could try out. Of course, what ultimately ended up in-game is just a fraction of that, but as is often the case with audio design, it was a lot about experimentation and trying out different approaches.

The sound for vegetation collision was actually a side-product of the scrape system. At some point, one of our programmers pointed out to me, that the scrapes are also triggered by collision with bushes and trees. Initially, it was just the "default" metal/plastic vs. asphalt scrapes, which didn´t even sound too bad. But we thought we could do better and designed a more appropriate vegetation scrape sound: A combination of the base metal/plastic scrapes with some EQ and additional "sweeteners" that were created from rustling bush, tree and wood recordings.

Also the implementation part was very much a process of trial and error. Equally important to the scrape audio assets and FMOD setup (our audio middleware) was of course the underlying physics and code driving the sounds. The dials I turn in the implementation part of the video are so called "RTPCs" or "Real-Time-Parameter-Controls": Audio parameters that change the sound based on game input. For the scrape system, those are the physics parameters that are sent to FMOD:

"Volume" = velocity * energy: controls volume
"Pitch" = velocity: controls pitch and EQ settings
"Color" = load: controls volume, pitch and EQ settings
"Texture" = looseness (surface type): triggers additional "sweeteners" on top of the base scrape sound.

So if you play BeamNG.drive, you will notice that the sound character of the scrapes will change depending on what you do: The size and material of the scraping object, surface type, scrape force, speed, distance and environment (e.g. in a tunnel or open field) are all modulating the scrape sound in real-time.

As with all audio features - the scrape system is still work-in-progess, so please do not consider the current state to be final. As we move on with development, we will further improve the scrape sounds, fix issues if we find them and possibly extend the scrape audio sysetem to support new features like scrapes against mud, water or metal.

Until then - happy scraping!

 

As we're on the topic of audio samples...
Have you ever thought about recording a sound of a single diesel injector firing, so you could then use it as an overlay for an existing gasoline sounds with correction on the amount of cylinders?

 

A making-of of the engine and exhaust sound synthesis is a nice idea, though it would probably be less boring that in sounds like. We do not record our own vehicle samples (yet) and the implementation is rather technical and less creative compared to the scrapes. But as the scrape making-of was perceived pretty well, we will consider making more of these in the future about other topics.

 

That sounds like a nice idea in theory, but I´m not sure if that would work in practice. It would be an interesting experiment though. Until now, we have not done any engine sound recordings ourselves, but rely on a third party to provide us with engine samples. We might consider recording our own engine sounds in the future.

 

Yes, that´s how it is supposed to work. In the first gameplay clip of above video, you can see me scraping the whole van across asphalt, and then just single parts of that vehicle. Responsible for the difference in sound character is mostly the "color" RTPC. So the bigger parts have more weight and thus increase the volume of one of the scrape layers that contains a lot of low frequencies, giving the overall scrape more "body". Also, with increasing speed, the scrape sound becomes louder, increases slightly in pitch, and gets filtered with an EQ dynamically (pronouncing the high frequencies). None of that happens in a linear fashion, but with the help of custom created automation curves that map each physics input value to an output value causing a change in sound. These are the automation curves for the "pitch" RTPC: