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PartialString – A finite-difference time-domain physical modelling synthesiser

differentinstruments.com

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Re: PartialString – A finite-difference time-domain physical modelling synthesiser

#4

Post by IsTom »

amelius wrote: post #2

This simulates the displacement of the string, but the hard part seems to be to simulate how that string affects the air and induces a sound.

Considering that there's a pickup in the model, air doesn't matter. And in typical string instruments the loud part you mostly hear is coming from sound box through bridge, not from strings themselves.

Re: PartialString – A finite-difference time-domain physical modelling synthesiser

#5

Post by gsliepen »

The simplest form of string synthesis is perhaps the Karplus-Strong algorithm (https://en.wikipedia.org/wiki/Karplus%E2%80%93Strong_string_...). Instead of simulating the motion of all parts of the string for each timestep, it simplifies it to a perfect transmission of motion, except at the end of the string where some function will be applied that captures the losses from the motion, typically by performing a simple low-pass filter. Computationally it is very efficient: just a few FMA operations per sample. The drawback is that you need a buffer to store the state of the string, which can be quite large (especially for low frequencies which correspond to long strings), and you need to read and write to different parts of this buffer. Thus, if you are simulating multiple strings, it's more likely that memory bandwidth will be the bottleneck instead of raw compute power.

Re: PartialString – A finite-difference time-domain physical modelling synthesiser

#6

Post by DennisP »

gsliepen wrote: post #5

The simplest form of string synthesis is perhaps the Karplus-Strong algorithm ( https://en.wikipedia.org/wiki/Karplus%E2%80%93Strong_string_... ). Instead of simulating the motion of all parts of the string for each timestep, it simplifies it to a perfect transmission of motion, except at the end of the string where some function will be applied that captures the losses from the motion, typically by performing a simp…

So doing it on a big GPU would be pretty helpful. I wonder if anyone has used CUDA for this, or if any hardware synths have GPUs.

Re: PartialString – A finite-difference time-domain physical modelling synthesiser

#7

Post by Blackthorn »

DennisP wrote: post #6
gsliepen wrote: post #5

The simplest form of string synthesis is perhaps the Karplus-Strong algorithm ( https://en.wikipedia.org/wiki/Karplus%E2%80%93Strong_string_... ). Instead of simulating the motion of all parts of the string for each timestep, it simplifies it to a perfect transmission of motion, except at the end of the string where some function will be applied that captures the losses from the motion, typically by performing a simp…

So doing it on a big GPU would be pretty helpful. I wonder if anyone has used CUDA for this, or if any hardware synths have GPUs.

The time it takes to get data to/from the GPU is problematic given the sample rate you need to deliver.

Anukari used the GPU but eventually abandoned it for the CPU. They have some good and informative blog posts about it.

Re: PartialString – A finite-difference time-domain physical modelling synthesiser

#8

Post by blovescoffee »

IsTom wrote: post #3

Does it take nonlinearity of strings into account? In the demo I can't really hear it and to me it ends up sounding like the comb filter synths you get without it.

I’m super curious what that would sound like. Could you elaborate on the non linearity part?
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