Gui/gui-to-bela/render.cpp

Sending from the GUI to Bela

This project is a minimal example on how to send data buffers from p5js to Bela. Bela (render.cpp) receives a buffer of data from p5js (sketch.js) containing three floats: two corresponding to slider values and the third one correponding to a button. These values are then mapped as parameters of an oscillator object. The mapping is: slider1-->pitch slider2-->amplitude button-->play/stop

HOW TO RECEIVE A BUFFER IN BELA

In order to receive a buffer from the GUI, the type of the buffer and maximum number of values that it will hold need to be specified in setup:

myGUi.setBuffer('f', 3);

In this case we are expecting to receive a buffer of floats with a maximum of 3 elements. This function will return the index of the buffer (which is given automatically based on the order they are set on). This buffer will have index = 0. The buffer can then be accessed using this index:

DataBuffer& buffer = myGui.getDataBuffer(0);

Notice that the Gui::getDataBuffer() method returns a DataBuffer& (that is: a reference to a DataBuffer). You should in turn always be storing the return value in a DataBuffer& variable to minimize copy overhead, and ensure that it can be used safely from within a real-time context.

And its contents retrieved in the desired format (floats in this case): float* data = buffer.getAsFloat();

/*
 ____  _____ _        _
| __ )| ____| |      / \
|  _ \|  _| | |     / _ \
| |_) | |___| |___ / ___ \
|____/|_____|_____/_/   \_\
http://bela.io
*/
#include <Bela.h>
#include <libraries/Oscillator/Oscillator.h>
#include <libraries/Gui/Gui.h>
#include <cmath>
 
//create a gui and an oscillator object
Gui gui;
Oscillator oscillator;
 
 
 
bool setup(BelaContext *context, void *userData)
{
        // Set up oscillator and GUI
        oscillator.setup(context->audioSampleRate);
        gui.setup(context->projectName);
 
        //Set the buffer to receive from the GUI
        gui.setBuffer('f', 3);
        return true;
}
 
void render(BelaContext *context, void *userData)
{
        //We store the DataBuffer in 'buffer'
        DataBuffer& buffer = gui.getDataBuffer(0);
        // Retrieve contents of the buffer as floats
        float* data = buffer.getAsFloat();
 
        //store each element of the array in local variables
        float pitch = data[0]; //range of values is [0,1],
        pitch = map(pitch,0,1,40,80); // we map it to [20,80] for MIDI pitches
        float amplitude = data[1]; //range is [0,1]
        float play = data[2]; //0.0 or 1.0
 
        //for mapping
        float frequency = 440 * powf(2, (pitch-69)/12); // compute the frequency based on the MIDI pitch
        oscillator.setFrequency(frequency);
        // notice: no smoothing for amplitude and frequency, you will get clicks when the values change
 
        for(unsigned int n = 0; n < context->audioFrames; n++) {
                float out = oscillator.process() * amplitude * play;
                for(unsigned int channel = 0; channel < context->audioOutChannels; channel++) {
                        // Write the sample to every audio output channel
                        audioWrite(context, n, channel, out);
                }
        }
}
 
void cleanup(BelaContext *context, void *userData)
{}