Gui/mouse-track/render.cpp

GUI Mouse Tracker

In this project you can find a sketch.js file which is a p5.js file that is rendered in a browser tab. Click the GUI button (next to the Scope button) in the IDE to see the rendering of this file.

This example receives a buffer of data from the GUI with the X-Y coordinates of the mouse (normalised to the size of the window). The Y axis controls the pitch of an oscillator while the X axis controls L/R panning. 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', 2);

In this case we are expecting to receive a buffer of floats with a maximum of 2 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();

Additionally, two One-pole low pass filters are used to smooth the values read from the GUI and avoid glitches.

/*
 ____  _____ _        _
| __ )| ____| |      / \
|  _ \|  _| | |     / _ \
| |_) | |___| |___ / ___ \
|____/|_____|_____/_/   \_\
http://bela.io
*/
 
#include <Bela.h>
#include <libraries/Gui/Gui.h>
#include <libraries/OnePole/OnePole.h>
#include <cmath>
 
// GUI object declaration
Gui myGui;
// One Pole filter object declaration
OnePole freqFilt, ampFilt;
 
// Default frequency and panning values for the sinewave
float gFrequency = 440.0;
float gAmpL = 1.0;
float gAmpR = 1.0;
 
float gPhase;
float gInverseSampleRate;
 
bool setup(BelaContext *context, void *userData)
{
        gInverseSampleRate = 1.0 / context->audioSampleRate;
        gPhase = 0.0;
 
        // Setup GUI. By default, the Bela GUI runs on port 5555 and address 'gui'
        myGui.setup(context->projectName);
 
        // Setup buffer of floats (holding a maximum of 2 values)
        myGui.setBuffer('f', 2); // Index = 0
 
        // Setup low pass filters for smoothing frequency and amplitude
        freqFilt.setup(1, context->audioSampleRate); // Cut-off frequency = 1Hz
        ampFilt.setup(1, context->audioSampleRate); // Cut-off frequency = 1Hz
 
        return true;
}
 
void render(BelaContext *context, void *userData)
{
        for(unsigned int n = 0; n < context->audioFrames; n++) {
 
                // Get buffer 0
                DataBuffer& buffer = myGui.getDataBuffer(0);
                // Retrieve contents of the buffer as floats
                float* data = buffer.getAsFloat();
 
                // Map Y-axis (2nd element in the buffer) to a frequency range
                gFrequency = map(data[1], 0, 1, 600, 320);
                // Constrain frequency
                gFrequency = constrain(gFrequency, 320, 600);
                // Smooth frequency using low-pass filter
                gFrequency = freqFilt.process(gFrequency);
 
                // Constrain amplitude (given by the X-axis, 1st element in the buffer)
                // between 0 and 1.
                // Smooth value using low-pass filter
                float amplitude = ampFilt.process(constrain(data[0], 0, 1));
                // Calculate amplitude of left and right channels
                gAmpL = 1 - amplitude;
                gAmpR = amplitude;
 
                float out = 0.4f * sinf(gPhase);
                // Write sinewave to left and right channels
                for(unsigned int channel = 0; channel < context->audioOutChannels; channel++) {
                        if(channel == 0) {
                                audioWrite(context, n, channel, gAmpL*out);
                        } else if (channel == 1) {
                                audioWrite(context, n, channel, gAmpR*out);
                        }
                }
 
                // Update and wrap phase of sine tone
                gPhase += 2.0f * (float)M_PI * gFrequency * gInverseSampleRate;
                if(gPhase > M_PI)
                        gPhase -= 2.0f * (float)M_PI;
 
        }
 
}
 
void cleanup(BelaContext *context, void *userData)
{
 
}