Generate a sine wave

beginners
#1

how to generate a sine wave in a buffer and play the wave from the buffer

#2

I would:

    img.allocate(ofGetWidth(), ofGetHeight(), OF_IMAGE_COLOR);


    ofPixels& data = img.getPixels();
    int yOffset = ofGetHeight()/2;
    for(int x = 0; x < ofGetWidth(); x++){
        float sinedY = sin(x*0.05) * 20;
        float y = yOffset + sinedY;
        data.setColor(x, y, ofColor(255,255,255));
    }
    img.update();

//then
img.draw(0,0);
#3

ok but I did not mean to draw the wave, but to generate a sine wave in a buffer and play the sound from the buffer

#4

Hi!
Examples -> sounds -> audioOutputExample does something like that.
They don’t use a buffer there, but call sin() instead.
You can fill a wavetable-buffer in setup() like this:

    for(int i=0; i<BUFSIZE; i++){
        buffer[i] = sin((float)i/BUFSIZE*TWO_PI);
        cout << buffer[i] << endl;
    }

In the audioOut function you can read the data out of the wavetable-buffer to the lAudio and rAudio buffers, like this:

float freq = 200.;
float readPosIncrement = (1./(sampleRate / (BUFSIZE * freq)));

void ofApp::audioOut(float * output, int bufferSize, int nChannels){
    for (int i = 0; i < bufferSize; i++){
        readPos += readPosIncrement;
        if(readPos >= BUFSIZE)
            readPos = readPos - BUFSIZE;
        float sample = buffer[(int)readPos];
        lAudio[i] = output[i*nChannels    ] = sample * 0.5;
        rAudio[i] = output[i*nChannels + 1] = sample * 0.5;
    }
}

Something like this… Hope it gets you started!