annotate projects/airharp/render.cpp @ 269:ac8eb07afcf5

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/*
 * AIR-HARP
 * Physically modelled strings using waveguide junctions and mass-spring-dampers
 *
 * render.cpp
 *
 * Christian Heinrichs 04/2015
 *
 */


#include "MassSpringDamper.h"
#include "String.h"
#include "Plectrum.h"

#include <BeagleRT.h>
#include <cmath>
#include <stdio.h>
#include <cstdlib>
#include <rtdk.h>
#include "../include/Utilities.h"

#define ACCEL_BUF_SIZE 8
#define NUMBER_OF_STRINGS 9

// PENTATONIC SCALE
float gMidinotes[NUMBER_OF_STRINGS] = {40,45,50,55,57,60,62,64,67};

float gInverseSampleRate;

float out_gain = 5.0;

int accelPin_x = 0;
int accelPin_y = 1;
int accelPin_z = 2;

MassSpringDamper msd = MassSpringDamper(1,0.1,10);// (10,0.001,10);
String strings[NUMBER_OF_STRINGS];
Plectrum plectrums[NUMBER_OF_STRINGS];

float gPlectrumDisplacement = 0;

float gAccel_x[ACCEL_BUF_SIZE] = {0};
int gAccelReadPtr = 0;

// DC BLOCK BUTTERWORTH

// Coefficients for 100hz cut-off
float a0_l = 0.9899759179893742;
float a1_l = -1.9799518359787485;
float a2_l = 0.9899759179893742;
float a3_l = -1.979851353142371;
float a4_l = 0.9800523188151258;

float a0_r = a0_l;
float a1_r = a1_l;
float a2_r = a2_l;
float a3_r = a3_l;
float a4_r = a4_l;

float x1_l = 0;
float x2_l = 0;
float y1_l = 0;
float y2_l = 0;

float x1_r = 0;
float x2_r = 0;
float y1_r = 0;
float y2_r = 0;


bool setup(BeagleRTContext *context, void *userData)
{

	gInverseSampleRate = 1.0 / context->audioSampleRate;

	// initialise strings & plectrums
	for(int i=0;i<NUMBER_OF_STRINGS;i++)	{

		plectrums[i] = Plectrum();
		plectrums[i].setup(250,0.25,0.05);

		strings[i] = String();
		strings[i].setMidinote(gMidinotes[i]);

		float spacing = 2.0 / (NUMBER_OF_STRINGS+1);

		strings[i].setGlobalPosition( -1 + spacing*(i+1) );

		rt_printf("STRING %d // midinote: %f position: %f\n",i,gMidinotes[i],( -1 + spacing*(i+1) ));

	}

	return true;
}

void render(BeagleRTContext *context, void *userData)
{

	float lastAccel = 0;

	for(int n = 0; n < context->audioFrames; n++) {

		/*
		 *
		 * ACCELEROMETER DATA
		 *
		 */

		// Read accelerometer data from analog input
		float accel_x = 0;
		if(n%2)	{
			accel_x = (float)context->analogIn[(n/2)*8+accelPin_x] * 2 - 1;	// 15800 - 28300 - 41500
			lastAccel = accel_x;
		} else {
			// grab previous value if !n%2
			accel_x = lastAccel;
		}

		// Dead-zone avoids noise when box is lying horizontally on a surface

		float accelDeadZone = 0.1;

		if(accel_x <= accelDeadZone && accel_x >= -accelDeadZone)
			accel_x = 0;

		// Perform smoothing (moving average) on acceleration value
		if(++gAccelReadPtr >= ACCEL_BUF_SIZE)
			gAccelReadPtr = 0;
		gAccel_x[gAccelReadPtr] = accel_x;
		float gravity = 0;
		for(int i=0;i<ACCEL_BUF_SIZE;i++)	{
			gravity = gAccel_x[(gAccelReadPtr-i+ACCEL_BUF_SIZE)%ACCEL_BUF_SIZE];
		}
		gravity /= ACCEL_BUF_SIZE;

		/*
		 *
		 * PHYSICS SIMULATION
		 *
		 */

		// The horizontal force (which can be gravity if box is tipped on its side)
		// is used as the input to a Mass-Spring-Damper model
		// Plectrum displacement (i.e. when interacting with string) is included
		float massPosition = (float)msd.update(gravity - gPlectrumDisplacement);

		float out_l = 0;
		float out_r = 0;
		// Use this parameter to quickly adjust output gain
		float gain = 0.0015;	// 0.0015 is a good value or 12 strings
		gPlectrumDisplacement = 0;

		for(int s=0;s<NUMBER_OF_STRINGS;s++)	{

			float stringPosition = strings[s].getGlobalPosition();

			float plectrumForce = plectrums[s].update(massPosition, stringPosition);
			gPlectrumDisplacement += strings[s].getPlectrumDisplacement();

			// calculate panning based on string position (-1->left / 1->right)
			float panRight = map(stringPosition,1,-1,0.1,1);
			float panLeft = map(stringPosition,-1,1,0.1,1);
			panRight *= panRight;
			panLeft *= panLeft;

			float out = strings[s].update(plectrumForce)*gain;

			out_l += out*panLeft;
			out_r += out*panRight;

		}

		// APPLY DC-BLOCK FILTER TO OUTPUTS

		// LEFT CHANNEL
		float temp_in = out_l;
		/* compute result */
    	out_l = a0_l * out_l + a1_l * x1_l + a2_l * x2_l - a3_l * y1_l - a4_l * y2_l;
    	/* shift x1 to x2, sample to x1 */
    	x2_l = x1_l;
    	x1_l = temp_in;
    	/* shift y1 to y2, result to y1 */
    	y2_l = y1_l;
   	 	y1_l = out_l;

   	 	// RIGHT CHANNEL
		temp_in = out_r;
		/* compute result */
    	out_r = a0_r * out_r + a1_r * x1_r + a2_r * x2_r - a3_r * y1_r - a4_r * y2_r;
    	/* shift x1 to x2, sample to x1 */
    	x2_r = x1_r;
    	x1_r = temp_in;
    	/* shift y1 to y2, result to y1 */
    	y2_r = y1_r;
   	 	y1_r = out_r;

		context->audioOut[n * context->audioChannels + 1] = out_l * out_gain;
		context->audioOut[n * context->audioChannels + 0] = out_r * out_gain;

	}

}


// cleanup_render() is called once at the end, after the audio has stopped.
// Release any resources that were allocated in initialise_render().

void cleanup(BeagleRTContext *context, void *userData)
{

}