1D linear convection

testApp.cpp

#include "testApp.h"

// generate random data for "u"
void testApp::setup(){
	ofBackground(22,33,44);
	float dt = 0.1;
	for(int i = 0; i < N; ++i) {
		u[i] = ofNoise(dt*i);
	}
}

// "propagate" the wave
void testApp::convec(float* data) {
	float dt = 0.01;
	memcpy(u_copy, u, N * sizeof(float));
	float c = 1.7; // how fast do  you want the wave to propagate
	for(int i = 1; i < N; ++i) {
		u[i] = u_copy[i] - c * dt * (u_copy[i] - u_copy[i-1]);
	}
}


// Use mouseX to change the value in u
void testApp::update(){
	ofSetWindowTitle(ofToString(ofGetFrameRate()));
	int dx = (float(mouseX) / ofGetWidth()) * N;
	dx = std::max<int>(0, std::min<int>(dx, N));
	u[dx] = mouseY * 0.01;
	convec(u);
}

void testApp::draw(){ 
	drawConvection(u);
}

void testApp::drawConvection(float* data) {
	float s = (float)ofGetWidth() / N;
	float y = 0;

	// draw as line
	glColor3f(1,1,1);
	glPointSize(2.0f);
	glBegin(GL_LINE_STRIP);
		for(int i = 0; i < N; ++i) {
			glVertex2f(i * s, y + data[i] * 100);
		}
	glEnd();
	
	// draw as points
	glColor3f(1,0,0);
	glPointSize(2.0f);
	glBegin(GL_POINTS);
		for(int i = 0; i < N; ++i) {
			glVertex2f(i * s, y + data[i] * 100);
		}
	glEnd();
}



void testApp::keyPressed(int key){}
void testApp::keyReleased(int key){}
void testApp::mouseMoved(int x, int y){ }
void testApp::mouseDragged(int x, int y, int button){}
void testApp::mousePressed(int x, int y, int button){}
void testApp::mouseReleased(int x, int y, int button){}
void testApp::windowResized(int w, int h){ }
void testApp::gotMessage(ofMessage msg){}
void testApp::dragEvent(ofDragInfo dragInfo){}

testApp.h

#pragma once

#include "ofMain.h"
#define N 64
class testApp : public ofBaseApp{
	public:
		void setup();
		void update();
		void draw();
		
		void keyPressed(int key);
		void keyReleased(int key);
		void mouseMoved(int x, int y);
		void mouseDragged(int x, int y, int button);
		void mousePressed(int x, int y, int button);
		void mouseReleased(int x, int y, int button);
		void windowResized(int w, int h);
		void dragEvent(ofDragInfo dragInfo);
		void gotMessage(ofMessage msg);

		void drawConvection(float* data);		
		void convec(float* data);
		float u[N];
		float u_copy[N];
		
};