[work 31] Flow Field – black hole –

Movie

Source code

about

• Flow Fieldに中心方向に向かうベクトルを加える
• 中心から特定の距離に近づいたらパーティクルを削除する
• 中心に近づくほど中心方向に向かう力が強くなる

file

• 上部にあるファイル名が表示されているボタンを押すと、表示されるファイルが切り替わります
• 別ウィンドウ表示したい時や行番号などが無いRawMode表示したい時は、コード内右上のボタンを押してください（ボタンはマウスオーバーすると表示されます）

#include "ofMain.h"
#include "ofApp.h"

//================================
int main( ){

    // 4K:4096x2160
    // 2K:2048x1080
    // FullHD:1920x1080
    // HD:1440x1080
    // HD720p:1280x720
    // DVD:720x480
    // setup the GL context
	ofSetupOpenGL(1280,720, OF_WINDOW);

	// this kicks off the running of my app
	// can be OF_WINDOW or OF_FULLSCREEN
	// pass in width and height too:
	ofRunApp( new ofApp());

}

#pragma once

#include "ofMain.h"

#include "FlowField.hpp"
#include "Particle.hpp"


class ofApp : public ofBaseApp{
	public:
    ofApp();
    ~ofApp();
    
		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 mouseEntered(int x, int y);
		void mouseExited(int x, int y);
		void windowResized(int w, int h);
		void dragEvent(ofDragInfo dragInfo);
		void gotMessage(ofMessage msg);
    
private:
    std::vector<unique_ptr<Particle>> particles;
    unique_ptr<FlowField> ff;
};

#include "ofApp.h"


ofApp::ofApp(){
    
}

ofApp::~ofApp(){
    
}

//--------------------------------------------------------------
void ofApp::setup(){
    double fps = 30;
    
    ofSetFrameRate(fps);
    ofBackground(0);
    ofSetBackgroundAuto(true);
    
    ff = make_unique<FlowField>(20);
    ff->setup();
}

//--------------------------------------------------------------
void ofApp::update(){
    for (int i = 0; i < 2000; i++) {
        particles.push_back(make_unique<Particle>(ofVec2f(ofRandomWidth(), ofRandomHeight())));
    }
    
    ff->update();
    
    for (unique_ptr<Particle> &p : particles) {
        p->follow(ff);
        p->update();
    }
    ofRemove(particles, Particle::shouldRemoveOffScreen);
    ofRemove(particles, Particle::shouldRemoveInsideHole);
}

//--------------------------------------------------------------
void ofApp::draw(){
    for (unique_ptr<Particle> &p : particles) {
        p->display();
    }
}

#ifndef FlowField_hpp
#define FlowField_hpp

#include <stdio.h>
#include "ofMain.h"


class FlowField {
public:
    FlowField(int r);
    ~FlowField();
    void setup();
    void update();
    void display();
    ofVec2f lookup(ofVec2f pos);
private:
    int cols, rows;
    int resolution;
    float xoff, yoff, zoff;
    std::vector<std::vector<ofVec2f>> field;
};
#endif /* FlowField_hpp */

#include "FlowField.hpp"


FlowField::FlowField(int r)
{
    resolution = r;
    cols = ofGetWidth() / resolution;
    rows = ofGetHeight() / resolution;
    field.assign(cols, std::vector<ofVec2f>(rows, ofVec2f(0, 0)));
}


FlowField::~FlowField()
{
    
}


void FlowField::setup()
{
    zoff = 0;
}


void FlowField::update()
{
    xoff = 0;
    for (int x = 0; x < cols; x++) {
        yoff = 0;
        for (int y = 0; y < rows; y++) {
            float theta = ofMap(ofNoise(xoff, yoff, zoff), 0, 1, 0, TWO_PI);
            ofVec2f dir = ofVec2f(std::cos(theta), std::sin(theta));
            ofVec2f gravity = ofVec2f(cols/2, rows/2) - ofVec2f(x, y);
            field[x][y] = (dir.normalize() + gravity.normalize()).normalize();
            yoff += 0.05;
        }
        xoff += 0.05;
    }
    zoff += 0.01;
}


void FlowField::display()
{
    for (int x = 0; x < cols; x++) {
        for (int y = 0; y < rows; y++) {
            ofPushMatrix();
            ofTranslate(x * resolution, y * resolution);
            ofNoFill();
            ofSetColor(255);
            ofDrawRectangle(0, 0, resolution, resolution);
            
            ofVec2f c = ofVec2f(resolution / 2, resolution / 2);
            int len = resolution * 3 / 4;
            ofVec2f t0 = c - (field[x][y] * len / 2);
            ofVec2f t1 = c + (field[x][y] * len / 2);
            ofSetColor(255, 255, 0);
            ofDrawLine(t0.x, t0.y, t1.x, t1.y);
            ofPopMatrix();
        }
    }
}


ofVec2f FlowField::lookup(ofVec2f pos)
{
    ofVec2f center = ofVec2f(ofGetWidth() / 2, ofGetHeight() / 2);
    float distance;
    float power;
    if (pos != center) {
        distance = (center - pos).length();
        power = ofMap(1/distance, 0, 1/center.length(), 1, 3);
    } else {
        power = 3;
    }
    int col = (int)ofClamp(pos.x / resolution, 0, cols - 1);
    int row = (int)ofClamp(pos.y / resolution, 0, rows - 1);
    return field[col][row] * power;
}

#ifndef Particle_hpp
#define Particle_hpp

#include <stdio.h>
#include "ofMain.h"
#include "FlowField.hpp"


class Particle {
public:
    Particle(ofVec2f l);
    ~Particle();
    void update();
    void display();
    
    void follow(unique_ptr<FlowField> &flow);
    void applyForce(ofVec2f force);
    
    static bool shouldRemoveOffScreen(unique_ptr<Particle> &p);
    static bool shouldRemoveInsideHole(unique_ptr<Particle> &p);
private:
    ofVec2f getLocation();
    void setVelocity();
    
    ofColor color;
    ofVec2f location;
    ofVec2f velocity;
    ofVec2f acceleration;
    float radius;
    float maxforce;
    float maxspeed;
    float tx;
};
#endif /* Particle_hpp */

#include "Particle.hpp"


bool Particle::shouldRemoveOffScreen(unique_ptr<Particle> &p)
{
    return !ofRectangle(0, 0, ofGetWidth(), ofGetHeight()).inside(p->getLocation());
}

bool Particle::shouldRemoveInsideHole(unique_ptr<Particle> &p)
{
    bool ret = false;
    ofVec2f center = ofVec2f(ofGetWidth() / 2, ofGetHeight() / 2);
    float radius = 80;
    float distance = (center - p->getLocation()).length();
    
    if (distance < radius + ofRandom(-15, 15)) {
        ret = true;
    }
    
    return ret;
}

Particle::Particle(ofVec2f l)
{
    ofColor c;
    c.setHsb(ofRandom(0, 30), ofRandom(0, 255), ofRandom(128, 255));
    color = c;
    maxspeed = 3;
    maxforce = 0.3;
    acceleration = ofVec2f(0, 0);
    velocity = ofVec2f(0, 0);
    location = l;
    radius = 1;
    tx = 0;
}


Particle::~Particle()
{
    
}


void Particle::update()
{
    location += velocity;
    acceleration *= 0;
}


void Particle::display()
{
    ofPushMatrix();
    ofFill();
    ofSetColor(color);
    ofTranslate(location.x, location.y);
    ofDrawCircle(0, 0, radius);
    ofPopMatrix();
}


void Particle::follow(unique_ptr<FlowField> &flow)
{
    ofVec2f desired = flow->lookup(location);
    desired *= maxspeed;
    
    ofVec2f steer = desired - velocity;
    steer.limit(maxforce);
    applyForce(steer);
}


void Particle::applyForce(ofVec2f force)
{
    acceleration += force;
    setVelocity();
}


ofVec2f Particle::getLocation()
{
    return location;
}


void Particle::setVelocity()
{
    velocity += acceleration;
    velocity.limit(maxspeed);
}

Link to the reference page

ソースコードで使用したAPIの中から要点になりそうなものをいくつか選んでリストアップしました。

Development environment

• openframeworks 0.10.1
• c++
• macOS
• Xcode