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processing - 关于扫描线和凸多边形的初学者处理问题？

问题描述

我是处理新手，我需要一些关于这个算法的帮助。我不能使用 fill() 和 line() 函数。

这应该绘制一个凸多边形（我用鼠标单击选择顶点），当我按下“T”按钮时，它将“填充（）”多边形。

int x1, y1, x2, y2;

int click;

boolean scanlineOn;



void setup() {

size(640, 480);

click = 0;

scanlineOn = false;

};



void draw() {

if (click == 2) {

beoszto(x1, y1, x2, y2);

click = 0;

x1 = -1;

y1 = -1;

x2 = -1;

y2 = -1;

};

if (scanlineOn == true) {

scanline();

scanlineOn = false;

};

};



void scanline() {

int x = 1, y = 1;

int xA = -1, yA = -1;

int xB = -1;

color a;

color b;

color c;

c = get(x, y);

while (x != 639 && y != 479) {

xA = -1;

yA = -1;

xB = -1;

while (x != 639) {

a = get(x, y);

b = get(x+1, y);

if (a != b && xA == -1) {

xA = x + 1;

yA = y;

c = get(xA, yA);

} else if (c == b && a != b) {

xB = x + 1;

};

if (xA != -1 && xB != -1){

myfill(xA, yA, xB);

xA = -1;

yA = -1;

xB = -1;

};

x = x + 1;

};

y = y + 1;

x = 1;

};

};



void myfill(int xA, int yA, int xB) {

while (xA < xB) {

point(xA, yA);

xA = xA + 1;

};

};



void beoszto(int x1, int y1, int x2, int y2) {

if (x1 < x2) {

sectiondraw(x2, y2, x1, y1);

} else if (x1 == x2 && y1 == y2) {

point(x1, y1);

} else {

sectiondraw(x1, y1, x2, y2);

};

};



void sectiondraw(int xA, int yA, int xB, int yB) {

int a, b, d, dE, dNE, a2, b2;



if (yA - yB <= 0) {

a2 = yB - yA;

} else {

a2 = yA - yB;

};

if (xA - xB <= 0) {

b2 = xB - xA;

} else {

b2 = xA - xB;

};

if (b2 >= a2) {

b = -b2;

a = a2;

} else {

b = -a2;

a = b2;

};



d = 2 * a + b;

dE = 2 * a;

dNE = 2 * (a + b);

point(xB, yB);

if (b2 >= a2 && yA >= yB) {

while (xB < xA) {

if (d >= 0) {

d = d - dE;

xB = xB + 1;

} else {

d = d - dNE;

yB = yB + 1;

xB = xB + 1;

};

point(xB, yB);

};

} else if (b2 >= a2 && yA < yB) {

while (xB < xA) {

if (d >= 0) {

d = d - dE;

xB = xB + 1;

} else {

d = d - dNE;

yB = yB - 1;

xB = xB + 1;

};

point(xB, yB);

};

} else if (b2 <= a2 && yA <= yB) {

while (yB > yA) {

if (d >= 0) {

d = d - dE;

yB = yB - 1;

} else {

d = d - dNE;

yB = yB - 1;

xB = xB + 1;

};

point(xB, yB);

};

} else {

while (yB < yA) {

if (d >= 0) {

d = d - dE;

yB = yB + 1;

} else {

d = d - dNE;

yB = yB + 1;

xB = xB + 1;

};

point(xB, yB);

};

};

};

void mousePressed() {

if (click == 0) {

x1 = mouseX;

y1 = mouseY;

click = 1;

} else {

x2 = mouseX;

y2 = mouseY;

click= 2;

};

};



void keyPressed() {

if (key == 't' || key == 'T') {

scanlineOn = true;

};

};

它是地狱般的越野车。我最大的问题是我必须用多条线绘制多边形。

标签： processing

解决方案

如果你要使用 line() 函数，你可以这样：

//Create a list of all the clicked locations
ArrayList<PVector> clicked = new ArrayList<PVector>();

void setup(){
  size(640, 480);
}


void draw(){
  if(clicked.size() > 1){
    for (int i = 1; i < clicked.size(); i++) {
      //Draw a line between each clicked point
      line(clicked.get(i).x,clicked.get(i).y,clicked.get(i-1).x,clicked.get(i-1).y);
    }
  }
}

void mousePressed(){
  //Add new mouse presses to the list
  clicked.add(new PVector(mouseX, mouseY));
}

否则不使用 line() 函数，您可以创建自己的

void newLine(float x1, float y1, float x2, float y2){
  float d = dist(x1,y1,x2,y2);
  float m1 = (y2-y1)/d;
  float m2 = (x2-x1)/d;
  for (int i = 0; i < d; i++){
    point(x1+i*m2, y1+i*m1);
  }
}

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