Overview:
Here is just a brief record of some implementation ideas. This part of the code does not have the actual use function.
Consider using 4 knives to cut a figure each. The core idea is that there is a point that scans the boundary of the entire graph. During the scanning process, if it goes from the inside of the knife (you need to define it yourself) to the outside of the knife, then record the current point p0. When entering the internal measurement from the outside again, connect the current point and the recorded p0. For the boundary of "covering occlusion",
(a^b)^b = a can be used to achieve "erase restoration".
#include <GLUT/GLUT.h>
#include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;
float wid = 400; //设置窗口的大小,约定窗口必须为正方形
float height = wid; //设置窗口的大小
int numbers = 40; //设置划分的网格的个数
float t = wid/numbers; //模拟像素下的单位1
int index_y; //记录下斜率为-1时的y的位置
int con[801][801]; //相当于我们的画布（其中的信息是有层次的）
int visited[801][801];
int flag = 0; //标定移动轨迹的位置
int x_pos,y_pos,x_1=2*wid,y_1=2*wid;
int pixel_size = 8; //统一设定所有的的pixel的大小；
/*
参数设置说明：
您应当确保参数范围在-400～400.且为整数。
由于使用的是模拟像素，应保持数据为单位模拟像素值的倍数。
*/
int x=0;
int y=0;
int a = 300;
int b = 200;
void draw_point(float x, float y,float x1,float y1);
void add(int x, int y ,int data){
con[x+400][y+400] = data ;
}
float translater(int x){
/*
函数说明：将像素坐标下的坐标转化为openGL坐标
参数说明：传入点像素坐标-wid-wid，返回-1～1坐标
*/
return x/wid;
}
void draw_point(float x , float y){
/*
函数说明：绘制像素的点，这里将点的大小设置为7。
颜色采用蓝色。利用圆八个部分的坐标对应关系进行绘图。
加x1与y1是为了进行圆的平移
参数说明：浮点数x，y是openGl坐标系。
*/
glPointSize(pixel_size);
glColor3f(1.0,0.0,0.0);
glBegin(GL_POINTS);
glVertex3f(x,y,0.0);
glVertex3f(-x,y,0.0); //关于y轴对称
glVertex3f(x,-y,0.0); //关于x轴对称
glVertex3f(-x,-y,0.0); //关于原点对称
glEnd();
glFlush();
}
bool out_of_index(int x,int y){
if(y>=801||x>=801||x<0||y<0){
return 0;
}else{
return 1;
}
}
void draw_inner(int x, int y){
glPointSize(pixel_size);
glColor3f(0.0,1.0,1.0);
glBegin(GL_POINTS);
glVertex3f(translater(x-400),translater(y-400),0.0);
glEnd();
glFlush();
}
void draw_inner2(int x, int y){
glPointSize(pixel_size);
glColor3f(0.0,0.0,1.0);
glBegin(GL_POINTS);
glVertex3f(translater(x-400),translater(y-400),0.0);
glEnd();
glFlush();
}
void draw_line(int x,int y , int xx , int yy){
for (int i = min(x,xx); i <= max(x,xx); i+=10) {
for(int j =min (y,yy);j<=max(y,yy);j+=10){
if(con[i][j]!=1){
int res= con[i][j]^1111;
if(res == -1){
glPointSize(pixel_size);
glColor3f(1.0,0.0,0.0);
glBegin(GL_POINTS);
glVertex3f(translater(i-400),translater(j-400),0.0);
glEnd();
glFlush();
}else{
draw_inner(i, j);
}
if(con[i][j] ==0){
con[i][j] = 1;
visited[i][j] =1;
}else{
con[i][j] = res;
}
}
}
}
}
void draw_line2(int x,int y , int xx , int yy){
for (int i = min(x,xx); i <= max(x,xx); i+=10) {
for(int j =min (y,yy);j<=max(y,yy);j+=10){
if(con[i][j]!=1){
int res= con[i][j]^1112;
if(res == -1&&res== ((-1)^1111)){
glPointSize(pixel_size);
glColor3f(1.0,0.0,0.0);
glBegin(GL_POINTS);
glVertex3f(translater(i-400),translater(j-400),0.0);
glEnd();
glFlush();
}else{
draw_inner2(i, j);
}
con[i][j] = res;
}
}
}
}
void search(int x,int y,int index){
cout << index << " - - "<<endl;
/*
函数说明：进行Dfs搜索并模拟四把刀当中的其中一把刀
可视化着色采用淡蓝色。
参数说明：x y是坐标，index是指明哪一把刀。
传入的xy是数组坐标！
*/
if (visited[x][y] ==1) {
return;
}
if(index == 1){
//讨论下方的情况
if(flag ==0){
//如果本来在外侧
if(y-400 >= -200){
//从外侧进入内侧
draw_inner(x, y);
y_1 = min(y_1,y);
x_1 = min(x_1,x);
flag =1;
x_pos= x;
y_pos = y;
}else{
glPointSize(8);
glColor3f(0.5,0.5,0.5);
glBegin(GL_POINTS);
glVertex3f(translater(x-400),translater(y-400),0.0);
glEnd();
glFlush();
flag =0;
con[x][y] = 0;
}
}else if(flag==1){
//如果本来在内侧进入了外侧
if(y-400 <= -200){
draw_inner(x, y);
//从内侧进入外侧
draw_line(x_pos, y_pos, x, y);
x_pos = 0;
y_pos =0;
flag =0;
}else{
flag=1;
draw_inner(x, y);
y_1 = min(y_1,y);
x_1 = min(x_1,x);
}
}
visited[x][y] = 1;
if(out_of_index(x+10, y)&&con[x+10][y]==1&&visited[x+10][y]==0){
search(x+10,y,index);
visited[x+10][y] =1;
}
if(out_of_index(x,y+10)&&con[x][y+10]==1&&visited[x][y+10]==0){
search(x,y+10,index);
visited[x][y+10] =1;
}
if(out_of_index(x+10,y+10)&&con[x+10][y+10]==1&&visited[x+10][y+10]==0){
search(x+10,y+10,index);
visited[x+10][y+10] =1;
}
if(out_of_index(x+10,y-10)&&con[x+10][y-10]==1&&visited[x+10][y-10]==0){
search(x+10,y-10,index);
visited[x+10][y-10] =1;
}
if(out_of_index(x,y-10)&&con[x][y-10]==1&&visited[x][y-10]==0){
search(x,y-10,index);
visited[x][y-10] =1;
}
if(out_of_index(x-10,y)&&con[x-10][y]==1&&visited[x-10][y]==0){
search(x-10,y,index);
visited[x-10][y] =1;
}
if(out_of_index(x-10,y+10)&&con[x-10][y+10]==1&&visited[x-10][y+10]==0){
search(x-10,y+10,index);
visited[x-10][y+10] =1;
}
if(out_of_index(x-10,y-10)&&con[x-10][y-10]==1&&visited[x-10][y-10]==0){
search(x-10,y-10,index);
visited[x-10][y-10] =1;
}
}else if(index ==2){
//讨论左侧的情况
if(flag ==0){
//如果本来在外侧
if(x-400 >= -300){
draw_inner2(x, y);
//从外侧进入内侧
flag =1;
x_pos= x;
y_pos = y;
}else{
glPointSize(8);
glColor3f(1.0,1.0,1.0);
glBegin(GL_POINTS);
glVertex3f(translater(x-400),translater(y-400),0.0);
glEnd();
glFlush();
flag =0;
}
}else if(flag==1){
//如果本来在内侧进入了外侧
if(x-400 <= -300){
draw_inner2(x, y);
//从内侧进入外侧
cout << "inner -> outer "<< endl;
cout << x_pos <<" == "<< y_pos <<endl;
cout << x <<" === " << y <<endl;
draw_line2(x_pos, y_pos, x, y);
cout << con[x-10][y] <<"here !! "<< endl;
x_pos = 0;
y_pos =0;
flag =0;
}else{
flag=1;
draw_inner2(x, y);
}
}
visited[x][y] = 1;
if(out_of_index(x+10, y)&&(con[x+10][y]==1||con[x+10][y]==(-1^1111))&&visited[x+10][y]==0){
search(x+10,y,index);
visited[x+10][y] =1;
}
if(out_of_index(x,y+10)&&(con[x][y+10]==1||con[x][y+10]==(-1^1111))&&visited[x][y+10]==0){
search(x,y+10,index);
visited[x][y+10] =1;
}
if(out_of_index(x+10,y+10)&&(con[x+10][y+10]==1||con[x+10][y+10]==(-1^1111))&&visited[x+10][y+10]==0){
search(x+10,y+10,index);
visited[x+10][y+10] =1;
}
if(out_of_index(x+10,y-10)&&(con[x+10][y-10]==1||con[x+10][y-10]==(-1^1111))&&visited[x+10][y-10]==0){
search(x+10,y-10,index);
visited[x+10][y-10] =1;
}
if(out_of_index(x,y-10)&&(con[x][y-10]==1||con[x][y-10]==(-1^1111))&&visited[x][y-10]==0){
search(x,y-10,index);
visited[x][y-10] =1;
}
if(out_of_index(x-10,y)&&(con[x-10][y]==1||con[x-10][y]==(-1^1111))&&visited[x-10][y]==0){
search(x-10,y,index);
visited[x-10][y] =1;
}
if(out_of_index(x-10,y+10)&&(con[x-10][y+10]==1||con[x-10][y+10]==(-1^1111))&&visited[x-10][y+10]==0){
search(x-10,y+10,index);
visited[x-10][y+10] =1;
}
if(out_of_index(x-10,y-10)&&(con[x-10][y-10]==1||con[x-10][y-10]==(-1^1111))&&visited[x-10][y-10]==0){
search(x-10,y-10,index);
visited[x-10][y-10] =1;
}
}
}
void cutter(int x, int y){
/*
函数说明：这里包含四把刀
参数说明：传入我们的起始坐标
*/
//首先判断点的位置：框内？框外？
for (int i = 0; i <801; i++) {
for (int j =0; j < 801; j++) {
visited[i][j] = 0;
}
}
if(y < -200){
//在下方
flag =0; //在下方外侧
search(x+400,y+400,1);
}
if(x < -300){
//在左侧！
flag = 0;
for (int i = 0; i <801; i++) {
for (int j =0; j < 801; j++) {
visited[i][j] = 0;
}
}
glPointSize(pixel_size);
glColor3f(0.9,0.89,0.1);
glBegin(GL_POINTS);
glVertex3f(translater(x_1-400),translater(y_1-400),0.0);
glEnd();
glFlush();
cout << "xx "<< x_1 -400 <<" " << y_1-400 <<endl;
search(x_1,y_1,2);
}
}
void p(float x , float y,float x1,float y1){
/*
函数说明：绘制像素的点，这里将点的大小设置为7。
颜色采用蓝色。利用圆八个部分的坐标对应关系进行绘图。
加x1与y1是为了进行圆的平移
参数说明：浮点数x，y是openGl坐标系。
*/
glPointSize(pixel_size);
glColor3f(1.0,1.0,0.0);
glBegin(GL_POINTS);
glVertex3f(x+x1,y+y1,0.0);
glEnd();
glFlush();
}
void paint(int x ,int y ){
add(x,y, 1);
p(translater(x), translater(y), 0, 0);
}
void grid(){
/*
函数说明：绘制网格为了便于将真实的像素pixel转化为我们模拟的像素
*/
glClearColor(0, 0, 0, 0);//这是设置背景色,必须要在glclear之前调用
glClear(GL_COLOR_BUFFER_BIT);
int hei_number = numbers;
float delta_hei = height / hei_number;
glColor3f(0.0,1.0,0);
for (int i = 1; i < numbers *2; i ++ ) { //利用循环绘制网格
glBegin(GL_LINES);
glVertex2f(-1+i*delta_hei/height, -1);
glVertex2f(-1+i*delta_hei/height, 1);
glVertex2f(-1,-1+i*delta_hei/height);
glVertex2f(1,-1+i*delta_hei/height);
glEnd();
glFlush();}
glColor3f(1.0,0,0);
glBegin(GL_LINES); //绘制坐标系，便于观察
glVertex2f(-1,0);
glVertex2f(1,0);
glVertex2f(0,-1);
glVertex2f(0,1);
glEnd();
glFlush();
//绘制我们的框图
for (int i = 0; i <= 300; i+=t) {
draw_point(translater( i),translater(200));
add(i, 200, -1);
add(-i, 200, -1);
add(i, -200, -1);
add(-i, -200, -1);
}
for (int i = 0; i <= 200; i+=t) {
draw_point(translater(300),translater( i));
add(300,i, -1);
add(-300,i, -1);
add(300,-i, -1);
add(-300,-i, -1);
}
//绘制多边形
int dm = -370;
//设置偏移量
for (int i = 140; i<=240; i+=10) {
paint(i, i+dm);
}
for(int i =240; i <=340 ; i+=10 ){
paint(240, i+dm);
//绘制横线
}
for(int i = 240;i>=-200;i-=10 ){
paint(i, 340+dm);
}
for(int i = -200;i>=-380;i-=10){
paint(i, 540+i+dm);
}
for(int i = -200;i>=-380;i-=10){
paint(i, 540+i+dm);
}
for(int i = 160; i >= -20 ; i-=10){
paint(-380, i+dm);
}
for (int i = 1;i <=30; i++) {
paint(-380+i*10, -20+i*10+dm);
}
for (int i = 1;i <=14; i++) {
paint(-80+i*10, 280-i*10+dm);
}
for(int i =60; i <=140 ; i+=10 ){
paint(i, 140+dm);
}
cutter(-380, -390);
//刷新缓冲，保证绘图命令能被执行
}
int main(int argc, char *argv[]) {
//初始化GLUT library
glutInit(&argc, argv);
//对窗口的大小进行初始化
glutInitWindowSize(700,700);
glutInitWindowPosition(300,200);
// 设置窗口出现的位置
//glutInitWindowPosition(int x, int y);
glutInitDisplayMode(GLUT_RGBA);
glutCreateWindow("hw_多边形裁剪");
glutDisplayFunc(&grid);
glutMainLoop();
return 0;
}