多边形的扫描转换
实验环境
Visual Studio 2019
三、实验步骤/过程
#include
#include
#include
using namespace std;
int n;
struct vertex {
float ver_x;
float ver_y;
};
typedef struct XET {
float x;
float dx, ymax;
XET* next;
}AET, NET;
struct point {
float x;
float y;
};
vertex* ver;
inline void input() {
cout << "输入要显示的多边形共有几个顶点" << endl;
cin >> n;
ver = (vertex*)malloc(sizeof(vertex) * n);//输入顶点以（x,y）格式
for (int i = 0; i < n; i++) {
cout << "按顺序输入每个顶点的想x,y值，每输入完一个顶点，点击回车进入下一个顶点的输入" << endl;
cin >> ver[i].ver_x >> ver[i].ver_y;
}
}
void Polygon() {
int MaxY = 0;
int i;
for (i = 0; i < n; i++) {
if (ver[i].ver_y > MaxY)
MaxY = ver[i].ver_y;
}
AET* pAET = new AET;
pAET->next = NULL;
NET* pNET[1024];
for (i = 0; i <= MaxY; i++) {
pNET[i] = new NET;
pNET[i]->next = NULL;
}
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0, 0.0, 0.0);
glBegin(GL_POINTS);
for (i = 0; i < MaxY; i++) {
for (int j = 0; j < n; j++) {
if (ver[j].ver_y == i) {
if (ver[(j + 1 + n) % n].ver_y > ver[j].ver_y) {
NET* p = new NET;
p->x = ver[j].ver_x;
p->ymax = ver[(j + 1 + n) % n].ver_y;
p->dx = (ver[(j + 1 + n) % n].ver_x - ver[j].ver_x) / (ver[(j + 1 + n) % n].ver_y - ver[j].ver_y);
p->next = pNET[i]->next;
pNET[i]->next = p;
}
if (ver[(j - 1 + n) % n].ver_y > ver[j].ver_y) {
NET* p = new NET;
p->x = ver[j].ver_x;
p->ymax = ver[(j - 1 + n) % n].ver_y;
p->dx = (ver[(j - 1 + n) % n].ver_x - ver[j].ver_x) / (ver[(j - 1 + n) % n].ver_y - ver[j].ver_y);
p->next = pNET[i]->next;
pNET[i]->next = p;
}
}
}
}
glClear(GL_COLOR_BUFFER_BIT);
if (n % 2 == 0) {
glColor3f(1.0, 0.0, 0.0); // 设置当前色为红色
}
else
{
glColor3f(0.0, 0.0, 1.0); // 设置当前色为蓝色
}
glBegin(GL_POINTS);
for (i = 0; i <= MaxY; i++) {
AET* p = new AET;
p = pAET->next;
AET* n = new AET;
//将新边表中的活性边按照从左到右的顺序排序
if (pNET[i]->next && pNET[i]->next->next) {
if (pNET[i]->next->dx > 0) {
NET* t = new NET;
t = pNET[i]->next;
n = pNET[i]->next->next;
t->next = NULL;
n->next = NULL;
pNET[i]->next = n;
n->next = t;
}
}
//更新活性边表中的活性边x坐标的值
while (p) {
p->x = p->x + p->dx;
p = p->next;
}
p = pAET->next;
n = pAET;
//删掉扫描线高度等同于ymax的废弃点
while (p) {
if (p->ymax == i) {
n->next = p->next;
p = n->next;
}
else {
p = p->next;
n = n->next;
}
}
//插入新点，按照顺序插入
p = pAET->next;
n = pAET;
NET* a = new NET;
a = pNET[i]->next;
if (a) {
NET* b = new NET;
b = a;
while (b->next) {
b = b->next;
}
if (!pAET->next) {
pAET->next = a;
}
else {
while (p) {
if (a->x < p->x) {
b->next = p;
n->next = a;
break;
}
if (!p->next) {
p->next = a;
break;
}
n = n->next;
p = p->next;
}
}
}
//填充2
p = pAET->next;
while (p && p->next) {
for (float j = p->x; j <= p->next->x; j++) {
glVertex2i(static_cast<int>(j), i);
}
p = p->next->next;
}
}
glEnd();
glFlush();
}
void init(void) {
glClearColor(1.0, 1.0, 1.0, 0.0); //设置底色 红绿蓝和alpha值
glMatrixMode(GL_PROJECTION); //这个是投影的意思
gluOrtho2D(0.0, 600, 0.0, 450); //gluOrtho2D是指屏幕区域对应的模型坐标范围
}
int main(int argc, char* argv) {
glutInit(&argc, &argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowPosition(50, 100);
glutInitWindowSize(400, 300);
glutCreateWindow("图形学实验一");
input();
init();
glutDisplayFunc(Polygon);
glutMainLoop();
}
实验结果
