实验2

lab2/lab2.cpp

@@ -0,0 +1,175 @@
+#include <GL/glut.h>
+#include <iostream>
+
+// --- 定义区域编码 ---
+#define INSIDE 0 // 0000
+#define LEFT   1 // 0001
+#define RIGHT  2 // 0010
+#define BOTTOM 4 // 0100
+#define TOP    8 // 1000
+
+// --- 定义裁剪窗口结构 ---
+struct ClipWindow {
+    float xmin, xmax, ymin, ymax;
+};
+
+// --- 全局变量设置 ---
+ClipWindow rect;
+int x_0, y_0, x_1, y_1; // 线段端点
+
+/**
+ * 计算点 (x, y) 的区域编码
+ */
+int computeCode(float x, float y, ClipWindow rect) {
+    int code = INSIDE;
+    if (x < rect.xmin)      code |= LEFT;
+    else if (x > rect.xmax) code |= RIGHT;
+    if (y < rect.ymin)      code |= BOTTOM;
+    else if (y > rect.ymax) code |= TOP;
+    return code;
+}
+
+/**
+ * Cohen-Sutherland 算法核心
+ * 注意：这里传入坐标的引用，直接修改坐标值以得到裁剪后的结果
+ */
+void cohenSutherlandClip(float& x_0, float& y_0, float& x_1, float& y_1, ClipWindow rect) {
+    int code1 = computeCode(x_0, y_0, rect);
+    int code2 = computeCode(x_1, y_1, rect);
+    bool accept = false;
+
+    while (true) {
+        // 如果两端点都在窗口内 (0000 | 0000 == 0)
+        if (!(code1 | code2)) {
+            accept = true;
+            break;
+        }
+        // 如果两端点都在窗口的同一侧外部 (例如都在左边：0001 & 0001 != 0) 按位与运算
+        else if (code1 & code2) {
+            break; // 直接舍弃
+        }
+        // 3. 线段部分在窗口内，需要求交点
+        else {
+            int code_out;
+            float x, y;
+
+            // 选择窗口外的一个端点
+            if (code1 != 0)
+                code_out = code1;
+            else
+                code_out = code2;
+
+            // 计算交点
+            if (code_out & TOP) {
+                x = x_0 + (x_1 - x_0) * (rect.ymax - y_0) / (y_1 - y_0);
+                y = rect.ymax;
+            }
+            else if (code_out & BOTTOM) {
+                x = x_0 + (x_1 - x_0) * (rect.ymin - y_0) / (y_1 - y_0);
+                y = rect.ymin;
+            }
+            else if (code_out & RIGHT) {
+                y = y_0 + (y_1 - y_0) * (rect.xmax - x_0) / (x_1 - x_0);
+                x = rect.xmax;
+            }
+            else if (code_out & LEFT) {
+                y = y_0 + (y_1 - y_0) * (rect.xmin - x_0) / (x_1 - x_0);
+                x = rect.xmin;
+            }
+
+            // 用交点替换原来的外部端点
+            if (code_out == code1) {
+                x_0 = x; y_0 = y;
+                code1 = computeCode(x_0, y_0, rect);
+            }
+            else {
+                x_1 = x; y_1 = y;
+                code2 = computeCode(x_1, y_1, rect);
+            }
+        }
+    }
+
+    // 如果接受，则绘制裁剪后的线段（蓝色）
+    if (accept) {
+        glBegin(GL_LINES);
+        glColor3f(0.0f, 0.0f, 1.0f); // 蓝色
+        glVertex2f(x_0, y_0);
+        glVertex2f(x_1, y_1);
+        glEnd();
+    }
+}
+
+// --- 显示回调函数 ---
+void myDisplay() {
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    // 1. 绘制裁剪窗口 (红色线框)
+    glColor3f(1.0f, 0.0f, 0.0f); // 红色
+    glBegin(GL_LINE_LOOP);
+        glVertex2f(rect.xmin, rect.ymin);
+        glVertex2f(rect.xmax, rect.ymin);
+        glVertex2f(rect.xmax, rect.ymax);
+        glVertex2f(rect.xmin, rect.ymax);
+    glEnd();
+
+    // 2. 绘制原始线段 (绿色)
+    // 注意：为了演示效果，我们在调用裁剪函数前，先保存原始坐标，
+    // 或者在这里直接用初始值绘制。这里我们使用初始值绘制。
+    int orig_x_0 = 50, orig_y_0 = 350;
+    int orig_x_1 = 550, orig_y_1 = 50;
+
+    glBegin(GL_LINES);
+    glColor3f(0.0f, 1.0f, 0.0f); // 绿色
+    glVertex2f(orig_x_0, orig_y_0);
+    glVertex2f(orig_x_1, orig_y_1);
+    glEnd();
+
+    // 3. 执行裁剪并绘制结果 (蓝色)
+    // 使用 float 变量传入，因为算法内部会修改它们
+    float cx_0 = orig_x_0, cy_0 = orig_y_0;
+    float cx_1 = orig_x_1, cy_1 = orig_y_1;
+    
+    // 加粗蓝色线条以便区分
+    glLineWidth(3.0); 
+    cohenSutherlandClip(cx_0, cy_0, cx_1, cy_1, rect);
+    glLineWidth(1.0); // 恢复线宽
+
+    glFlush();
+}
+
+// --- 初始化设置 ---
+void Init() {
+    glShadeModel(GL_FLAT);
+
+    rect.xmin = 100;
+    rect.xmax = 400;
+    rect.ymin = 100;
+    rect.ymax = 300;
+}
+
+// --- 窗口大小调整 ---
+void myReshape(int w, int h) {
+    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
+    glMatrixMode(GL_PROJECTION);
+    glLoadIdentity();
+    // 设置二维投影范围，与坐标数值对应
+    gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);
+    glMatrixMode(GL_MODELVIEW);
+}
+
+// --- 主函数 ---
+int main(int argc, char* argv[]) {
+    glutInit(&argc, argv);
+    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
+    glutInitWindowPosition(100, 100);
+    glutInitWindowSize(600, 400);
+    glutCreateWindow("实验2_03毕爽爽 Cohen-Sutherland 算法");
+
+    Init();
+
+    glutDisplayFunc(myDisplay);
+    glutReshapeFunc(myReshape);
+
+    glutMainLoop();
+    return 0;
+}