OpenGL交互式画圆算法示例代码

下面是使用OpenGL编写的具有用户交互的画圆算法的示例代码。用户可以点击鼠标左键来确定圆的中心，然后拖动鼠标并松开左键来确定圆的半径。

#include <GL/glut.h>
#include <iostream>

// 圆参数
float centerX = 0.0f;
float centerY = 0.0f;
float radius = 0.0f;
bool isDrawing = false;

// 用于绘制圆
void drawCircle() {
    glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();

    if (radius > 0.0f) {
        glBegin(GL_LINE_LOOP);
        for (int i = 0; i < 360; i++) {
            float rad = i * 3.14159f / 180.0f;
            float x = centerX + radius * cos(rad);
            float y = centerY + radius * sin(rad);
            glVertex2f(x, y);
        }
        glEnd();
    }

    glFlush();
}

// 鼠标点击回调函数
void mouse(int button, int state, int x, int y) {
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) {
        centerX = (x - glutGet(GLUT_WINDOW_WIDTH) / 2) / (float)glutGet(GLUT_WINDOW_WIDTH) * 2.0f;
        centerY = -(y - glutGet(GLUT_WINDOW_HEIGHT) / 2) / (float)glutGet(GLUT_WINDOW_HEIGHT) * 2.0f;
        isDrawing = true;
    }
    else if (button == GLUT_LEFT_BUTTON && state == GLUT_UP) {
        float endX = (x - glutGet(GLUT_WINDOW_WIDTH) / 2) / (float)glutGet(GLUT_WINDOW_WIDTH) * 2.0f;
        float endY = -(y - glutGet(GLUT_WINDOW_HEIGHT) / 2) / (float)glutGet(GLUT_WINDOW_HEIGHT) * 2.0f;
        radius = sqrt(pow(endX - centerX, 2) + pow(endY - centerY, 2));
        isDrawing = false;
    }

    glutPostRedisplay();
}

// 鼠标拖动回调函数
void motion(int x, int y) {
    if (isDrawing) {
        float endX = (x - glutGet(GLUT_WINDOW_WIDTH) / 2) / (float)glutGet(GLUT_WINDOW_WIDTH) * 2.0f;
        float endY = -(y - glutGet(GLUT_WINDOW_HEIGHT) / 2) / (float)glutGet(GLUT_WINDOW_HEIGHT) * 2.0f;
        radius = sqrt(pow(endX - centerX, 2) + pow(endY - centerY, 2));
    }

    glutPostRedisplay();
}

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutCreateWindow('Interactive Circle');

    glClearColor(0.0, 0.0, 0.0, 1.0);
    gluOrtho2D(-1.0, 1.0, -1.0, 1.0);

    glutDisplayFunc(drawCircle);
    glutMouseFunc(mouse);
    glutMotionFunc(motion);

    glutMainLoop();

    return 0;
}

此代码使用OpenGL库实现了一个具有用户交互的画圆算法。用户可以点击鼠标左键来确定圆的中心，然后拖动鼠标并松开左键来确定圆的半径。圆的位置和半径的改变会即时更新在屏幕上。

请注意，此代码仅为演示目的，并未进行错误处理或优化。您可以根据自己的需求进行修改和扩展。希望对您有所帮助！