感谢迄今为止所有的回复。
我已经弄清楚如何做到这一点,所以我将继续回答我自己的问题。
我使用 GLUT 作为鼠标处理程序:
当单击鼠标并移动 (glutMotionFunc) 时,将调用拖动函数。
在拖动函数中,鼠标坐标 (x,y) 在转换为窗口坐标时会转换为 Points 结构。
如果鼠标位于方块内,则通过更改其坐标来拖动方块并重新显示。
我对 OpenGL 和 C++ 还很陌生,所以我对混乱的编码表示歉意。我对这样做有点沮丧,因为重新绘制的正方形使得光标看起来捕捉到了中心。我欢迎出于学习目的对此问题的替代解决方案以及对我的代码的批评。
代码(包括 glut 和 using 命名空间 std):
// points structure made of two coordinates; x and y
struct Points
{
float x,y; // initializor
Points() { x = 0.0; y = 0.0; } // constructor
Points(float _x, float _y) : x(_x), y(_y) {}
};
// square made of 4 points
class Square
{
public:
Points pts[4]; // square structure
Square(); // initialize constructor
void draw(Square *sqr); // draw square
Points mouse(int x, int y); // get mouse coordintaes
Square* drag(Square *sqr, Points *mouse); // change points of sqr
};
// square constructor
Square::Square()
{
pts[0] = Points(0.2,0.2);
pts[1] = Points(0.4,0.2);
pts[2] = Points(0.4,0.4);
pts[3] = Points(0.2,0.4);
};
// draw function
void Square::draw(Square *sqr)
{
// draw square fill
int i;
glColor3f(0.2, 0.2, 0.2);
glBegin(GL_QUADS);
for (i = 0; i < 4; ++i)
{
glVertex2f(sqr->pts[i].x, sqr->pts[i].y);
}
glEnd();
// draw square points
i = 0;
glColor3f(1.0, 1.0, 1.0);
glBegin(GL_POINTS);
for (i = 0; i < 4; ++i)
{
glVertex2f(sqr->pts[i].x, sqr->pts[i].y);
}
glEnd();
}
// mouse function
Points Square::mouse(int x, int y)
{
int windowWidth = 400, windowHeight = 400;
return Points(float(x)/windowWidth, 1.0 - float(y)/windowHeight);
}
// drag function
Square* Square::drag(Square *sqr, Points *mouse)
{
sqr->pts[0].x = mouse->x - 0.1;
sqr->pts[0].y = mouse->y - 0.1;
sqr->pts[1].x = mouse->x + 0.1;
sqr->pts[1].y = mouse->y - 0.1;
sqr->pts[3].x = mouse->x - 0.1;
sqr->pts[3].y = mouse->y + 0.1;
sqr->pts[2].x = mouse->x + 0.1;
sqr->pts[2].y = mouse->y + 0.1;
return sqr;
}
// GLOBAL
// create square object
Square* sqr = new Square;
// display at start
void display() {
glClear(GL_COLOR_BUFFER_BIT);
sqr->draw(sqr);
glFlush();
}
// drag function
void drag (int x, int y)
{
// int x and y of mouse converts to screen coordinates
// returns the point as mousePt
Points mousePt = sqr->mouse(x,y);
//create pointer to window point coordinates
Points* mouse = &mousePt;
// if the mouse is within the square
if (mouse->x > sqr->pts[0].x && mouse->y > sqr->pts[0].y)
{
if (mouse->x < sqr->pts[2].x && mouse->y < sqr->pts[2].y)
{
// then drag by chaning square coordinates relative to mouse
sqr->drag(sqr,mouse);
glutPostRedisplay();
}
}
}
void Initialize() {
glClearColor(0.0, 0.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}
int main(int iArgc, char** cppArgv) {
glutInit(&iArgc, cppArgv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(400, 400);
glutInitWindowPosition(200, 200);
glutCreateWindow("Move Box");
glutMotionFunc(drag);
Initialize();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}