Question

我想了解当我点击鼠标按钮时如何围绕其中心旋转多边形？

glBegin(GL_POLYGON); //drawing a pentagon and coloring it.(using a polygon GL)
    glColor3f(0, 0, 1);//Blue   
    glVertex3f(0.0f, 0.7f, 0.0f);//top point
    glColor3f(1, 0.5, 0);//Orange
    glVertex3f(-0.5f, 0.3f, 0.0f);//left middle point
    glColor3f(0, 1, 0);//Green
    glVertex3f(-0.3f, -0.3f, 0.0f);//bottom left point
    glColor3f(0.53, 0.12, 0.47);//Purple
    glVertex3f(0.3f, -0.3f, 0.0f);//bottom right point
    glColor3f(1, 0, 0);//red
    glVertex3f(0.5f, 0.3f, 0.0f);//middle right point
    glEnd();
    glutSwapBuffers();//Sends the Scene to the window

}

void mouse(int button, int state, int x, int y){
    if (button == GLUT_RIGHT_BUTTON){
        glRotatef(angle, 0, 0, 1);
        }
    }

Answer 1

最简单的方法是将旋转角度存储在全局变量中。这将是这样的：

global:
float angle = 0;

draw:
glRotate(angle, 0, 0, 1);
glBegin(GL_POLYGON);
...

void mouse(int button, int state, int x, int y){
    if (button == GLUT_RIGHT_BUTTON)
        angle += A_VALUE_PER_CLICK;
}

编辑：注意，只要您点击（按要求），上述内容就会旋转。如果你想要旋转对象，只要按下鼠标，你就必须做一点不同的事情：

global:
bool is_mouse_down = false;
float angle = 0;

draw:
if (is_mouse_down)
    angle += ANGLE_PER_FRAME;

glRotate(angle, 0, 0, 1);
glBegin(GL_POLYGON);
...

void mouse(int button, int state, int x, int y){
    if (button == GLUT_RIGHT_BUTTON) {
        if (state == GLUT_DOWN)
            is_mouse_down = true;
        if (state == GLUT_UP)
            is_mouse_down = false;
    }
}

编辑2：要旋转特定点（在这种情况下是多边形的中心[0,0.2,0]），必须始终将此点转换为原点，然后旋转然后将其平移。这意味着必须使用类似这样的代码（标志可能会被翻转）：

draw:
glTranslate(0, 0.2, 0);
glPushMatrix();
glRotate(angle, 0, 0, 1);
glPushMatrix();
glTranslate(0, -0.2, 0);

//Draw

glPopMatrix();
glPopMatrix();

如何在鼠标单击时围绕其中心旋转多边形？

1 个答案: