//semi-circle roof
    //fix variable naming
    int centerx = 400;//x axis center
    int centery = 400;//y axis center
    int roofr = 100;//radius
    int roofd = 200;//diameter
    float PI = 3.141592653589793238f;
    float semicircleangle = PI * 1.0f;
    int steps = 100;
    glBegin(GL_TRIANGLE_FAN);

    for (int i = 0; i < steps; i++) {
        float theta = semicircleangle * float(i) / float(steps);//get the current angle
        float x = roofr * cosf(theta);//calculate the x component
        float y = roofr * sinf(theta);//calculate the y component
        glVertex2f(x + centerx, y + centery);//output vertex

    }
    glEnd();