在OpenGL中绘制条纹(C++)

Question

我在C++中关注OpenGL的xoax.net教程,并且我坚持使用for循环在US标志中绘制条纹.我只是得到一个蓝色的屏幕(因为我将背景颜色设置为蓝色).这是'DrawStripes'函数的代码:

void DrawStripes() {
for (int x = 0; x < 13; ++x) {
    if (x % 2 == 0) {
        glColor3f(204/255, 0, 0);
    } else {
        glColor3f(1, 1, 1);
    }

    float fStartX = 0;
    float fEndX = 1;
    float fStartY = x * (1/13);
    float fEndY = (x + 1) * (1/13);

    if (x > 5) {
        fStartX = .76/1.9;
    }
    glBegin(GL_QUADS);
    glVertex3f(fStartX, fStartY, 0);
    glVertex3f(fEndX, fStartY, 0);
    glVertex3f(fEndX, fEndY, 0);
    glVertex3f(fStartX, fEndY, 0);
    glEnd();
    }
}

(我把这个函数放在'draw'函数中,所以我不是告诉它使用这个函数)任何想法？

---编辑---这是'Draw'和'Initialize'函数:

void Draw() {
glClear(GL_COLOR_BUFFER_BIT);
    DrawStripes();
    glFlush();
}

void Initialize() {
glClearColor(0.0, 0.0, 0.5, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

Answer 1

C++中1/13为0.去过也做过.对于浮点常量,您要使用1.0f/13.0f.