Question

I m 碰到一个奇怪的开放式GL Bug。开放式教育对我来说是很新的,但我们要求将其用于我的独立职业学校(因为教师实际上是制图教授)。

无论是哪种方式,情况都是:http://img818.imageshack.us/img818/422/reversiothello.png”http://img818.imageshack.us/img818/422/reversiothello.png/a。

这只发生在最顶端,最左.。换言之,它发现最恶劣的多环形断裂,然后是最恶劣的,它确实如此。 (目前还不是从板上抹掉多角。)

我的展示职能是:

void display_func(void)
{
    glClearColor(0.0, 0.45, 0.0, 1.0); // Background Color (Forest Green :3)
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0, 0.0, 0.0);

    draw_board();

    glFlush();

    glutSwapBuffers();
};

My draw_board function is this:

void draw_board()
{
    int size = 8;
    int stepX = WINDOW_XS / size;
    int stepY = WINDOW_YS / size;

    glColor3f(0.0,0.0,0.0); // line color black

    glBegin(GL_LINES);

    // Draw Columns
    for(int i = 0;i <= WINDOW_XS;i += stepX)
    {
        glVertex2i(i,0);
        glVertex2i(i, WINDOW_YS);
    }

    // Draw Rows
    for(int j = 0;j <= WINDOW_YS;j += stepY)
    {
        glVertex2i(0, j);
        glVertex2i(WINDOW_XS, j);
    }

    // Draw Circles
    for(int i = 0;i < 8;++i)
    {
        for(int j = 0;j < 8;++j)
        {
            if(engine->getOnBoard(i,j) == Reversi::PIECE_NONE) continue;
            if(engine->getOnBoard(i,j) == Reversi::PIECE_WHITE)
                glColor3f(1.0,1.0,1.0);
            if(engine->getOnBoard(i,j) == Reversi::PIECE_BLACK)
                glColor3f(0.0,0.0,0.0);

            int drawX = ((i+1)*64)-32;
            int drawY = 512-((j+1)*64)+32;
            gl_drawCircle(drawX,drawY,30);
        }
    }

    glEnd();
};

我的改变职能是:

void mouse_func(int button, int state, int x, int y)
{
    if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN && x < WINDOW_XS)
    {    
        // row and column index
        x = (int)( x / (WINDOW_XS/8) );
        y = (int)( y / (WINDOW_YS/8) );

        std::cout << "Attempting to make a move at " << x << "," << y << std::endl;

        if(engine->makeMove(x,y))
        {
            glutPostRedisplay();
        }
    }
};

and my gl_drawCircle function is this:

void gl_drawCircle(float x, float y, float r)
{
    // http://stackoverflow.com/questions/5094992/c-drawing-a-2d-circle-in-opengl/5095188#5095188
    glBegin( GL_POLYGON );
    float t;
    int n;
    for(t = 0,n = 0; n <= 90; ++n, t = float(n)/90.f ) // increment by a fraction of the maximum 
    {
        glVertex2f( x + sin( t * 2 * PI ) * r, y + cos( t * 2 * PI ) * r );
    }
    glEnd();
}

谁能帮助我?

Answer 1

The only bug worth giving an answer that I can find is that your draw_board function doesn t use properly the glBegin and glEnd statements. You have to use a glEnd statement before calling gl_drawCircle, otherwise you ll get a nasty behavior.

Edit: 您首先使用“glBegin 被忽视(因为你在glBegin上)。所有其他圈子都是ok,因为你在打上<条码>(glEnd前再读到<条码>。第一圈是左上、最上层。

Answer 2

You need a call to glEnd after drawing the rows. When you do not call glEnd, OpenGL ignores your call glBegin( GL_POLYGON ); and assumes you still want to draw lines.

So just adding glEnd (); after drawing the rows should solve it.

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