在LWJGL中使用glArrayElement

Question

I'm following along with the OpenGL tutorial found here . I'm on chapter 2 right now and it's going over the advantages of using glArrayElement to render objects. Currently, my code is as follows:

glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);

    double vertices[] = {100, 200, 0, 200, 100, 0, 100, 100, 0};
    double colors[] = {1, .5, .8, .3, .5, .8, .3, .5, .8};


    DoubleBuffer vertexBuffer = BufferUtils.createDoubleBuffer(9).put(vertices);
    DoubleBuffer colorBuffer = BufferUtils.createDoubleBuffer(9).put(colors);

    glVertexPointer(3, 0, vertexBuffer);
    glColorPointer(3, 0, colorBuffer);

    while(!Display.isCloseRequested()) {

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glBegin(GL_TRIANGLES);
        glArrayElement(0);
        glArrayElement(1);
        glArrayElement(2);
        glVertex3d(300, 200, 0);
        glVertex3d(400, 100, 0);
        glVertex3d(300, 100, 0);
        glEnd();

        //Display.sync(60);
        Display.update();
    }

The second triangle, defined explicitly by calls to glVertex3d is rendered fine. Bu the first triangle does not render at all. Am I making a simple mistake?

Answer 1

While scouring for more sample code, I came across a snippet that said you had to "flip each buffer." Adding

vertexBuffer.flip();
colorBuffer.flip();

Right before the while loop solved my problem!