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[DirectX9] Rotating Triangle while flat...

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I am learning to use DirectX via DirectXTutorial.com and I am having trouble doing the suggested exercises. I am doing Direct3D Basics Lesson 5: Transforming Vertices. I am attempting to do exercise number four but I am kind of at a loss and would greatly appreciate some help to get over this hump. Here is the question and the website: "Now make the triangle lie flat while it rotates (be careful, it can only be seen from one side)." http://www.directxtutorial.com/Tutorial9/B-Direct3DBasics/dx9B5.aspx (Source code is near the bottom on a spoiler button) The lesson is learn what the three Transformations(World, View, Projection) are and how they work. The only thing I can think of is to change the X and Y coordinates of the vertices. Any and all help, suggestions, and criticism is greatly appreciated.
void render_frame(void)
{
    d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);

    d3ddev->BeginScene();

    // select which vertex format we are using
    d3ddev->SetFVF(CUSTOMFVF);

    // SET UP THE PIPELINE

    D3DXMATRIX matRotateY;    // a matrix to store the rotation information
	D3DXMATRIX matTranslate;  // a matrix to store the translation information
    static float index = 0.0f; index+=0.05f;    // an ever-increasing float value

    // build a matrix to rotate the model based on the increasing float value
    D3DXMatrixRotationY(&matRotateY, index);

    // tell Direct3D about our matrix
    d3ddev->SetTransform(D3DTS_WORLD, &(matRotateY * matTranslate));

    D3DXMATRIX matView;    // the view transform matrix

    D3DXMatrixLookAtLH(&matView,
                       &D3DXVECTOR3 (0.0f, 0.0f, 10.0f),    // the camera position
                       &D3DXVECTOR3 (0.0f, 0.0f, 0.0f),    // the look-at position
                       &D3DXVECTOR3 (0.0f, 1.0f, 0.0f));    // the up direction

    d3ddev->SetTransform(D3DTS_VIEW, &matView);    // set the view transform to matView

    D3DXMATRIX matProjection;     // the projection transform matrix

    D3DXMatrixPerspectiveFovLH(&matProjection,
                               D3DXToRadian(45),    // the horizontal field of view
                               (FLOAT)SCREEN_WIDTH / (FLOAT)SCREEN_HEIGHT, // aspect ratio
                               1.0f,    // the near view-plane
                               (indexRise));    // the far view-plane

    d3ddev->SetTransform(D3DTS_PROJECTION, &matProjection);    // set the projection

    // select the vertex buffer to display
    d3ddev->SetStreamSource(0, t_buffer, 0, sizeof(CUSTOMVERTEX));

    // copy the vertex buffer to the back buffer
    d3ddev->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 1);

    d3ddev->EndScene();

    d3ddev->Present(NULL, NULL, NULL, NULL);

    return;
}

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