QTS no. 10 - World to screen

/*
-----------------------------------------
* Game hacking QTS ( Quickie Tip Series )
* no. 10 - World to screen
-----------------------------------------
* Author: SEGnosis  - GHAnon.net
* Thanks to:
* bitterbanana      - No known site
* Drunken Cheetah   - No known site
* fatboy88      - No known site
* Geek4Ever         - No known site
* learn_more        - www.uc-forum.com
* Novocaine         - http://ilsken.net/blog/?page_id=64
* Philly0494        - No known site
* Roverturbo        - www.uc-forum.com
* SilentKarma       - www.halocoders.com - offline
* Strife        - www.uc-forum.com
* Wieter20      - No known site
*/

#define IsW2SValid(a)( ( a.x == -1000 && a.y == -1000 ) ? false : true )


struct FVect3
{
    float x,y,z;
};


//----------------------------------//
POINT World2Screen( FVect3 vPos )
{
    POINT ptRet = { -1000, -1000 };

    D3DXVECTOR3 vScreen,
                vWorld( vPos.x, vPos.y, vPos.z );

    static D3DXMATRIX   m_mxProjection,
                        m_mxView,
                        m_mxWorld;

    pDevice->GetTransform( D3DTS_VIEW, &m_mxView );

    pDevice->GetTransform( D3DTS_PROJECTION, &m_mxProjection );

    pDevice->GetTransform( D3DTS_WORLD, &m_mxWorld );

    pDevice->GetViewport( &m_ViewPort );

    D3DXVec3Project( &vScreen, &vWorld, &m_ViewPort, &m_mxProjection, &m_mxView, &m_mxWorld );

    if( vScreen.z <= 1 )
    {
        ptRet.x = vScreen.x;
        ptRet.y = vScreen.y;
    }

    return ptRet;
}
//----------------------------------//