Falsche World2Screen Berechnung

class Engine
{
public:
    virtual void    function1() = 0;
    virtual void    function2() = 0;
    virtual void    function3() = 0;
    virtual void    function4() = 0;
    virtual void    function5() = 0;
    virtual void    function6() = 0;
    virtual void    function7() = 0;
    virtual void    function8() = 0;
    virtual bool    GetPlayerInfo(int ent_num, player_info_t *pinfo) = 0;
    virtual int     GetPlayerForUserID(int userID) = 0;
    virtual void    function9() = 0;
    virtual bool    Con_IsVisible() = 0;
    virtual int     GetLocalPlayer() = 0;
    virtual void    function10() = 0;
    virtual void    function11() = 0;
    virtual void    function12() = 0;
    virtual void    function13() = 0;
    virtual void    function14() = 0;
    virtual void    function15() = 0;
    virtual void    function16() = 0;
    virtual void    function17() = 0;
    virtual int     GetMaxClients() = 0;
    virtual void    function18() = 0;
    virtual void    function19() = 0;
    virtual void    function20() = 0;
    virtual void    function21() = 0;
    virtual bool    IsInGame() = 0;
    virtual void    function22() = 0;
    virtual void    function23() = 0;
    virtual void    function24() = 0;
    virtual void    function25() = 0;
    virtual void    function26() = 0;
    virtual void    function27() = 0;
    virtual void    function28() = 0;
    virtual void    function29() = 0;
    virtual void    function30() = 0;
    virtual float*  WorldToScreenMatrix() = 0;
};
 
bool ScreenTransform(Vector &point, Vector &screen)
{
    float w;
    float *WorldToScreen = engine->WorldToScreenMatrix(); //hier bekommste von der Engine die WorldToScreenMatrix
    screen.x = WorldToScreen[0] * point.x + WorldToScreen[1] * point.y + WorldToScreen[2] * point.z + WorldToScreen[3];
    screen.y = WorldToScreen[4] * point.x + WorldToScreen[5] * point.y + WorldToScreen[6] * point.z + WorldToScreen[7];
    w        = WorldToScreen[12] * point.x + WorldToScreen[13] * point.y + WorldToScreen[14] * point.z + WorldToScreen[15];
    screen.z = 0.0f;
 
    bool behind = false;
 
    if (w < 0.001f)
    {
        behind = true;
    }
    else
    {
        behind = false;
        float invw = 1.0f / w;
        screen.x *= invw;
        screen.y *= invw;
    }
    return behind;
}
//---------------------------------------------------------------------------
bool WorldToScreen(Vector &vOrigin, Vector &vScreen)
{
    if (ScreenTransform(vOrigin, vScreen) == false)
    {
        int iScreenWidth = gui.Viewport.Width, iScreenHeight = gui.Viewport.Height;
 
        float x = iScreenWidth / 2;
        float y = iScreenHeight / 2;
        x += 0.5 * vScreen.x * iScreenWidth + 0.5;
        y -= 0.5 * vScreen.y * iScreenHeight + 0.5;
        vScreen.x = x;
        vScreen.y = y;
        return true;
    }
    return false;
}