How can I get projected coordinates of vertex on screen

Question

I want to check picking for faces and for that I need projected X Y coordinates of my vertexes in -1 to 1 range:
For that I multiply my vertex array with matrices and then get projected triangle coordinates from it and check if mouse is inside of that triangle ,but something goes wrong:
Here is my code

    for (int i = 0; i < m_vertexCount; ++i)
{
    D3DXVec4Transform(&m_Pverts1[i], &m_Pverts[i], &worldmatrix);
    D3DXVec4Transform(&m_Pverts1[i], &m_Pverts[i], &viewmatrix);
    D3DXVec4Transform(&m_Pverts1[i], &m_Pverts[i], &projectionmatrix);
}
z = 0;
for (int i = 0; i < m_faceCount; ++i)
{
    x1 = m_Pverts1[m_verts[z].x - 1].x / m_Pverts1[m_verts[z].x - 1].w;
    y1 = m_Pverts1[m_verts[z].x - 1].y / m_Pverts1[m_verts[z].x - 1].w;
    z1 = m_Pverts1[m_verts[z].x - 1].z / m_Pverts1[m_verts[z].x - 1].w; ++z;
    x2 = m_Pverts1[m_verts[z].x - 1].x / m_Pverts1[m_verts[z].x - 1].w;
    y2 = m_Pverts1[m_verts[z].x - 1].y / m_Pverts1[m_verts[z].x - 1].w;
    z2 = m_Pverts1[m_verts[z].x - 1].z / m_Pverts1[m_verts[z].x - 1].w; ++z;
    x3 = m_Pverts1[m_verts[z].x - 1].x / m_Pverts1[m_verts[z].x - 1].w;
    y3 = m_Pverts1[m_verts[z].x - 1].y / m_Pverts1[m_verts[z].x - 1].w;
    z3 = m_Pverts1[m_verts[z].x - 1].z / m_Pverts1[m_verts[z].x - 1].w; ++z;

    //code .. //
}

Where m_Pverts is array of vertexes m_Pverts1 is empty array for transformed vertexes and m_verts[].x is array of vertex indexes: x1,y1,z1,x2,y2,z3,x3,y3,z3 must be X Y projected coordinates of triangle and Z depth:
Other code is checked and works right:

What I am doing wrong ??

Answer 1

I get the solution of my problem: Instead of using worldmatrix viewmatrix and projectionmatrix
i must use wvpwatrix which is multiplication of that three matrices

D3DXMATRIX wvp;

wvp = worldmatrix*viewmatrix*projectionmatrix;

for (int i = 0; i < m_vertexCount; ++i)
{
    D3DXVec3TransformCoord(&m_Pverts1[i], &m_Pverts[i], &wvp);
}

But I dont know why is it working??