[Source] 50% Bg Transparency in C++

void DrawBox(IDirect3DDevice8 *pD3Ddev, int x, int y, int w, int h, D3DCOLOR col)
{
struct QuadVertex {
float x,y,z,rhw;
DWORD dwColor;
};
IDirect3DVertexBuffer8 *pVertexBuffer = NULL;
QuadVertex qV[4];
BYTE *pVertexData = NULL;

if (pD3Ddev->CreateVertexBuffer((4*sizeof(QuadVertex)),(D3DUSAGE_WRITEONLY|D3DUSAGE_DYNAMIC),(D3DFVF_XYZRHW|D3DFVF_DIFFUSE),D3DPOOL_DEFAULT,&pVertexBuffer)<0) return;

pD3Ddev->SetRenderState(D3DRS_ZENABLE , FALSE);
pD3Ddev->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
pD3Ddev->SetRenderState(D3DRS_LIGHTING, FALSE);

pVertexBuffer->Lock(0,0,&pVertexData,D3DLOCK_NOSYSLOCK | D3DLOCK_DISCARD);
if(pVertexData)
{
qV[0].dwColor = qV[1].dwColor = qV[2].dwColor = qV[3].dwColor = col;
qV[0].z = qV[1].z = qV[2].z = qV[3].z = 0.0f;
qV[0].rhw = qV[1].rhw = qV[2].rhw = qV[3].rhw = 0.0f;

qV[0].x = (float)x;
qV[0].y = (float)(y + h);
qV[1].x = (float)x;
qV[1].y = (float)y;
qV[2].x = (float)(x + w);
qV[2].y = (float)(y + h);
qV[3].x = (float)(x + w);
qV[3].y = (float)y;

memcpy(pVertexData,qV,sizeof(QuadVertex)*4);
pVertexBuffer->Unlock();
pVertexData = NULL;

pD3Ddev->SetStreamSource(0,pVertexBuffer, sizeof(QuadVertex));
pD3Ddev->SetVertexShader( D3DFVF_XYZRHW | D3DFVF_DIFFUSE );
pD3Ddev->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 2 );
}
if (pVertexBuffer) {
pVertexBuffer->Release();
pVertexBuffer=NULL;
}
pD3Ddev->SetRenderState(D3DRS_LIGHTING, true);
}