Something

struct COSTUMVERTEX{
	FLOAT x,y,z;
	DWORD color;
	FLOAT U, V;
};

VOID InitPlaneTransparency(LPDIRECT3DVERTEXBUFFER9 &myvertexbuffer){
	COSTUMVERTEX t_vert[4];
	VOID* pVoid;

	// kopi data dari myvertexbuffer ke t_vert[4]
	myvertexbuffer->Lock(0,0, (void**)&pVoid, 0);	
	memcpy(t_vert, pVoid, sizeof(t_vert));
	myvertexbuffer->Unlock();

	// modifikasi data t_vert
	for(int i=0;i<4;i++){
 		t_vert[i].x=0;
 		t_vert[i].y=0;
 		t_vert[i].z=0;          
		t_vert[i].color=D3DCOLOR_ARGB(255,255,255,255);
	}

	// kopi lagi dari t_vert ke myvertexbuffer
	myvertexbuffer->Lock(0,0, (void**)&pVoid, 0);	
	memcpy(pVoid, t_vert, sizeof(t_vert));
	myvertexbuffer->Unlock();
}