   How to tranform vertex in  world coordinate to screen cord
  please suggest me  
  build a perspective projection matrix, and possibly also a camera orientation/position matrix, and them transform the vertex with them? It''s quite easy. I''m sure you can even have D3DX to build them for you.;  1.) get the ''modelview'' matrix2.) get the ''projection'' matrix3.) calculate the product of the ''perspection'' matrix and the ''modelview'' one4.) multiply the product with the vertex''s position. the vertex then is in clipping space5.) divide the clipped vertex position by it''s fourth (w) component6.) multiply the x- and y- components of that vector with the screen''s x- and y- dimensions   