im using D3DXLine to convert some of the OpenGL codes to DX, just to using variable width lines. It works fine with the current World and View Matrix.. however if the line is big.. sometimes weird things starts happening.. like suddenly the X ordinate seems to get flipped or sometimes a part of the line disappears. However if the line length is small.. it works perfect. Any idea why this is happening

Any Idea ? or is there any way to render variable width lines in DX