How good is directx normal calculation

Hi;

I've created a small (5 vertex by 5 vertex) heightfield mesh with adjacency information.

The mesh is flat in the x-z plane, with a single overhead light.

I raise a single point in the cente of the mesh, thus creating a small four-sided pyramid. I then recalculate the normals using mesh.computenormals.But instead of getting a symettrically shaded pyramid, I get an asymmetrical mess. The pyramid is fine, but the shading is wrong.

As far as I can tell, this is actually the directx normal calculation going wrong -- perhaps because it doesn't use weighted vertices?

I've attached a picture of the result here. Does anyone know why it looks like this? Is the default normal calculation really that bad or did I mess something up?

Here is how I modify the mesh:

And here is the awful result:

http://img241.imageshack.us/my.php?image=imageqw4.jpg

Regards...

[1239 byte] By [ImagineNation] at [2007-12-23]