I have generated terrain from a grey-map file using height maps. I believed that I had created all the normals properly and it appeared to be mostly correct as far the lighting was concerned (there were a few issues which I think may be related to my problem). I have now realized that some of my normals appear to be going in the opposite direction while others appear to be fine. More specifically it appears that the normals in an up-slope are reversed (they go into the terrain instead of away from) but downslopes appear to be correct (or so I think anyways). I want to use the direction of the normal of each vertex to add grass to the terrain but because of my normal problems some of the grass is growing under the terrain. Any advice would be greatly appreciated. Thanks.
Are you sure you create all the triangles the same way? Clockwize or not.