I couldn't do the averaging in the terrain shader since it only has very local access to one vertex at a time. In practice, though, it is a bit more tricky.

This creates a gap in the mesh:Ĭonceptually, my solution was to force the heights of the extra middle points on the edge of the more detailed grid to be the average of the two points on either side - essentially simulating the edges of the neighboring, less detailed grid. As you can see below, where the two rings share an edge, the more detailed ring samples an extra height point between each point on the less detailed ring. The situation that creates seams is the edge between one ring and the next ring with half as many grid squares. I'll see if I can explain it in a way that makes sense. Yesterday I finally came up with a good solution. I really didn't want to resort to that unless I had to. Most techniques for handling seams revolve around adding extra geometry to 'stitch' the edges together. It took me a while before I came up with a solution to the seam problem that I was happy with. As you can see below, this is clearly not acceptable: Where one level of detail meets the next, you get discontinuities in the terrain. The down side is that you have to deal with seams. The big win you get from doing this is that the number of triangles you need to draw increases linearly with the size of the terrain, rather than exponentially with the area. As the camera moves, the grid moves with it so that the highly detailed area is always nearby. With each successive ring, the grid size is doubled. Instead of the terrain being composed of a single grid mesh, it is now broken down into concentric square 'rings'. That worked ok, but it was inefficient and I knew I would eventually outgrow it.Ībove, you can see my current method for doing terrain LOD. I could increase or decrease the detail of the island based on distance, but the entire island had the same level of detail. Initially, I was doing LOD on an entire island-by-island basis. Terrain has a particular characteristic that you don't usually have to deal with when doing LOD for other kinds of objects (ie: trees, etc.) - it is continuous.

Handling Level-Of-Detail (LOD) gracefully for terrain turns out to be tougher than you might expect.

Terragen butte tutorial