Far away objects clipping terrain at lower LOD levels

[SpiderPig]

Obviously, terrain needs LOD, but if you want to still see far away towns, boulders, trees or any other objects you're going to need to stop them clipping through the terrain as those far away patches reduce in resolution.  If you leave the objects at the height required for the lower LOD level (tile size of 1m) they may be clipped or vanished entirely beneath the surface when that patch reaches a tile size of 8m or 16m as you move away from it.

There are three approaches I can think of to solve that but I don't know which one I should go for or if you guys might know of something even better.

1. Don't lower the patch resolution beyond a certain tile size if the patch has certain objects on it.
   1. Easy to implement
   2. Probably makes the point of terrain LODs redundant as nearly every patch can't go beyond a certain LOD
2. Use the tessellation shader to tessellate the areas of the terrain around certain objects based on a mask, keeping the tile size at that area no bigger than the object footprint.
   1. Fast to run
   2. Won't know how good it looks until implemented
   3. Hard to implement
3. Adjust each object's height to a height picked at the lower patch resolution when that patch changes.
   1. Easy to implement
   2. Player will see objects pop to new heights in distance

 

This is mostly for my voxel terrain but it pretty much applies to all terrain I think.

Hopefully some of you might have some input or some better ideas.