I was thinking of a somewhat different use case. I was thinking of a flight simulator where tessellation only occurred close to the camera, to provide the appea

I was thinking of a somewhat different use case. I was thinking of a flight simulator where tessellation only occurred close to the camera, to provide the appearance of a more detailed mesh when viewed up close. The problem is, with a quad mesh where each vertex is 20 or 30 meters apart a plane flying nap of the earth could end up clipping through the tessellated mesh but not actually collide with the non-tessellated terrain quad mesh being used for collision detection. Or worse, the player could collide with the terrain quad mesh but the tessellation makes it visually appear to have not collided with the terrain. To only two ways I see to solve this are to either not use tessellation up close, or to compute with the CPU the vertices produced by the tessellation and use that mesh for collision.