I'm confused about tessellation. All the docs state that the maximum tessellation for a quad is 64 which effectively increases a 2-triangle quad into 64x64x2 triangles consistently across the original patch/quad. What I've seen online though is dynamic/localised tessellation where particular areas of the quad can be tessellated more than others, sometimes by using a grayscale texture or something similar. I've also seen distance-based demos where it looks like tessellation happens gradually at a particular distance from the camera - so you effectively end up with a round area of tessellation around the camera.

Does anyone know how this can be done?

Just twigged this. I was thinking that you only draw a single quad when tessellating but you can also draw a large grid using triangles and tessellate each triangle based on the control points’ positions.

RobMadison said:

you can also draw a large grid using triangles and tessellate each triangle based on the control points’ positions.

Yes, that is typically how it's done - the vertex shader gets the distance and passes it on to the tessellation control stage, one place or the other, it's decided what the resulting tessellation level will be.