Hi,
I have a working tessellation shader but am not getting the results I hoped for. The shader works Ok but the visual effect is problematic. I base my tessellation factor on a distance from the viewer and can see the new triangles being created as I move around my model. However the generated vertexes also get destroyed as I move to higher tessellation factors and this causes some horrible visual effects. I had hoped to google up a tessellation factor which would add vertexes, but not remove previously generated ones, but I can't find anything that describes it.
In a naieve manual tessellation scheme I would subdivide my control points into triangles, then get the centroid and subdivide again (my triangles are all quad based so this would give a reasonably even distribution of roughly equalateral triangles). Each step of further subdivision would build on the previous one and no generated vertexes are lost as I make the model more detailed.
The hardware tessellator doesnt attempt this scheme - it retriangulates my control point interior in a mathematically correct way to achieve the best number of even triangles - but in doing so it does not attempt to preserve or build on the previous tessellation output.
Is there a way to achieve a steady tessellation along the naieve lines I describe ? Is it just a matter of controlling my tessellation factors "manually" (having a set of known values which achieve my expected results) rather than allowing the tessellation factor to be calculated entirely based on distance ?
Thanks,
Phillip.
