New to writing shaders, please forgive any naivety in the question!
Parallax mapping in any of its ray-marchy variants (e.g. steep parallax, cone step mapping, POM) generates fake geometry on a material, generally nearly indistinguishable from real geometry and at a much higher resolution than is practical using GPU tessellation. However, the geometry created does not extend outside the initial bounds of the triangle being rendered (unlike with GPU tessellation) - so e.g. a parallax mapped sphere still has circular edges.
I'm want to try adapting a parallax shader (preferably OpenGL, any high quality variation of parallax mapping will do though I gather cone stepping is pretty much the state of the art) to write outside of the poly bounds using gl_FragDepth (and enabling conservative depth output).
This seems to be theoretically possible (see this Unity example Modifying depth when parallax mapping | Unity Community). However that post did not include any shader code and got no responses.
Is anyone aware of an existing implementation of this (with source available), or else could give me a good idea of how I should proceed with implementing it?