Rewritable Buffers without using Compute Shaders

Unity Engine
1

Is it possible for a shader that isn’t a compute shader to have some kind of means of reading and writing data? I want to implement GPU sculpting where a mesh can be formed iteratively. A regular vertex and frag shader will not be able to remember the last frame’s vertex positions.

I would love to use compute shaders to do this, but I need to support Mac OSX.

2

Isnt it better to alter the actual mesh object instead of using a shader?

3

Modifying a mesh via regular scripting seems to be too slow for what I want - hence the desire to do this on the GPU.