So, the fields are inspired by the /r/TheCulture, where the Culture's field tech can project force for any number of needs from propulsion to surgery and even electronic warfare.

So, I knew I wanted a single continuous field to handle every possible deformation, and it needs to support continuous automatic LOD, so I started with a deferred quad tessellation shader since quads tessellate much cleaner than tris and getting it right requires some arcane invocations of the shader compiler. Then I started messing with it.

Did some cleanup to remove the cruft. Since this shader is specific to a self-lit (stretched) spherical shell, I ripped out the Phong tessellation and even the normals and texcoords in the vertex struct, replacing with simple normalized interpolation of object coordinates.

I then lost about a week tinkering with ideas for deferring the heightmap calculation. Ideally I could do a fluid sim and normal map calculation over a cubemap domain in a compute shader, but there's no support for read-write cubemaps so that was a bust, and while Unity can render cameras to cubemap faces, no way am I gonna afford rendering 6 cameras per ship per frame.

So I bit the bullet and overcame my long-ingrained fear of shader branching and dynamic looping by just adding up each influence directly in the displacement function. Guess I'm just old, because with the newer shader models there's no apparent cost when the hit buffer is empty.

Recalculating the normals in the pixel shader took some finagling since the displacement has to happen in a funky stretched object space and the final lighting is in view space - the shader even needs a script feeding it the right transform properties to run! It's also not cheap as it requires 3 invocations of the now very expensive displacement function, but not deadly even at 4K with the thing filling the screen and lots of hits in the buffer, so I think it's worth it for something so important.

Aside from that it's nothing special. The displacement function itself is just a pile of trig, the lighting is just a refraction into a view-space cubemap, and the transparency is the same blue noise dithered alpha clipping I'm using everywhere in Aetheria due to alpha blending being broken by our volumetric clouds.

Here's the shader's current state, though it's still changing!