Simple way to retain standard lighting model when using custom vertex/fragment shader?

We’ve written a custom vertex shader for a particular effect we need. But of course, objects using this shader now do not interact with the unity standard lighting (don’t cast or receive light/shadow).

I’d like to ask what the simplest way would be to keep this lighting model, while still using our custom shader for the objects that need it. Something like ‘chaining’ the standard and custom shaders would be great, but I don’t think that’s possible.

Is it a case of digging onto the standard shader source, and trying to copy/paste the bits we need?

Thank you.

There is no way to arbitrarily combine the functionality of two shaders other than by combining the relevant parts of their shader source code. You can download an archive containing the source of all the built-in shaders from the unity download site and use that as a base on which to add your own custom functionality.