Billboard-like shader + ShadowCaster

I'm implementing a billboard-style shader (which maps a texture always facing to the camera on any 3D object).

Imagine a sprite of a bush mapped to a sphere like this:


(I need that for lighting, and I know I can use normal maps, but this is not the case. I'm going to use this shader for quite complex objects).

Texture mapping works great, but I got troubles with shadows.

I've made my own shadowcaster pass, but the trouble is that I use unity_WorldToCamera for coords calculation and obviously that works wrong for the light lines perpendicular to the line of sight. My bush-ball looks something like this for the light perpendicular to the camera:


And I get these weird shadows.

As I see, the correct way is to use something like "unity_WorldToLight" in the shadowcaster pass, but it is not accessable during this pass. I'm even not sure if a shadowcaster pass called each time for each light source. I couldn't find any information on that.

PS: I'm using a built-in render pipeline, if that matters.

 

You want

UNITY_MATRIX_V

, which is the world to view space transform for the currently rendering view.