How to use a mesh as a sprite mask

I’m generating a mesh to use as 2D terrain which can be changed to show destruction. I’d like to instantiate a “scorch mark” sprite where an explosion happens but have it only show up on the terrain.


Essentially, I’d like to use the terrain mesh instead of a sprite in a sprite mask. How can I do something like this?

I set up a second camera rendering to a texture and then added a second texture slot to my terrain shader for this texture. I just instantiate the explosion sprite in front of the second camera and it will only show up on the terrain: