Surface Deformation

Perhaps, if its not to difficult, surface deformation of terrain or other 3D nodes (similar to that seen in Red Faction (PS2)), where a hole in a surface is created caused by an explosion/impact…

I imagine this would be quite difficult to achieve a worthwhle effect.

Thinking about it - the explosion will lower terrain in the middle - possibly raise it at the lip. You could possibly take the normals from a sphere and offset each against a smilar scaled terrain allowing for a random deviance to create the crator.

All that is left is a charred texture splat

I like your style.

I thought placing a rough sphere centered at the point of impact - and subtracting this from the intersecting terrain. Then use your lip & surface normals technique to do the rest.

Edit - the normals from a sphere are not going to be uniformed across the X and Y. - meaning they wont be a grid appearance like the terrain is.

You may want to look for which Normals of the heightmap are intersected