I have a problem that has been taking me many days.
I am making some vfx, for a video game, where I have to make some explosions, I do them in Houdini.
When I want to reproduce the texture sheet in the engine (unity), I see that they come out with a strange outline. Do you know why? I can't remove it, is it because of the HDRP of Unity? or am I exporting wrong?

When i open the normal and color atlas generated, looks like this (images).

May be there is an option inside the texture sheet node that i missing??