Shadows and reflections on an invisible object

[parashutt]

Hi all. I'm just getting started in Houdini and this is my first scene and I've been working on it for two months now. Now I've got to the lighting and shadows and I can't solve the problem with the light in my scene. It seems that the solution should be obvious, but I do not understand in which direction I should move.
How to cast shadows and light (from the explosion) into the background? Do I understand correctly that you need to create a surface and create a shader for it? Or is it done in another way?
If this is done with a shader, then how to create a shader in such a way that the object becomes invisible, but casts shadows and reflections?

Edited September 13, 2022 by parashutt

[doc]

If you are using mantra you'll want to look at phantom objects in your mantra rop. If you are in Solaris I think LPE's are the way to go

Edited September 15, 2022 by doc

[parashutt]

On 15.09.2022 at 23:05, doc said:

Если вы используете мантру, вам нужно смотреть на фантомные объекты в вашей мантре. Если вы находитесь в Solaris, я думаю, что LPE - это то, что вам нужно.

If I make an object phantom, then it just disappears along with the shadows and reflection.
If I understand correctly, then phantom objects cast a shadow on other objects, but are not visible themselves. I need a little another.