Hi Indigo,
I've seen symbols during smoke meditation too and they've been very meaningful to me. The first thing that your description brought to my mind was the 3rd eye chakra pic that Mydriasis posted.
The triangle in that image is a Hindu
Trikona, Greek
delta or Hebrew
deleth - all represent a
door. The cross you saw may be a symbol for Christ (if you meant a Christian type cross) who said
"I am the door".
The "3" thing, if it matches Mydriasis' pic, is the
Aum or Om -
"the name of God, the vibration of the Supreme".
If you do some research on dreams and/or spiritual communication you'll find that the language of Spirit is
symbol and
metaphor, i.e., what you saw.
I think that you, having opened the door (whether you knew that or not), had an encounter with God who, via these symbols, was communicating something to you.
Thanks for sharing your
beautiful vision!
If you want to, please let us know what meaning you draw from it.
Peace