Filming starts next month for sequel to Trainspotting
Carlyle, who plays psycho Begbie in both movies, said the script for the new film is "absolutely fantastic" and stronger than the first film.
Carlyle said: "We start shooting, I understand, in the middle of May and I think it's going to be pretty much 50-50 between Edinburgh and Glasgow.
"I'm basing this on nothing other than the fact that the production office is on Bathgate. There's a clue there.
"What I will say is that all the characters are exactly where you would want them to be.
"The strength of this new script is the fact that the narrative is a bit stronger than it was in the original.
"In the first one, when you think about it, it's hard to remember what they did other than get together, the drug deal at the end, and then it's over.
"This has maybe got a wee bit more to it in terms of what they've been up to through these years.
"You learn a lot about Renton, Sick Boy and indeed Begbie and where their heads are.
"I think it's an absolutely fantastic script. John Hodge has done a wonderful job, as he did with the original.
"Fingers crossed people will take it on board and they will enjoy it."
Carlyle and Welsh said Begbie is a uniquely Scottish thug that cannot be found in their adopted homes in America.
Begbie relishes up close and personal violence, in contrast to the USA where violence is "all about the gun".