I am having trouble finding techniques that Nolan had used in the filming of this scene.
IIRC the movie's Blu-ray contains plenty of explanations on how the special effects were done.– BCdotWEBOct 24, 2017 at 8:15
2I'm afraid this question is little broad and unspecific. What do you mean "what technique"? What specific information or technique are you after here? Can you be a little more specific? Other than that the answer is just "He used filming techniques".– Napoleon Wilson ♦Oct 24, 2017 at 10:16
Do you mean techniques like special effects (such as, how they folded the ground) or techniques like worldbuilding (such as how they helped the viewer understand how dream world works) or storytelling (such as how they got across Ariadne's wonder/curiosity) or mood setting (such as how they made the people around her seem almost but not quite natural)? Also, if this is a homework question (e.g. a film school teacher has asked you this question), they're not banned, but you should tell us the full question and where exactly you're stuck and what you've figured out on your own.– user56reinstatemonica8Oct 24, 2017 at 11:14
Here's a very technical explanation:
Returning to the Paris environment, Ariadne demonstrates her newfound ability to control the dream world by folding the streets in on themselves to form a giant "cube city."
The Dneg vfx team, lead by CG Supervisor Dan Neal, spent a week documenting the Paris location where main unit was scheduled to shoot. Lidar VFX Services scanned all of the buildings and then delivered highly detailed data from which Dneg built a series of Parisian apartment blocks. It wasn't possible to get above the buildings, so Dneg artist Lee Tibbets sourced photographs of typical Paris rooftops to fill in the missing areas.
CG Supervisor Philippe Leprince implemented the new ptex texture mapping techniques in Dneg's RenderMan shaders to allow the CG team to avoid the laborious UV coordinate mapping that is usually associated with models of this type. The final folded streets featured fully animated cars and people; anything that's not on the flat in the final images is CG.
The same quote can be found in this article, which contains additional information on the Paris scenes.