VFX artists explain how Rubeus Hagrid (Robbie Coltrane) was able to look like a half-giant in the Harry Potter movies. One of the visual challenges that the movies had from the beginning was how to make Hagrid look like a towering figure, not only next to Harry Potter (Daniel Radcliffe), Ron Weasley (Rupert Grint), and Hermione Granger (Emma Watson), but when standing next to older characters. While the Harry Potter books are able to rely on descriptions and readers’ imaginations, the movies needed to pull off visual tricks that would make Hagrid’s height look convincing.

https://screenrant.com/harry-potter-movies-hagrid-height-change-vfx-expert-reaction/