21st Century Rotoscope

The Hollywood Reporter details the way big bad villain in last year's Avengers: Infinity War was brought to life.,,

Thanos [is] the genocidally inclined supervillain played by Josh Brolin ...

The process of bringing Thanos to life started at Marvel, which oversaw development for the character, a brawny humanoid with purple-tinted skin. While 14 VFX houses worked on Infinity War, Digital Domain and Weta Digital in tandem continued Thanos' development and shared responsibilities for keeping his look and performance consistent throughout the film.

Before filming began, Brolin's own facial expressions — with the actor expressing everything from a wide smile to a forbidding frown — were captured by Industrial Light & Magic's high-resolution facial-scanning system, Medusa. The technology, which was developed by Disney Research in Zurich and launched a few years ago, has been used to capture roughly 130 actors. ...

On the set, Brolin wore body- and facial-capture systems to record his performance. So the other actors would have a sense of Thanos' height, Brolin sometimes wore a backpack with a pole extending above his head to provide his fellow actors with an eyeline. ...

The above proves that there is not very much, special effects-wise, under the Hollywood sun.

Because when you scrape away all the technological overlays, Thanos is basically put together in much the same way that the character Snow White was brought to life in another Disney film back 1937.

1) There is a lot of live-action reference collected. (Computer data NOW, live-action frames blown up onto paper photostats in 1937),

2) There are a lot of people (computer technicians NOW, animation artists in 1937) who take the live-action and massage the data into a different character.

The process now is higher tech, but the dynamics remain similar. In both, an actor's performance and dimensions are transformed to serve the movie in which his/her character appears. The big difference between Disney's Snow White and Disney's Avengers: Infinity Wars is that in the Marvel movie, one actor provides both the voice and performance reference, and in Snow White and the Seven Dwarfs, two actors do that.

And yeah. The technology is different. And the animators' roles on the Thor character is de-emphasized because the publicity is on Josh Brolin, not on the people working at their computers. But the transformative journeys for both of these flicks -- eighty-one years apart -- are eerily alike.