Special effects in today blockbuster movies

In todays world its a known fact that they use VFX and other special effects to create magic on screen but we rarely get a chance what it looks like before those effects are applied when thre recently released marvel film avengers :infinity war reached $1.9 at the box office many of us couldn't help but wonder how these superhero actually looked behind the scenes.

Take a look at some of the scenes from different movie.
1.game of thrones

2.the dark knight