Guest Editor's Introduction to the Special Section on I3D

The papers in this special section are extended versions of four papers from the 2017 ACM Symposium on Interactive 3D Graphics and Games (I3D), the 21st conference in a series starting in 1986. I3D 2017 was held February 25th to 27th, 2017 in San Francisco, California, USA at the Intercontinental Mark Hopkins Hotel.