The "Gemini Man" film achieved the creation of a younger digital version of Will Smith using groundbreaking visual effects technology. Director Ang Lee and the VFX company Weta Digital captured Will Smith's full range of facial expressions using ultra-high resolution and high frame rate cameras while he performed. They then built a detailed digital model of Smith’s body and integrated it with a biomechanical skeleton system to form a digital clone. To portray the younger version, they analyzed footage and photos of Smith from his younger years and painstakingly reverse-engineered the digital model to look like a realistic 23-year-old. The result was a fully animated, 100% digital human character that matched Smith’s youthful appearance and performances in stunning realism. This process took about two years and involved over 500 visual effects artists. Unlike traditional digital de-aging, this was a full digital recreation based on motion capture of Smith’s current performance.

If the question is about the historical NASA Project Gemini, it was a 1960s U.S. spaceflight program designed to develop and test essential space travel techniques like long-duration missions, spacewalks, and spacecraft rendezvous and docking to prepare for the Apollo Moon landings. It successfully demonstrated these critical capabilities between 1965-66.

Please specify if the question concerns the "Gemini Man" film's visual effects technology or the NASA Gemini space program for complete detail.