GTA: The Trilogy combines Unreal Engine with old RenderWare, machine learning helped with upscaling
Rockstar Games producer Rich Rosado gave a big
GTA producer also gave an explanation on new characters' look, somewhat different from the original design.
Developers also worked on characters with Rockstar North, including some of the original artists. Rosado compared NPCs and characters from the originals with Michelin Man. He said their bodies were separated into chunks.
Updated games work on two different engines running parallel with each other. The visuals is covered by Unreal Engine 4. But the scripts and everything else is still based on old RenderWare from the original titles.
The most difficult game to update was GTA 3. The assets in these game are too old to reuse. Some of the texture were reworked by hand, but mostly the materials were updated with machine learning.
There were also some big troubles with optimization. The team was working hard to make the games work properly on Nintendo Switch.