When I joined the Generation Zero team there wasn't much environment art work to be done, so I instead worked with the weapons and equipment team to create hard surface assets such as weapons, equipment gadgets and this Resistance machine companion, a.k.a PUP.
It's based on the existing "common grunt" machine enemy, which kinda resembles and acts like a dog. So the idea came about of allowing the players to override one of those machines. Which could then be customized with various modules, weapons and armour to change their utility and behaviour.
I had to use the existing model and rig and convert it into something that looked like it had been repurposed, working around the limitations of what I could change. The base version of PUP has a resistance paintjob and a few new modules, such as an attached modified radio device (cosmetic only but it allows the machine to be controlled by the player) and a default inventory module for storing items for the player.
I also created a number of different armour sets, these included protection against small-arms, explosives, and fire. As well as a "taunt" armour designed to draw attention and tank damage and also a "stealth" armour for sneaking around.
The number of modules were also expanded to include more utility such as automatic looting, healing and enemy spotting. Those additional modules seen in the trailer, including other paintjobs, were created by Joachim Persson and Rich Warner.