Mimic Hunt is a 4-player cooperative FPS. Mimic Hunters must identify and hunt down all the Mimics in a building, dangerous creatures possessing humans furniture and belongings.

Project duration: 5 months

Team size: 10 people (including 1 other Programmer, focusing on the player controllers and the network framework, on the team)

Engine: Unreal Engine 5

It was produced as part of the Video Games and Interactive Media master's degree at the Cnam-Enjmin (National Video Games and Interactive Media School) in Angoulême, France.

We were 2 programmers on the project, as a programmer on a student project I did a little bit of everything, but my main tasks were related to the mimics: the enemies of our game.

From furniture to mimic

We needed to have a way to quickly create mimics from furniture. Using editor scripting and special naming convention for the meshes of the .fbx files our environment artist produces, we can quickly turn a furniture divided into multiple pieces into a Mimic blueprint ready to be customized by our game designers.

A furniture starts as a single mesh, then it can get possessed by a mimic and get replaced by a brand new blueprint with several meshs representing the furniture chunks. In this state, it can shiver, answer to stimulis like the whistle etc.

Once the AI decides it's time, it awakes and turn into a moving monster, revealing organs (child actors).

Finally, it can become dead/the mimic can change furniture. In both cases, the current BP turns into a dead one, each furniture chunk is separated from the others and gets physicked.

Mimic legs

Mimic legs are independent from each other, each leg is its own actor. The tip of the leg starts in an ideal position, with a fixed distance and angle from the base of the mimic. This distance, this angle, and the overall scale of the legs are slightly randomized.

The base moves with the mimic while the tip stays in place in the world place, on each frame we apply Inverse Kinematic on the bones of the leg using Unreal's Control Rig system.

We check that the tip is not too far, and if it is we move it back into its ideal position following a "curve bell" movement that adapts to the height of the ground (if the tip goes over a step it will move up).

To avoid the leg being constantly late when the mimic is moving fast we add the mimic's current velocity vector to the tip's ideal position.

Mimic's AI and behaviors

The mimic's AI uses a behavior tree and is built around 3 states: asleep, attacking and fleeing.

Asleep: When the mimic is asleep it isn't moving. To know when it needs to awake, the mimic uses an awake score system: the awake score starts at a randomized low value, and once it reaches a threshold the mimic awakes. The threshold starts at 100 and decrease as the timer ticks.

The score can either be increased permanently by actions like the player whistling or sprinting nearby, or receive modifiers based on things like how many players or in the field of view of the mimic, how many players are looking at the mimics etc.

Once it goes over the threshold the mimic wakes up and based on its health and random numbers it either go to its attacking or fleeing state.

Attacking: When the mimic is in attack mode it will choose a player to attack based on who shot it the most, who whistled the most and who is the closest. It will then try to move to the player under a certain time limit and will either give up or reach and attach the player. Then it starts the cycle again until it tries to flee.

Fleeing: If the mimic's health or shield goes under a certain threshold the mimics scans all the furniture of the house using Unreal's Entity Query System and randomly chose one of the furniture that is furthest from all player. Being on a different floor is valued more than just being in a different room.

It goes to the new furniture and if no player is looking at it or the furniture it's targeting it destroys the current mimic and create a new one that starts in asleep mode but with the HP and shield of the old one as well as lowered health and shield thresholds.

If a player is looking at it, the health and shield thresholds are lowered and the mimic goes back to attacking.

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From furniture to mimic

Mimic legs

Mimic's AI and behaviors

Jérémy L. Auclair - Game programmer