Variable translation control
Translation and rotation are the two types of movement of a solid body. Almost all 3D video games include variable rotational control of a player character (mostly pitch and yaw, sometimes roll), which allows rotation in any rotational direction at any speed. However, few games also offer variable translation control, with which the user can translate a player character in any translational direction at any speed, yielding a very smooth fluid motion.
Benefits of variable translation control
Without variable translation control, only one speed is available for each axial direction, so only eight directions are possible for each 2D plane (usually the longitudinal/lateral plane) and only one speed is possible for each of those directions. This results in jerky and coarse movements. To compensate for there only being eight directions relative to the user, the user will generally have to face their avatar in a certain direction, so that one of the directions aligns with their intended travel direction; or if they are aiming at a target they may have to continuously press and let go of a movement key to zigzag along their intended travel direction.
Possible reasons for not supporting variable translation control
Video games with 3D graphics often offer only variable rotational control, without variable translation control. Here are a couple of reasons.
To avoid sliding feet
Without sophisticated animation code, an avatar’s feet will appear to slide on the ground when moving at any other speed than what the animator specifically animated for. This may have been the case with Heretic II when the game went from first person POV to third person POV. Every speed at every direction had to be manually pre-animated for. It is possible that with advanced skeletal animation code, variable translation control would not cause sliding feet. A player would need variable translation control to take full advantage of new sophisticated animation code.
To reduce network traffic
One bit per direction is less than many bits per direction when a client communicates a move to a server. With network prediction code a client sends their input data, as their future position can be calculated from this. This may have been the case with Quake III Arena when it went from singleplayer to multiplayer focused. It is possible that with network bandwidth having increased many times over the years, variable translation control could return to multiplayer games. What could be done is population based scaling. When more players come near each other, the number of bits per direction could proportionally scale down. As fewer players are near each other the number of bits per direction could scale back up. This would at least allow the player fluid motion or near fluid motion at least some of the time in multiplayer games.
PC game applications
With variable translation control
- Doom (video game) and the following games using the Doom engine
- Quake and the following games using the Quake engine
- Quake II using the Quake II engine
- Descent (video game), Descent II, Descent 3, and Forsaken (video game) (all four have six degrees of freedom)
- Duke Nukem 3D
Without variable translation control
- Heretic II
- Quake III Arena and the following games using id Tech 3
Other applications
Google Earth utilises variable translation control.
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