Unity Tips & Tricks #1: Skating game

Sep 12, 2018

Skating game: The Beginning

One of the main incentives for starting this blog was for me to keep a trace of some of the hard-earned insights both in game programming and machine learning. Indeed, I recently found myself fighting with some recurrent problems, having forgotten the solution I came up with in a previous game prototype. In order to increase efficiency and maybe help out some others self-taught game devs, I tought blog posts could be a nice solution !

Context

While browsing Twitter and Reddit, I came across some videos promotting the game SKTBRD, currently under developpement by KevKev. The game feel really appealed me and I thought that it would be interesting to figure out how to do something similar.

My realisation

After a few hours of works, here’s what I came up with:

Skating !

The whole scene is rather basic but I was satisfied with the physics aspects.

Some insights gained

Camera

Firstly, it was in this game that I figured out the setup for nice, smooth, lerping camera.

Basically I:

  1. Update the camera’s rotation, look target in the Update method
  2. Added the code for updating the camera position in the FixedUpdate method

Skater

In the current state, the player’s rotation relies on the concatenation of two quaternions and the applied force’s vector’s rotation.

  • A first rotation that would align the player’s forward axis with the current rigidbody’s velocity. Both vector are projected on the y = 0 plane, using Vector3.ProjectOnPlane(vector, plane_normal)
  • The second rotation aligns the player’s up vector with the current ground normal. The latter is obtained via raycasting.
  • Finally, forces are rotated to match player’s input, according to camera position. This way the player rotates eventually towards this direction.

Specific stuff

  • I locked all rotations axis in the rigidbody’s definition. This prevent unwanted flips.
  • I separated airborne and grounded rotation. Indeed, I use an important speed of interpolation to nicely follow curves. This would make the skater snap when jumping, which was unsatisfying.
  • The rotation using the ground’s normal is set to the identity when airborne
  • Quaternion.FromToRotation is likely to be a good friend in this setting.

By the way, here’s the whole code.

TODO

As I said, the game physics are quite satisfying, from a realistic point of view. However, even though it seems obvious, fun (both in creating and playing the game) depends heavily how you tweak reality. I’m now aiming to

  • Allow wall riding
  • Implement the possibility of jumping and falling into the same quater
  • Allow slid