Character state machine

Which actions a character can do at what time is decided by the characters state machine. It consists out of a center main state standing and a number of action-states like Fight Left or Run Forward. From the Standing-State, most other states are reached by e.g. pressing a button (e.g. run forward) and are active as long as that button is pressed.

The Standing-State can transition to the following other states:

  • Run Forward
  • Jump Backward
  • Strafe Left
  • Strafe Right
  • Draw Weapon
  • Undraw Weapon
  • Fight Forward
  • Fight Left
  • Fight Right
  • Fight Block

One of the reasons why a state-machine is needed here is for playing the transition animations: In the original game, the states described here were implicitly coded into the currently active animation of a character. For example, there is an animation for Standing and one for Run Forward. To transition between those, a Transition from Standing to Run Forward-Animation is played. While the transition-animation plays, the character is not supposed to go to other states, so that once the Forward-Button is tapped, you will need to wait for the whole transition animation to finish. This results in the character always taking a step once the forward button is tapped.

Buttons and AI

To simplify things, when talking about buttons being pressed, this will also include the AI telling the character to do a certain action. Generally speaking, the AI cannot tell a character anything to do which is not bound to a button. Buttons are easy to understand.

Priorities

Special care has to be taken when executing a state in a loop. For example, if you hold the Jump Backward-button and then also press the Run Forward-button, the character should stay in the Jump Backward-state.

States

In the following sub-states, the filled black circle denoting the start of the state chart will always be the Standing-state, while the non-filled black circle will always go back to the Standing-state.

Animation naming

There are two categories of animations for characters (and usable objects, really), which are State- and Transition-Animations. For most people the State-Animations are the more interesting ones, as they display the character being in a state such as Standing, Running, Standing with 1H-Weapon drawn, and so on. The Transition-Animations are for going from one of such states to another.

State-Animations will be always called like S_<state>, while Transition-Animations are called T_<from>_2_<to>. Examples for such animations are S_1HRUNL or T_1HRUN_2_1HRUNL.

State Animations

The animations named in the following parts are not the complete name of the animation clip. They are rather the type of animation the character should play. The final name is constructed like so:

S_<weaponmode><walkmode><kind>

Where <weaponmode> can be one of:

  • None: Empty string
  • 1h: 1H
  • 2h: 2H
  • Bow: BOW
  • CrossBow: CBOW
  • Magic: MAG
  • Fist: FIST

And <walkmode> can be one of:

  • RUN
  • WALK
  • SNEAK
  • SWIM
  • JUMP
  • WATER
  • DIVE

And <kind> is the animation named in the following state descriptions. For example, the full animation file name S_RUNL means: No weapon, Running-Walkmode with the animation which lets the character actually run forward, called L.

Note

We don’t exactly know why the actual Go Forward-Animations are called L, but it seems like the L does indeed stand for Left, since the animation starts with the left foot. In Gothic I there are actually two separate jump animations, one for jumping off the left foot and one for the right foot.

Some trivia: In earlier versions of Gothic I the character would jump with the incorrect foot, as someone mixed up the L and R. @nicode fixed that.

As an other example, the animation file name S_FISTWALKSTRAFEL would be for fist-fighting, walking and strafing left.

If an animation does not exist, first the one without a weapon mode is tried. If that doesn’t exist either, the RUN walkmode is used. And if that doesn’t exist either, we’re out of luck and can’t play any animation.

Translation Animations

To display a smooth transition between two state animations, Piranha Bytes created special transition animations for going from one state to another. To construct the name of a transition animation, you will need:

  • The State the character is currently in
  • The State the character goes to
  • The current weapon-mode

Then the name of the transition animation is constructed like so: T_<weaponmode><from>_2_<weaponmode>.

Note

I don’t think there are transitions between different weapon types as the character would always undraw the other weapon first. However, at the moment I’m not sure whether transitions for Standing to 1H-Weapon Standing exist.

Turning Animations

Turning is a bit weird as it can happen not only while standing, but also while running or strafing. However, the turning animations shall only be played while the character is standing. Therefore it makes sense to separate these two functionalities.

Note

Turning needs to be faster when a weapon is drawn. The speedup-factor actually comes from a script value, but I’m not sure which one.

Standing-Substate description

The following states can be reached from the Standing-state.

State - Run Forward

Once the Run forward-button is pressed while in the Standing-State, the following substate shall be entered:

!include ../style.iuml state "Play Transition:\nIdle to Run" as transitionToRun state "Play Transition:\nRun to Idle" as transitionToIdle transitionToRun : Play animation: ""RUN_2_RUNL"" Run : Loop animation: ""RUNL"" transitionToIdle : Play animation: ""RUNL_2_RUN"" [*] --> transitionToRun transitionToRun --> Run : Animation Done Run --> Run : While Forward-Button down Run --> transitionToIdle : Run Forward-Button no longer down transitionToIdle --> [*] : Animation Done

Fig. 2 Statechart for running forward.

While in the Run-State, turning shall be allowed but without playing an animation. Turning Left shall take precedence over turning Right.

State - Jump Backward

Once the Jump Backward-button is pressed while in the Standing-State, the following substate shall be entered:

!include ../style.iuml state "Check Keys" as CheckKeys state "Play Animation" as PlayAnimation PlayAnimation: Play Animation: ""JUMPB"" [*] -down-> PlayAnimation PlayAnimation -right-> CheckKeys : Animation finished CheckKeys -left-> PlayAnimation : Jump Back-button down CheckKeys -down-> [*] : Jump Back button up

Fig. 3 Statechart for jump backwards.

While in the PlayAnimation-State, turning shall be allowed but without playing an animation. Turning Left shall take precedence over turning Right.

State - Strafe Left

Once the Strafe Left-button is pressed while in the Standing-State, the following substate shall be entered:

!include ../style.iuml state "Strafe Left" as StrafeLeft StrafeLeft: Loop Animation: ""STRAFEL"" [*] --> StrafeLeft StrafeLeft --> StrafeLeft : While Strafe Left-button down StrafeLeft --> [*] : Strafe Left-button Up

Fig. 4 Statechart for Strafe Left.

While in the StrafeLeft-State, turning shall be allowed but without playing an animation. Turning Left shall take precedence over turning Right.

State - Strafe Right

Once the Strafe Right-button is pressed while in the Standing-State, the following substate shall be entered:

!include ../style.iuml state "Strafe Right" as StrafeRight StrafeRight: Loop Animation: ""STRAFER"" [*] --> StrafeRight StrafeRight --> StrafeRight : While Strafe Right-button down StrafeRight --> [*] : Strafe Right-button Up

Fig. 5 Statechart for Strafe Right.

While in the StrafeRight-State, turning shall be allowed but without playing an animation. Turning Left shall take precedence over turning Right.

Architecture

The character statemachine can be split into the following parts:

  • Generic state-machine module,
  • Module constructing animation names,
  • Actual character state logic (Component),
  • Character-Visual (Component),
  • Character-Animation player (Component).