Design: "Dead" Agents

[benloh]

What happens when an agent dies?

This is complicated and can vary according to agent, and the degree to which we want students to manage death via scripting vs automating it for them.

Death State

• isDead -- The state should be controlled by script, not built-in. Each agent's death will be determined by different parameters. e.g. we might set algae to isDead when its energy level goes to 0. Some agents might not die, e.g. lightbeam.

Visibility

• ghost -- For agents under input control, they should remain visible so that input controller (student) knows that they are still connected and controlling an agent.

• hidden -- Some agents need to be removed altogether. e.g. dead Algae, eaten Moths.

• visible -- Some agents need to remain visible and interactive. The costume might change to indicate the agent is dead, but other agents still need to interact with the dead agent. e.g. Dead decomposing rabbit that worms eat.

Interactivity

• inert -- Some agents should no longer interact with the environment and other agents when they are dead. This is usually true of hidden agents and ghost agents, but not necessarily true for visible agents. e.g. dead Algae cannot be eaten by fish, and should not gain energy from lightbeams, but dead rabbits can be eaten by worms. How do we implement this?

  Do we make students explicitly script the handling of dead agents? Or do we automate that? e.g. if an agent is inert do we skip any when ... touches ... or onEvent Tick updates? If students are to do any script handling of agents after they die, then it should not be handled automatically. e.g. the fish floating up after they die is handled in a onEvent Tick condition.

  There is no instruction pointer management so we can't easily introduce a keyword like break to skip code blocks.

  If agents have an inert property, we could potentially use it within the automated parts of the system, e.g. the "touches" condition can ignore agents that are inert.

Population

• Not-Removed -- Dead agents probably should not be removed from the simulation. The data needs to stick around so it can be queried. e.g. you might want to get a population count of the number of agents that died.

Implementation

How should this be implemented?

GFeature Death?

We could add a "Death" feature. The feature would add a property isDead to agents. It would be nice if we could set an inert feature property and have the scripts automatically handle updates accordingly but it gets complex quickly: e.g. if an agent is inert can we update x/y or not? Other than adding a property, the feature can't do much, so this probably not the way to go?

Custom Agent Property?

Or should we let students define the property themselves? e.g. addProp isDead Boolean false

It doesn't make sense to add it as a built-in property to GAgent because handling that property will vary according to the script? And being dead is relevant to dobject apart from the visual values?

On the other hand, it is common enough that many agents would use it?

GAgent

• agent.alpha

class-display-object

• dobj.alpha

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Use Cases

Corey's use case:

• Moth is eaten by predator
• Moth needs to be:
  • invisible during round
  • does not respond to hover
  • remain in system to be counted by population counters / graphs

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To Do

• [x] Add agent.alpha
• [x] Add dobj.alpha
• [x] Set visual alpha
• [x] Add agent.inert property
• [x] "Touches" ignores inert agents
• [x] Fish do not glow when touching dead algae
• [x] Algae do not gain energy from lightbeams when they are dead.

[benloh]

marked the checklist item Add agent.alpha as completed

[benloh]

marked the checklist item Add dobj.alpha as completed

[benloh]

marked the checklist item Set visual alpha as completed

[benloh]

marked the checklist item Add agent.inert property as completed

[benloh]

marked the checklist item "Touches" ignores inert agents as completed

[benloh]

marked the checklist item Fish do not glow when touching dead algae as completed

[benloh]

Implemented with !64