koobas.hobune.stream
Where do character-object interactions live?
I am working on adding selection and interaction to my game. The Selection part (for my player) is not too difficult - I'm using the raycast-from-camera method to click-select. Selectable objects have a Selectable script attached to them so I can tell whether they can be interacted with.
My question is about how people structure their code to manage this interactivity. Different objects have different actions (e.g. pick up, open, press). Different characters may be able to perform different actions. Some actions may have other constraints (e.g. need a specific key or other item).
The selection code will need to combine all of these data to determine the available actions and offer options to the player. When an action is executed, it may need to affect the object (e.g. the door opens), the character, or both (e.g. the character's inventory gets the item, the item's game object is destroyed).
I am wondering if anyone has pointers, suggestions, tutorials, etc. that help keep this manageable since it can easily become a complicated mess... Do you have some kind of separate data structure that defines all possible actions and assigns them to specific items and characters? Subclassed behavior classes that define each possible action? How do you match up the "actions item offers" with the "actions character can perform" and then execute the correct code on each end?
I don't want to keep all of this code in my player-character, because I'd like to use the core functionality for NPCs as well (just add the GUI interface for the player)...
...also, I realize that the details of things like an inventory system or NPC AI are way out of scope for this question. I am just wondering about the architecture of a selection- and action-management system that would be flexible enough to interface with other systems like an action selection GUI, or an inventory management system, or an NPC's AI depending on the situation.
Different characters may be able to perform different actions. Some actions may have other constraints
There are a number of approaches:
One method is double-dispatch http://en.wikipedia.org/wiki/Double_dispatch Using a visitor you can determine the correct set of actions based on the types of the classes.
Another method would be some kind of conditional action, which contains a delegate which evaulates to true if that action is possible. Both objects could add all of the possible actions and then you can draw the actions based on which are possible.
pseudocode:
possibleActions.add(new ConditionalAction( "Look for potion", delegate { return (player.hasPotion == false); } );
thanks, I was not familiar with the Visitor pattern before. Definitely worth looking into - I don't know if it will provide a complete solution, but it will get me on the right track.
visitor is a good alternative to RTTI, we use it at work quite a lot.
I set up my items as prefabs (doors, triggers, health etc) with scripts attached to them so it leaves my main character free from these scripts. The scripts on the prefabs just have colliders on them to check if they are interacted with by anything with the "player" tag and execute and script associated with them if the "player" conditions are met. Ideally, I'd like to set it up with a more sophisticated design pattern, but as it is now, it works just fine like this with minimal clutter.
Sorry, this does not really answer my question. Triggering "automatic" actions is pretty straightforward. $$anonymous$$y question is for situations where there may be multiple possible actions (e.g. Open door or Lock door), or when you want to give the character a choice (do you want to open the door?), or when the action affects both the "target" and the "actor" (maybe you have a single-use key that disappears after the door opens).
