compsci_godot_albert/_subsections/sec03/lesson-07.org

Section 03 - Lesson 07, 08 | Moving/ Removing the Gem

• Links
• Notes
  • Moving the Gem
    • get the gem to fall
      • add a script to the root node
      • attach node script dialogue
      • detaching script from node
    • life cycle of a node
      • functions
      • tree build by stages
      • how it is built
      • process functions
      • _process(delta)
      • _physics_process(delta)
    • adding code to move gem down
  • Removing the Gem
    • basic idea
    • implementation

Links

• TOC - Godot Notes
• S03:L15.07 - Moving the Gem
• S03:L15.08 - Removing the Gem

Notes

Moving the Gem

we use scripting to extend node functionality

get the gem to fall

• we need to get the Gem/Area2D node to fall

  • if we had the sprite fall, the collision2D node would stay where it was

add a script to the root node

• click on the attach new script button in the scene pane

  • 
• one script per node is the limit
• you get access to all the children nodes inside the scene.

attach node script dialogue

• Template is generally Node: Default
• some object types provide other templates with different boiler plate code

• the node we attached a script to will have a script icon next to the eye icon

  • 

detaching script from node

• sometimes you don't want a certain script attached to a node

  • for testing purposes to prevent a script from doing something
  • you want a different script, etc.
• if a script is attached, then when you select the node the "script attach button" will change from a green plus to a red x
• press the button and detach it

life cycle of a node

functions

• _ready()
• _process(delta:float)

tree build by stages

1. initialization stage

   • creation
   • function: _init_()

2. attachment stage

   • added to tree
   • function: _enter_tree()

3. finalization stage

   • node and children ready
   • function: _read()

how it is built

• every node is given an id before it gets a name
• all init functions will be called before any other stage for any other node is invoked

• similarly the attachment stage, of adding nodes to other nodes takes place before any other function in any other node is activated

  • at this point we get a name for the node

• ready tells us that the node is up and ready to go, and so are its children

  • therefore the children of the node will be set up before the parent
  • ready will be called for the children first

process functions

• invoked on all nodes
• every frame
• used to update the node each frame

• delta refers to the time that elapsed since previous call on previous frame

  • use delta to normalize things

_process(delta)

• called in main loop
• as fast as possible

_physics_process(delta)

• called in main loop
• regular interval

adding code to move gem down

• increase the y position
• all node parameters can be found in inspector (including inherited)

• position.y = position.y + speed * delta

  • speed can be anything
  • we multiply by delta to normalize it compared to the time of the previous frame

Removing the Gem

basic idea

• use the viewport rect
• find the height of the rect
• when the y position of the gem is outside the bounds remove it

implementation

• use get_viewport_rect to get the w,h
• check if position.y > rect.size.y
• use queue_free function to remove this from the queue
• set process to stop being called via set_process