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====== UseParentSpace for Spawners using Relative Position and Scale ======

This is a follow-on from [[en:tutorials:objects:useparentspace|UseParentSpace for Relative Object Positioning and Scaling]].

In the same way that child Objects can use the ''UseParentSpace'' property to operate within a Parent's relative position and scale... spawners can benefit from the same functionality.

{{page>snippets:init_new_project&nofooter&noeditbutton}}


===== Objects and Spawners =====

In general when specifying what object to spawn, the object is given co-ordinates in world space like:

    Position = (35, 100, 0.0)
	
With relative positioning, the object that is spawned will be positioned relative to the Parent Object's Size (The Parent Object is one that has a spawner attached).

That can be confusing. Let's view it as a tree:

  * Main Object
    * Spawner connected
      * Object to Spawn

It is the Object to Spawn, that will use the ''UseParentSpace'' property.

But before we get there, let's set up a spawner in the usual way using world coordinates.


===== Making it rain =====

Start by making a rain cloud that spawns raindrops. Here's a cloud for you to use:

<WRAP center round box 90%>
{{ tutorials:spawners:cloud.png?nolink |}}	
</WRAP>


	

Define a ''Cloud'' object in config:

<code ini>
[Cloud]
Spawner  = RainSpawner
Pivot    = center
Graphic  = @
Texture  = cloud.png
Position = (0.0, -200.0, -0.1)
</code>

Then change the ''Object'' to ''Cloud'' in the create line in the code:

<code c>
orxObject_CreateFromConfig("Cloud");
</code>

This will create a cloud object a little up from the centre of the screen. We haven't provided a spawner yet so it doesn't do anything. So define both the spawner and object to spawn with:

<code ini>
[RainSpawner]
Object           = RainDrop
TotalObject      = 0
ActiveObject     = 1000
WaveSize         = 5
WaveDelay        = 0.016 ~ 0.03
ObjectSpeed      = (0, 800)
Rotation         = 22.5
UseRelativeSpeed = true

[RainDrop]
Graphic        = @
Texture        = pixel
Size           = (1,20) ~ (1,40)
Alpha          = 0.3 ~ 0.8
Color          = (255,255,255)
Pivot          = top
AutoScroll     = both
DepthScale     = true
LifeTime       = 1.0
Smoothing      = true
Position       = (-50.0, 00.0, 0.0) ~ (90.0, 00.0, 0.5)
</code>

In the spawner config above, we're making ''RainSpawner'' spawn ''RainDrop'' objects, lots of them, in a fast down direction, but rotating the spawner by 22 degrees (plus using relative speed) to get a nice down-left direction for the rain.

For the ''RainDrop'' objects themselves, we vary their alpha transparency, stretched size and their starting position on screen between X = -50.0 to 90.0.

There is no image for the raindrops, we're just using a stretched pixel. That will do nicely. 

{{ tutorials:spawners:raining.png?nolink |}}


===== Relative Spawner Positioning =====

The last step is to convert the positioning to be relative to the Cloud's size. This means changing the ''Position'' property of the ''RainDrop'' and setting ''UseParentSpace'' to position:

<code ini>
[RainDrop]
Graphic        = @
Texture        = pixel
Scale          = (1,20) ~ (1,40)
Alpha          = 0.3 ~ 0.8
Color          = (255,255,255)
Pivot          = top
AutoScroll     = both
DepthScale     = true
LifeTime       = 1.0
Smoothing      = true
Rotation       = 22.5
Position       = (-0.3, 0.0, 0.0) ~ (0.45, 0.0, 0.5)
UseParentSpace = position
</code> 

Because the pivot of the ''Cloud'' is centred, the coordinate range is (-0.5, -0.5) to (0.5, 0.5). I've adjusted the X positions to between -0.3 and 0.45 to bring the positions in a little to work nicer with the cloud itself.

The result should be the same:

{{ tutorials:spawners:raining.png?nolink |}}


==== Further information ====
  - Ordered List Item[[en:tutorials:objects:useparentspace|UseParentSpace for Relative Object Positioning and Scaling]]
  - [[en:orx:config:settings_structure:orxobject|Object Configuration]]
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