Instancing

Rationale

Having a scene and throwing nodes into it might work for small projects, but as a project grows, more and more nodes are used and it can quickly become unmanageable. To solve this, Godot allows a project to be separated in several scenes. This, however, does not work the same way as in other game engines. In fact, it’s quite different, so please do not skip this tutorial!

To recap: A scene is a collection of nodes organized as a tree, where they can have only one single node as the tree root.

../../_images/tree.png

In Godot, a scene can be created and saved to disk. As many scenes can be created and saved as desired.

../../_images/instancingpre.png

Afterwards, while editing an existing or a new scene, other scenes can be instanced as part of it:

../../_images/instancing.png

In the above picture, Scene B was added to Scene A as an instance. It may seem weird at first, but at the end of this tutorial it will make complete sense!

Instancing, step by step

To learn how to do instancing, let’s start with downloading a sample project: instancing.zip.

Unzip this scene in any place of your preference. Then, add this scene to the project manager using the ‘Import’ option:

../../_images/importproject.png

Simply browse to inside the project location and open the “engine.cfg” file. The new project will appear on the list of projects. Edit the project by using the ‘Edit’ option.

This project contains two scenes “ball.scn” and “container.scn”. The ball scene is just a ball with physics, while container scene has a nicely shaped collision, so balls can be thrown in there.

../../_images/ballscene.png ../../_images/contscene.png

Open the container scene, then select the root node:

../../_images/controot.png

Afterwards, push the ‘+’ shaped button, this is the instancing button!

../../_images/continst.png

Select the ball scene (ball.scn), the ball should appear in the origin (0,0), move it to around the center

of the scene, like this:

../../_images/continstanced.png

Press Play and Voila!

../../_images/playinst.png

The instanced ball fell to the bottom of the pit.

A little more

There can be as many instances as desired in a scene, just try instancing more balls, or duplicating them (ctrl-D or duplicate button):

../../_images/instmany.png

Then try running the scene again:

../../_images/instmanyrun.png

Cool, huh? This is how instancing works.

Editing instances

Select one of the many copies of the balls and go to the property editor. Let’s make it bounce a lot more, so look for the bounce parameter and set it to 1.0:

../../_images/instedit.png

The next it will happen is that a green “revert” button appears. When this button is present, it means we modified a property from the instanced scene to override for a specific value in this instance. Even if that property is modified in the original scene, the custom value will always overwrite it. Pressing the revert button will restore the property to the original value that came from the scene.

Conclusion

Instancing seems handy, but there is more to it than it meets the eye! The next part of the instancing tutorial should cover the rest..