Scene Layout Introduction

In this case you will get understanding of scene layout in SkyRenderer. You will learn about the scene tree and
how to create nodes in order to place geometry in 3D space. You will get a sample code with most common
functionalities related to manipulating scene nodes, scene tree and layout.

Agenda:

• Scene tree hierarchy
• SceneLayout and SceneLayoutNode
• SceneTree and SceneNode
• Example usage

Scene tree hierarchy

All elements placed in 3D space have their own transformation that specifies object's position and orientation in
3D space. For a reminder about coordinate space and object placement in the aforementioned space, check out
INTRO_CoordinateSpace tutorial.

In some cases, it is convenient to have several objects clustered into one group, and have these objects parented
to other object in order to have their transformation relative to the parent. Because of that, it is common in 3D
software to have objects stored in the tree hierarchy instead of the flat hierarchy container. In SkyRenderer, the
hierarchy of the objects on the scene with actual objects definitions is stored first in SceneLayout, then it is
moved to SceneTree upon scene setup.

SceneLayout and SceneLayoutNode

All objects are stored before setup in tree hierarchy called SceneLayout. Each node of the SceneLayout tree is
called SceneLayoutNode and in those nodes we can add new geometry. In the typical workflow, whenever we add any
object to the scene (e.g. geometry, light or camera), first we create new SceneLayoutNode for our object, then we
load the object and place it in the specific node.
Please note that if we want to place the object in already existing node, we can skip the node creation step.

SceneTree and SceneNode

After the setup methods is called on the renderer context, all information from SceneLayout is moved into
SceneTree. Based on the existing SceneLayoutNodes, the nodes called SceneNode are created. They contain copied
data from corresponding SceneLayoutNode nodes.

Example usage

Creating a SceneLayoutNode

First, let's initialize the necessary objects to create the scene:

The SceneLayout is right now empty. We can print it, it will contain only the root node called "top_node". To
see it, we will print the current state of the SceneLayout.

In order to place any object into the scene in SkyRenderer, we will need a scene node. To add the node we call
add_node method from renderer_context:

Now our plane_NUL locator node is present in the node tree hierarchy. In order to render the scene we have to add
another two nodes: node for the camera and for its target.
This time, we will create nodes with a specific location. Transformations in SceneLayoutNode is stored in
LocusDefinition and on the setup they are transformed into Locus in SceneNode, so we need to pass appropriate
LocusDefinition to add_node function:

We properly added plane geometry in created node and the camera, so now render will show our plane:

Now let's add four spheres representing coord axes to the scene. We can add a new node for this:

Render will now consist of previously added plane and 4 spheres with center in [0, 1, 0]:

Another operation commonly performed on the scene layout is duplicating the whole subtree:

All nodes in the subtree starting with coord_NUL were duplicated with a proper suffix.
We will move the subtree so that both will be visible on the render.
To get the node to perform operations on it, you can use get_node function in SceneLayout.

To remove a subtree in the SceneLayout, we can use remove_subtree method in SceneLayout.

Summary

In this section you have learnt:

• Scene Layout Tree is used in SkyRenderer to store information about scene's elements.
• There are methods enabling to access in RendererContext scene tree and perform on its elements operations like
  duplication, removal and change of transformations.