Working with the Scene Graph

Every 3D scene in Aspose.3D for Java is organized as a tree of Node objects. Scene provides a single root — getRootNode() — and every piece of geometry, material, and transform lives under that root as a child or descendant node.

Creating the Scene and Accessing the Root Node

Scene initializes automatically with a root node named "RootNode":

import com.aspose.threed.Scene;
import com.aspose.threed.Node;

Scene scene = new Scene();
Node root = scene.getRootNode(); // always "RootNode"

Adding Child Nodes

Call createChildNode() on any node to add a child. The method has three commonly used overloads:

import com.aspose.threed.*;

Scene scene = new Scene();
Node root = scene.getRootNode();

// 1. Named node with no entity — useful as a pivot or group container
Node pivot = root.createChildNode("pivot");

// 2. Named node with an entity
Mesh mesh = new Mesh("box");
mesh.getControlPoints().add(new Vector4(0, 0, 0));
mesh.getControlPoints().add(new Vector4(1, 0, 0));
mesh.getControlPoints().add(new Vector4(1, 1, 0));
mesh.getControlPoints().add(new Vector4(0, 1, 0));
mesh.createPolygon(0, 1, 2, 3);
Node meshNode = root.createChildNode("box", mesh);

// 3. Named node with entity and material
PbrMaterial mat = new PbrMaterial("red");
mat.setAlbedo(new Vector4(0.8f, 0.2f, 0.2f, 1.0f));
Node decorated = pivot.createChildNode("red_box", mesh, mat);

To attach a node that was constructed separately, use addChildNode():

Node detached = new Node("standalone");
root.addChildNode(detached);

Querying Child Nodes

Find a direct child by name or by index, or iterate all direct children:

// By name — returns null if no direct child has that name
Node found = root.getChild("box");
if (found != null) {
    System.out.println("Found: " + found.getName());
}

// By index
Node first = root.getChild(0);

// Iterate all direct children
for (Node child : root.getChildNodes()) {
    System.out.println(child.getName());
}

getChild(String name) searches only direct children, not the full subtree. Use accept() to search the entire tree.

Traversing the Full Tree

node.accept(NodeVisitor) walks a node and all its descendants in depth-first order. The visitor returns true to continue or false to stop early:

import com.aspose.threed.NodeVisitor;

// Print every node name in the scene
scene.getRootNode().accept(n -> {
    System.out.println(n.getName());
    return true; // false would stop traversal
});

// Stop after finding the first node that has an entity
final Node[] found = {null};
scene.getRootNode().accept(n -> {
    if (n.getEntity() != null) {
        found[0] = n;
        return false; // stop walking
    }
    return true;
});

NodeVisitor is a single-method interface, so it accepts a lambda in Java 8+.

Controlling Visibility and Export Exclusion

Nodes can be hidden or excluded from export without being removed from the hierarchy:

Node ground = root.createChildNode("ground_plane", mesh);
ground.setVisible(false);       // hidden in viewport / renderer

Node helperNode = root.createChildNode("debug_arrow", mesh);
helperNode.setExcluded(true);   // omitted from all export operations

setVisible(false) is a display hint. setExcluded(true) prevents the node from appearing in exported files regardless of format.

Attaching Multiple Entities to One Node

A node has a primary entity (getEntity() / setEntity()), but can hold additional entities through addEntity(). This is useful when different mesh pieces share a single transform:

Mesh body  = new Mesh("body");
Mesh wheel = new Mesh("wheel");

Node carNode = root.createChildNode("car");
carNode.addEntity(body);
carNode.addEntity(wheel);

// Retrieve all entities on this node
for (Entity ent : carNode.getEntities()) {
    System.out.println(ent.getName());
}

Merging Nodes

merge() moves all children, entities, and materials from a source node into the target node. The source node is left empty:

Node lod0 = root.createChildNode("lod0");
lod0.createChildNode("mesh_high", mesh);

Node lod1 = root.createChildNode("lod1");
lod1.createChildNode("mesh_low", mesh);

// Consolidate lod0 children into lod1
lod1.merge(lod0);
// lod1 now has both mesh_high and mesh_low; lod0 is empty

Next Steps

Applying Transforms — position, rotate, and scale any node using its Transform
Creating and Working with Meshes — build polygon geometry and attach it to nodes

API Quick Reference

Member	Description
`scene.getRootNode()`	Root of the scene tree; always present after `new Scene()`
`node.createChildNode(name)`	Create a named child node with no entity
`node.createChildNode(name, entity)`	Create a named child node with an entity
`node.createChildNode(name, entity, material)`	Create a named child node with entity and material
`node.addChildNode(node)`	Attach a separately constructed `Node`
`node.getChild(name)`	Find a direct child by name; returns `null` if not found
`node.getChild(index)`	Get the direct child at a given index
`node.getChildNodes()`	`List<Node>` of all direct children
`node.accept(visitor)`	Walk this node and all descendants depth-first
`node.addEntity(entity)`	Attach an additional entity to the node
`node.getEntities()`	`List<Entity>` of all entities on this node
`node.setVisible(bool)`	Show or hide the node
`node.setExcluded(bool)`	Include or exclude the node from export
`node.merge(other)`	Move all children and entities from `other` into this node