InstanceGraph#

The InstanceGraph is instant3Dhub’s core concept to structure the data based on resources inside a 3D session. It reflects the data on a resource level as well as their internal structure for assembly resources. After adding a first resource, we will now take a look, how resources are assembled in webvis.

This tutorial will explain the InstanceGraph concept which is the central structure for many of webvis API functions.

The InstanceGraph is a hierarchical tree structure, which combines two major aspects, i.e. the logical representation of a scene graph and the semantic structure of CAD data like BOMs or assembly structures combined with the sub-assembly structures of the individual part structures.

We illustrate the InstanceGraph using an example consisting of three different 3D CAD resources. The first resource is urn:x-i3d:shape:key, which is the assembly structure of a keyboard key. It has no geometry and references the CAD parts urn:x-i3d:shape:cap and urn:x-i3d:shape:switch which contain the actual CAD geometry:

assembly structure

part structure

part structure

urn:x-i3d:shape:key

urn:x-i3d:shape:cap

urn:x-i3d:shape:switch

assembly

subassembly

subassembly1

These resources form the following structure:

tree_lessabstract

Scene Graph aspect#

All nodes are presented in a tree structure. This allows a clear and understandable presentation. Operations are applied to parts of the hierarchy. In the process these operations are applied along paths in graph. E.g. if a node is disabled, all nodes below it are also disabled.

CAD aspect#

Constructions consist of multiple parts, where each part usually corresponds to a single CAD resource. These parts are assembled by references/links in a so called assembly structure, defined through structure files (e.g. PLMXML, step242, x3d). In our example, the CAD resource urn:x-i3d:shape:key defines an assembly structure, which links the two other CAD resources, urn:x-i3d:shape:cap and urn:x-i3d:shape:switch. Especially, larger parts usually have their own sub-assembly structure as e.g. keycap is subdivided into letter and cap.

The sub-assembly structure is then inserted into the assembly structure, which results into the InstanceGraph structure.

tree2

InstanceGraph#

The InstanceGraph is the composition of all assembly structures and sub-assembly structures of the corresponding linked CAD parts. Therefore, the nodes keycap and switch function as transitions to 3D resources.

tree3

webvis creates a node for every part of the tree shown above.

nodetree

Node Types#

There are different types of nodes, where as one node can also belong to multiple node types.

  • Part Nodes These nodes contain only the geometry itself.

  • Resource Nodes webvis uses resource nodes to build a bridge between geometry and the overall structure of a model. They contain no actual geometry.

  • Runtime Nodes As their name indicates runtime nodes are added during runtime. Every node added through the API is a runtime node. In our example “key” is a runtime node as it’s been loaded dynamically during runtime. Structures like switch or letter are no runtime nodes, because they are loaded through the key itself.

    Warning

    Key is also a resource node as it contains a link to other resource nodes.

InstanceGraph operations#

Properties#

part node

resource node

runtime node

color / transparency

✔

✔

✔

transformation

✖

✔

✔

enable / disable

✔

✔

✔

pickable

✔

✔

✔

remove

✖

✔

✔

add

✖

✖

✔

Some operations can’t be applied to certain types of nodes. The table above shows, what is allowed or not.