- 1.1 Editing Parts and Collision Geometries Efficiently
2 Building Parts from a 3D Model
3 Creating Parts and Geometries Manually
4 Modifying the Position and Orientation of Parts
5 Performance Optimization Techniques
- 5.1 Part Sleeping
- 5.2 Part Auto-merging
6 Editing the Part's Mass Properties
- 6.1 Setting the Mass Properties in the 3D View
- 6.2 Configuring the Added Mass
7 Specifying the Initial Velocity of Parts

Parts represent rigid bodies that can be connected together with joints and can collide with each other and the environment.

For information on modeling the shapes of parts, affecting collision forces, and modeling fluid interaction forces such as buoyancy, drag, and lift, please refer to Collision Geometries.

A Part can be added to an Assembly and contains a set of Collision Geometries.

The figure below indicates where parts are located in the Vortex® hierarchy.

A part has three control types: animated, dynamic, and static. Control types dictate how the part interacts with other parts. The control type of each part can be changed in the corresponding part's Properties panel.

This table shows which control type has which effect on a Part. Is the part affected by forces, e.g., when colliding with another part? Or, can the part move at all? For example. a part reacts to forces when the Control setting is Dynamic. Forces can be applied to a part by constraints, contacts, and gravity. In this setting, the part can move.

Control Type	Can Move (has velocity)	Affected by Force	Example

Control Type	Can Move (has velocity)	Affected by Force	Example
Animated	Yes	No	Windmill blades, conveyor belt, drawbridge
Dynamic	Yes	Yes	Door on hinge, bouncing ball, articulated arm
Static	No	No	Terrain, horizontal or vertical planes

Editing Parts and Collision Geometries Efficiently

In order to make it easer to work on a part and its collision geometries, a part can be viewed in its own reference frame. For more details, see Viewing a Part in its Reference Frame

Building Parts from a 3D Model

Once you have created the assembly and added your 3D model, you can start adding parts.

This procedure assumes you have set up an assembly and imported a graphic asset from which you built the parts. If that is not the case, follow the instructions under Assemblies first.

Follow these instructions for each part you want to create:

In the Explorer Panel, expand the tree to locate the node that you want to use to generate the geometry. As you move around the tree you can see in the 3D View that various nodes on the reference model are being highlighted.
Right-click on the node and select Create Part from the context menu.
Right-click on the part in the Explorer Panel and select one of the following from the context menu:
- Create Best-Fit Geometry > Best-Fit to let Vortex® decide which primitive geometric shape fits the best.
- Create Best-Fit Geometry > <Shape Name> to pick a specific primitive geometric shape to use.
- Create Best-Fit Geometry > Triangle Mesh... to generate a triangle mesh.
- Create Best-Fit Geometry > Convex Mesh... to generate a convex mesh.
- Create Best-Fit Geometry > Convex Mesh Decomposition... to select a convex mesh decomposition method and specify its parameters.
If you chose best-fit, Vortex will select the shape that most closely approximates the 3D model from the list of primitive shapes only (convex and triangle meshes are never used). For example, in the image below, the wheel on the left at the front appears with a box collision geometry shape and the wheel on the right at the front appears with a triangle mesh. You can also see the wheel at the back which has no part or geometry at all.

You can now see the newly generated geometries in the tree. By default, they are set up for collision only, but you can change this to buoyancy or drag geometries by following the instructions under Changing the Geometry Type (Collision, Buoyancy, Drag, Lift).

Creating Parts and Geometries Manually

You can add a collision, buoyancy, and drag force geometry to your part which provides a specific set of properties.

Buoyancy and drag geometries are typically used to set fluid interaction properties when creating parts: for example, for subsea simulation environments.

Creating geometries from a 3D model at the Assembly level is by far the best option; however, sometimes you need to create parts and add geometries to them manually. In this case, you can follow the instructions in this section.

If you are not already in the Assembly editor, either create a new part or load an existing one.
From the Toolbox, drag the Part to the 3D View. A Part will be created at the drop location and it will be added to the Assembly.

You can also drag and drop the Part in the tree, or simply double-click on the Part in the Toolbox
From Toolbox, drag the desired shape type you want for the part into the 3D View, or double-click it (see Geometry Shape Types for a list and description of the available types). The Collision Geometry will be added to the selected Part. You can also double-click the Collision Geometry, or drop it in the explorer tree.
Select the part from in the Explorer panel.
In the part's Properties panel, select the Geometries tab.
Select the box for the desired collision type. (For example, Buoyancy.)

You can add multiple geometries of different types, all of which are added to the Part tree in the Explorer panel. However, you can only add up to one drag and one buoyancy geometry per part.

After you have added geometries in the 3D View grid, you can modify them by, e.g., assigning a material to the selected collision geometry, edit their shape or reposition and reorient them. Please refer to Collision Geometries for more details.

Modifying the Position and Orientation of Parts

You can choose to transform the parts in your assembly using either of these methods:

By using the Transform tools in the 3D View
By editing the values directly in the Properties panel for each part