Working with Objects
Grouping and Ungrouping Objects
You can combine several objects into a group to treat them as a single one. For example, you might group a table with objects laying on it in order to move them together.
To group objects, select them by clicking on them while holding down Shift, and choose Arrange > Group (Cmd-G) in the menu.
To ungroup objects, select a group and choose Arrange > Ungroup (Cmd-Shift-G) in the menu.
A group of objects is represented in the Project Tree as a single item with subitems.
Nested grouping is also supported. You can group either separate objects or a group with another group. When you ungroup the bigger group, objects in a nested group will remain grouped. For example, you can group a lamp with a table. This group can then be grouped together with a chair. After ungrouping the overall group, the table with the lamp will remain grouped and the chair will be separate.
To combine objects, you can also merge them using the Arrange > Merge command.
Merged objects become one regular object. Unlike grouping, merging is irreversible. You cannot split merged objects unless you apply Edit > Undo (Cmd-Z).
You can apply the Merge command to a single object.
No matter whether one or several objects are selected, the command will merge parts of object(s) with the same material applied. Such parts will be turned into a single bigger part. The command will not change the object appearance.
Merging is effective for objects that contain identical details. For example, a 3D model of a tree can be created by duplicating the same leaf many times. This tree will be rendered faster if you merge its parts rather than group them. Merging is aslo preferred if the objects you wish to combine have the same material applied.
If there is a chance that you need to separate objects, or arrange them in different way and combine again, use grouping.