Meshmixer is mainly about meshes. But in the 3D viewport, you will find several other types of objects.
Pivots
Pivots are persistent objects in the scene that allow you to store a "frame" - 3 orthogonal axes and a 3D location. You can select and move Pivots, and many tools can use pivots in different ways. The image below shows the three states of pivots. A Yellow pivot means that it is a "free" pivot, while an Orange pivot is "bound" to an object, and will move with it. See the Create Pivot tool for more information on this.
Complexes
A Complex is a special kind of mesh that was added in Meshmixer 3.0. The main difference is that a complex contains internal "sheets" of mesh, which join with the surface mesh at edge loops. Complex meshes are non-manifold, which means that some editing operations won't work on them. The image below shows an example. On a complex, the non-manifold edge loops are highlighted in green. With the X-Ray shader, you can see the interior structure.
Much more information about complexes is available in the topics Generate Complex Tool and Complex Tools.
Target Mesh
Some of our tools can use anther a second mesh as a "target" object. To set the currently-selected mesh as the active Target, you can either use the Set as Target/Clear Target items under the Actions menu, or use the ` and ~ hotkeys to set/clear. By default the Target object is rendered in semi-transparent blue, although if you prefer you can change it to be solid by un-checking Transparent Target in the View menu. The Target state is also reflected in the Object Browser topic. The image below shows a sphere set as the Target object, before and after use of the Attract To Target tool.
