Centering at the Origin

Why is centering your model to the origin important? Having the model at the origin creates less confusion for customers who will likely be merging the model into another scene with other models. They will know exactly where the model will come in. Models not placed at the origin could merge into a scene and become difficult to find or edit depending on its imported position.

PSLogo For PixelSquid (2.3.1) certification, you are required to have the pivot point of the model centered on the 0, 0, 0 origin.

example of Centering at the Origin

Model Centered at Origin (model by cgeas)

example of Centering at the Origin with correct alignment

Model Properly aligned on import (plane model by 3d_molier)

things to avoid when Centering at the Origin

Model not properly oriented on import (hangar model by Giimann)

Moreover, the model must also sit on, or be slightly above the ground plane with the obvious up-axis of the model aligned with the World up-axis in your 3d application. In other words, the model should not be lying on its side, skewed in an odd direction, be upside-down or sit below the ground plane when opened.

example of Centering at the Origin

Both Orientations are Correct (models by 3DEnvironmentModels and yaschan)

NOTE
There are several object types that can have multiple valid up-axes. Things like books, pencils, crates and balls, among others can easily be aligned in different ways, and all of them can be considered correct. In these cases, the artist is allowed to choose which way they want the object to be oriented by default in the scene. But it is important that you indicate your chosen up-axis via your product imagery so a customer knows what to expect when they import your model into their scene.