Origin vs Geometry (How to Think About It)¶
This page explains the difference between Origins, reference geometry, and actual model geometry in FreeCAD, using simple, non-technical language.
The goal is to help you understand what things are, not how FreeCAD internally tracks dependencies.
The most important idea¶
Origins provide references. Bodies create geometry.
If you understand that sentence, most FreeCAD confusion disappears.
What the Origin is¶
Each Body in FreeCAD has an Origin.
The Origin: - defines where zero is - provides X, Y, Z axes - provides XY, XZ, YZ planes - never creates printable geometry
Think of the Origin as a coordinate system or reference framework.
You build relative to it, but it never becomes part of your part.
What Origin children really are¶
Under an Origin you see: - axes - planes
These are tools, not parts.
They exist so you can: - attach sketches - align features - place geometry accurately
They are shown as “children” only because they belong to the Origin as references, not because they are pieces of the model.
What geometry is¶
Geometry is anything that: - creates a visible solid - can be exported - can be printed
Examples: - Pad - Pocket - Revolve - Torus - Fillet
Geometry lives inside a Body, not inside the Origin.
The relationship between Origin and geometry¶
A simple way to think about it:
- The Origin does not contain geometry
- Geometry does not belong to the Origin
- Geometry is defined relative to the Origin
In other words:
The Origin helps place geometry, but does not own it.
A helpful analogy¶
Think of the Origin like graph paper taped to your desk.
- You draw shapes on the grid
- The grid helps you stay aligned
- The drawing is not part of the grid
FreeCAD works the same way.
Why this matters¶
Understanding this helps you avoid common mistakes: - trying to “move” the Origin instead of the geometry - assuming deleting an Origin will delete a part - thinking planes are solid objects
Once you separate references from geometry, the model tree becomes much easier to read.
One-sentence takeaway¶
Origins define space. Bodies create parts. Geometry may use references without being their child.