From FreeCAD Documentation
- Select one or more mesh objects.
- There are several ways to invoke the command:
- Press the Decimation... button.
- Select the Meshes → Decimation... option from the menu.
- The Decimating task panel opens.
- Specify the Reduction:
- If only one mesh object has been selected and you choose the Absolute number option:
- Move the slider or enter a number to specify an absolute number of faces.
- In other cases:
- Move the slider or enter a number to specify a percentage of faces.
- Specify the tolerance.
- Press the OK button to finish the command.