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Appearance per Face

In one sentence: Assign different materials, colours, or visual appearances to individual faces of a Part shape without modifying the geometry.

Overview

Workbench: Part · Menu: Part → Appearance per Face
Toolbar: Part Analysis · Shortcut: none

Appearance per Face opens a dialog that lets you select individual faces of a shape and assign them a different material or colour. The result is a multi- coloured or multi-material visual representation, while the geometry remains a single Part shape.

Intuition

A manufactured part often has different surface treatments: a anodised aluminium body (grey), a rubber grip (black), and a polished stainless steel ring. You can model all of this as a single Part solid and then assign different appearances per face to produce an accurate visual representation without splitting the solid into separate objects.

This is a display-only operation — the geometry is not modified. The face colours are stored as view properties and appear in rendering and screenshots, but they have no effect on mass properties, Booleans, or export geometry (STEP exports the shape; colour data may or may not export depending on the format).

When to use it

  • Visualising material boundaries on a multi-material part.
  • Highlighting specific faces for documentation screenshots.
  • Colour-coding faces for analysis reviews (e.g., red = defect area).

When NOT to use it

  • Actual material assignment for simulation — use the FEM workbench's material assignment, which associates material properties (density, Young's modulus) with the volume, not just the visual face colour.
  • Splitting a solid by material — use Boolean Cut or Boolean Fragments and assign materials to separate objects.

Step-by-step walkthrough

  1. Select the Part shape in the model tree.
  2. Part → Appearance per Face.
  3. The Appearance per Face panel opens, listing all faces.
  4. Select a face (or multiple faces with Ctrl+click) in the list or viewport.
  5. Click Set Appearance and choose a colour or material.
  6. Repeat for other faces.
  7. Click OK.

Parameters

Parameter Description
Face selection Select one or more faces from the shape
Material / Colour Material preset or custom colour (diffuse, specular, emissive)
Transparency Per-face transparency (0 = opaque, 1 = fully transparent)

Python API

import FreeCAD as App
import FreeCADGui as Gui

doc = App.newDocument()
box = doc.addObject("Part::Box", "Box")
doc.recompute()

# Set colour for specific faces via the ViewObject
view_obj = Gui.ActiveDocument.getObject("Box")

# FaceColors is a list of (r, g, b, a) tuples, one per face
# Box has 6 faces (Face1–Face6)
view_obj.DiffuseColor = [
    (0.8, 0.2, 0.2, 0.0),  # Face1 — red
    (0.2, 0.8, 0.2, 0.0),  # Face2 — green
    (0.2, 0.2, 0.8, 0.0),  # Face3 — blue
    (0.8, 0.8, 0.2, 0.0),  # Face4 — yellow
    (0.8, 0.2, 0.8, 0.0),  # Face5 — magenta
    (0.2, 0.8, 0.8, 0.0),  # Face6 — cyan
]

Common mistakes and pitfalls

Per-face colours are view properties, not geometry

Per-face colours do not survive if the shape is copied with Simple Copy or passed through a Boolean operation. The new result object starts with the default colour. Re-apply per-face colours after any shape operation.

See also