The Interface

Core concepts

Concept	Meaning
Design	One document: its parameters, an ordered list of features, and body metadata. Saved as a .whittle file.
Feature	One step in the design's history (a sketch, an extrude, a fillet…). Every feature can be edited later.
Sketch	A 2D drawing on a plane or on a flat face. Its closed shapes become profiles for 3D features.
Body	A solid. Features either create a new body or change an existing one.
Parameter	A named value such as width = 80 mm that any field can use in a formula.
Timeline	The row of features at the bottom. The model is rebuilt from it after every change.
Session	While a feature's panel is open, changes preview live. OK (or Enter) applies them as one undo step; Cancel (or Esc) discards them.

Parametric means: the document stores instructions, not geometry. Change a parameter or an early feature, and everything after it rebuilds automatically. Later features stay attached to the right edges and faces.

Units: the design has a length unit (mm, cm, m, in or ft). Internally everything is millimetres and radians. Plain numbers typed into a field use the design's unit (or degrees for angles).

---

The interface

┌─────────────────────────────── Title bar ───────────────────────────────┐
├──────────────────────────────── Toolbar ────────────────────────────────┤
│ Browser │                  3D viewport                     │ Properties │
│ (left)  │   context bar (top) · view cube (top right)       │  panel     │
│         │   view dock (bottom) · section card (bottom left) │ (right)    │
├──────────────────────────────── Timeline ───────────────────────────────┤
└────────────────────────────── Status bar ───────────────────────────────┘

Title bar

• File buttons: New, Open, Save, Export, then Undo and Redo (their tooltips name the step).
• Design name: click to rename. A dot shows "Saved" or "Unsaved".
• Find a command (Ctrl+K), Parameters, theme switch (Graphite dark / Paper light), Help (start screen).

Toolbar (modelling mode)

Tools are grouped. Each group label is also a menu listing every tool in that group, with a short description and shortcut.

Group	Buttons	Also in the group menu
Start	Sketch
Create	Extrude, Revolve, Loft, Hole	Import STEP / STL
Shapes	Box, Cylinder, Sphere	Cone, Torus, Tube
Modify	Fillet, Chamfer, Shell, Move / Copy	Combine, Mirror, Pattern
Inspect	Measure, Section, Print check	Display styles, Orthographic, Save image
Library	Parts
Export	Export…	Export STEP, Export 3MF, Export STL, Save image, Version history

Buttons are greyed out when they don't apply (for example, Fillet before any body exists).

Toolbar (sketch mode)

The toolbar turns orange-tinted and shows sketch tools:

Group	Tools
Draw	Line, Rectangle, Circle, Ellipse, Polygon, Slot
Special	Text, Gear, Import SVG (menu adds: Export sketch as SVG, Export sketch as DXF)
Arrange	Select, Duplicate, Mirror, Rotate 90°, Construction (menu adds: Mirror up/down, Delete)
	Finish sketch button on the right

Browser (left panel)

• Parameters: each one with its current value; click to open the Parameters dialog.
• Origin: XY, XZ and YZ planes; click one to start a sketch on it.
• Bodies: colour swatch, name, show/hide eye. Click to select; double-click to edit the feature that made it.
• Sketches: click to select, double-click or the pencil to edit. Sketches already used by a feature appear dimmed.

Properties panel (right)

Shows one of three things:

1. Feature editor while a feature is open: its fields, any warning or error with a fix button, and OK / Cancel.
2. Sketch panel while sketching: plane offset and tips, or the editor for the selected shape (sizes, solid/hole mode, construction, Arrange tools, Delete).
3. Inspector otherwise: for the whole design (features, bodies, volume, mass) or for a selected body (name, colour, finish, volume, mass, size, area), face (surface type, area) or edge (curve type, length).

Mass is calculated for a chosen material, in g or kg: plastics (PLA, PETG, ABS, nylon, SLA resin, acrylic), metals (aluminium, steel, stainless steel, brass, copper, titanium), and wood and other materials (pine, oak, plywood, MDF, glass, concrete).

Viewport overlays

Overlay	Where	Purpose
Context bar	top centre	Actions for the current selection (e.g. a face offers Sketch here, Hole, Shell, Measure)
Banner	top centre	Shown while picking a sketch plane or measuring, with Cancel / Done
View cube	top right	Click a face to look at it; home button for the default view
View dock	bottom centre	Display styles, Measure, Section, Print check, Grid, Orthographic, Fit, Save image
Section card	bottom left	Section axis, flip and position slider
Measure card	near the measured item	Measurement results
Radial menu	where you right-clicked	Up to 8 actions for what was clicked
Busy bar / loading	top / centre	Rebuild in progress / engine starting

Timeline (bottom)

One icon per feature, in order. A red or yellow dot marks an error or warning. Details in section 9.

Status bar

• Left: the hint line, which always says what to do next for the current tool or selection.
• Right: engine state ("Loading engine", "Building", "Built in N ms") and the design unit.

Command palette (Ctrl+K)

Type what you want in plain words. Every command has synonyms, so for example:

You type	It finds
"round edges"	Fillet
"hollow"	Shell
"drill", "m3", "screw"	Hole
"bolt circle"	(shape Arrange tools)
"slicer", "bambu", "prusa"	Export 3MF
"transparent"	X-ray

Arrow keys move, Enter runs, Esc closes. Only commands that apply right now are listed.

Guided first part (coach)

A step-by-step overlay that walks a new user through sketch → rectangle → extrude → fillet.