Skip to content
MotionAtelier

Curve editor

The graph is where you draw the Ease shape: drag knots and tangent handles to set exactly how a value travels from one key to the next.

The default Ease curve with its knots and handlesAn S-shaped curve from 0 to 1 with three knots: flat at the start, steepest at the middle knot, flat at the end. Each knot shows its tangent handles.
The default Ease curve (Sine S-Curve): three knots with their tangent handles. The marker and the dot on the right show the resulting motion: slow start, fast middle, slow end. Plotted from MotionAtelier 0.4.2's own curve code, outside Houdini. An illustration of the curve, not a screen capture.

Only Ease is edited by hand. Generated shapes (Bounce, Elastic, Wave, Noise) are drawn from their parameters; press Convert to Ease to copy one into Ease and edit it freely. See Ease.

Edit the curve

Section titled “Edit the curve”
To Do this
Select a knot Click it.
Add or remove a knot from the selection Shift+click it.
Select several knots Drag a marquee over empty graph space. Shift+drag adds to the selection.
Select all knots Ctrl+A (graph focused).
Move knots Drag a selected knot. All selected knots move together.
Shape a tangent Drag a handle end.
Drag finely Hold Shift while dragging a knot or handle: movement is scaled to one tenth.
Cancel a drag Press Esc before releasing. The curve returns to where it was.
Edit a knot numerically Double-click it. See Knot inspector.

Rules the editor keeps for you:

  • The first and last knot keep their time (0 and 1). They move in value only.
  • Interior knots never cross a neighbour. A group of knots is clamped as a whole, so its spacing is preserved.
  • A handle stays on its side of the knot and within its segment. On a smooth knot, dragging one handle turns the other to the same slope; each keeps its own length.

Toolbar

Section titled “Toolbar”

The toolbar above the graph, left to right:

Button What it does
Frame curve Fits the whole curve in view (also F).
Smooth tangents Joins the selected interior knots’ two tangents on one slope.
Break tangents Lets the selected interior knots’ two tangents move independently. The shape does not change until you drag.
Flatten tangents Gives the selected knots flat (zero-slope), smooth tangents: the motion eases in and out of them.
Flip time Plays the motion backwards while keeping the start and end values.
Flip value Mirrors the curve about the straight line between its ends. An ease-in becomes an ease-out; overshoot becomes undershoot.
Insert knot Adds a knot halfway along the segment after the selected knot (or the longest segment when nothing is selected). The shape does not change.
Delete selected knots Removes the selected interior knots (also Delete or Backspace). The first and last knot cannot be deleted.

To the right of the toolbar, three check boxes show or hide the curves drawn in the graph:

  • Output: the curve that will be committed, including Motion Stack effects.
  • Base: the curve before effects, drawn dashed when effects are active.
  • Velocity: the speed of the motion over time, as a faint overlay. See Velocity view.

Right-click menu

Section titled “Right-click menu”

Right-click in the graph for the same actions, grouped:

  • Show Velocity toggles the velocity overlay.
  • Knot: Insert Knot Here (at the time you clicked), Inspect Knot, Delete Knots.
  • Tangents: Smooth, Break, Flatten.
  • Curve: Flip Time, Flip Value, Restore Default Shape (back to Sine S-Curve), Save as Recipe….
  • View: Frame.

On a generated shape the menu offers only Convert to Ease and Show Velocity.

Knot inspector

Section titled “Knot inspector”

Double-click a knot, or choose Inspect Knot, to open the knot details at the bottom of the Motion Stack tab. Select one knot to edit it.

Field Meaning
Time Normalised time of the knot. Must lie strictly between its neighbours; the first and last knot keep their time.
Value Normalised value of the knot.
Continuity Smooth knots share one slope; Broken knots have two.
Incoming Slope / Outgoing Slope Slope of each tangent, in value per unit time. On a smooth knot the outgoing slope follows the incoming one.
Incoming Influence / Outgoing Influence Handle length as a percentage of the previous or next segment. Longer handles hold the slope for longer.

An invalid entry is refused with Not changed: <reason>.

Undo in the panel

Section titled “Undo in the panel”

Every completed edit is one local undo step, kept separately for each shape. With the graph focused:

  • Ctrl+Z undoes;
  • Ctrl+Y or Ctrl+Shift+Z redoes.

Local undo never touches the scene. To revert a commit, use Houdini’s Edit ▸ Undo; see Safety and undo.

Section titled “Related”