Key Tools

The Key Tools tab (the second tab on the right) holds ten actions that work directly on the keys selected in Houdini. They do not use the curve in the graph.

Try it liveOpen full screenScreenshot from Houdini. Try it live swaps in a simulation: the shipped MotionAtelier engine running in your browser (about 13 MB, loaded once), with an HTML copy of the panel and a simulated Houdini scene.

Use a tool

1. Select keys in a Channel Editor or the playbar.
2. Open the Key Tools tab and press a tool.
3. If the tool has options, a dialog opens. Press OK to apply or Cancel to change nothing.

Every tool that changes keys:

• runs on every selected channel and reports skipped channels in the status line;
• is one Houdini undo step, named MotionAtelier: <tool>;
• is checked and verified like a commit, and fully rolled back on any failure. See Safety and undo.

Tools that move keys move each channel’s selected range (every key from its first to its last selected key) as one block. Keys inside the block never cross, and a move that would collide with a key outside the block skips that channel instead of overwriting anything. Neighbouring keys with automatic tangents are fixed at their current tangents so the motion outside the range does not change.

No keys selected? Key Tools then use the channels selected in the Channel Editor’s channel list (or the playbar’s), with all their keys. See Selection behavior.

Inspect

Inspect Selection

Reports what the tools would act on, without changing anything: the selection source, the number of channels, and per channel the selected and total keys, frame range, value range and segment functions, plus [locked] or [not numeric] flags. The report appears under the buttons and can be selected and copied.

Clean Up

Remove Interior Keys

Deletes every key between each channel’s first and last selected key. Needs at least two selected keys per channel.

Remove Outside Keys

Deletes every key before the first and after the last selected key.

Reduce Keys

Removes keys from each channel’s selected range while keeping the curve within a value tolerance. The first and last key of the range keep their time and value.

Option	Default	Meaning
Value Error	0.8 %	Largest allowed deviation, as a percentage of the range’s value span.
Preserve Extrema	always on	Prominent peaks and dips are always kept. Shown for information; it cannot be turned off.

The status line reports the reduction per channel. A channel is left unchanged when no smaller result stays within the tolerance. Reduce Keys only works on Bezier and linear segments.

Retime

Scale Keys

Scales each channel’s selected range in time and value.

Option	Default	Meaning
Time Scale	100 %	100 % keeps timing; 200 % doubles the duration. A negative scale reverses time. 0 % is not allowed.
Value Scale	100 %	100 % keeps values; 0 % flattens to the value pivot.
Time Pivot	Center	The time that stays fixed: First Key, Center, Playhead or Last Key. See the note below.
Value Pivot	Center	The value that stays fixed, per channel: Minimum, Center, Zero or Maximum.
Lock scales	off	Keeps Value Scale equal to Time Scale.

Reversing a range that contains value jumps is not supported.

Time Pivot with several channels

The 0.4.2 tooltip says First Key, Center and Last Key “span every selected channel”. The shipped code takes them from each channel’s own selected range, so channels with different ranges scale about different pivots. Use Playhead for one shared pivot. See Known limitations.

Offset Channels

Staggers channels: the first channel stays, the second moves by one Offset, the third by two, and so on.

Option	Default	Meaning
Offset	3 f	Frames between consecutive channels. Negative values stagger the other way.
Order	Parameter/channel order	Or Reverse. Houdini does not report the order in which you selected channels, so channels are ordered by path.

Shift Following Keys

Ripple edit: moves every unselected key after the selection by a frame Delta (default 10 f). Use it to make room after a block you lengthened, or to close a gap. A shift that would move keys onto or past the selection is refused.

Match Durations

Retimes each channel’s selected range to one shared duration.

Option	Default	Meaning
Target	Active	Active (the first selected channel in path order), Longest, Shortest, or Custom.
Anchor	Start	The point that stays fixed: Start, End or Center.
Custom	30 f	The target duration in frames, used when Target is Custom.

Snap to Playhead

Align Starts

Shifts each channel so its first selected key lands on the playhead. Relative timing within each channel is kept.

Align Ends

Shifts each channel so its last selected key lands on the playhead.

Related

• Selection behavior
• Troubleshooting: messages such as no keys after the selection.