Houdini 19.5 Reference Windows

Global Animation Options


Frames per Second sets the rate for animation playback when Real Time playback is enabled. You generally want to set the FPS for your animation only once, and do so before you begin animating anything at all. This is because when you change the FPS, the time of the last keyframe will not match the new animation length (unless Keep Keys on Current Frames is turned on). If you want to modify your animation timing, you must do so explicitly.

The FPS rate for NTSC video is 30, for PAL video, it is 25, and for Film, it is 24.

Production Tip: If you made a mistake, you can use a Field cop with a Pushup / Pulldown operation to fix a sequence of rendered-out images and convert them to a different FPS after the fact.

FPS Apply

Applies the current frame rate (FPS) setting to your animation sequence.

Keep Keys on Current Frames

When on, if you change the frame rate (FPS), then the frame each key is attached to will be preserved. This changes the playback speed of your animation.

When off, keys at frames will change in order to preserve the timing of the your animation sequence. This maintains the playback speed of your animation.


You can re-enable the old default behavior of changing the start frame to maintain its absolute time and maintaining the absolute times of keys by setting the HOUDINI_DISABLE_FPS_MAINTAIN_FSTART environment variable to 1.

For example, if you have a key on frame 1001, a key on frame 1011, and a frame range of 1001-1020 and you double the FPS, the following would occur:



Keep Keys on Current Frames = Off & HOUDINI_DISABLE_FPS_MAINTAIN_FSTART = 1

Keys are now on frames 2001 and 2021, and the frame range 2001-2040. The absolute timing of the keys and frame range are preserved, but the frames are not.

Keep Keys on Current Frames = Off & HOUDINI_DISABLE_FPS_MAINTAIN_FSTART = 0

Keys are now on frames 1001 and 1021, and the frame range is 1001-1040. The frame start is preserved, the keys and end frame maintain their timing relative to the start frame, and the absolute timing is modified.

Keep Keys on Current Frames = On & HOUDINI_DISABLE_FPS_MAINTAIN_FSTART is ignored

Keys stay on frames 1001 and 1011, and the frame range stays at 1001-1020. The frame range is preserved, the keys maintain their current frames, and the absolute timing of the keys and the FSTART/FEND have been changed.

Start / End

The Start field displays the starting frame number of the animation sequence. By default, it contains a value of one.

The End field displays the final frame number of the animation sequence.


Applies the current Start and End frame settings to your animation sequence.

Snap Keys

Snaps all keys to integer frame boundaries. This does the equivalent of chround -a.

Restrict playback range to Start and End frames

If this option in turned on, you will only be able to set time frames within the start and end range. For example, if the range is 1-240 and you try to set the playbar to -43, it will fail. Turning this checkbox off allows you to set the time frame to any value.

Show Range Slider

If this option is turned on, the slider widget underneath the playbar for visually manipulating the playback range is displayed.

Show Audio

Overlays the current audio track on the playbar so you can see audio wave.

Show Ticks

If this option is turned on, the playbar will show ticks representing the frame numbers.

Show Keys

If this option is turned on, the keyframes in current objects show up as green marks on the playbar.

Audio Wave Scale

Allows adjustment of the audio height, when shown on the playbar.

Integer Frame Values

Houdini works with floating-point frame values ( $FF ). When enableref_win_globanimoptsd, this option confines the display of frame values to integers ( $F ). When disabled, Houdini allows you to set the current time to any value, even a fractional time that does not lie exactly on an exact frame number.


The size of a single increment in frame values. For example, entering a value of 2 here plays every second frame.

Realtime Playback

Enables realtime playback on the playbar. To control the behavior of the realtime toggle, there are two options.

Maintain realtime playback, possibly skipping frames

This option is not recommended for playback of particle simulations, which will still have to compute any skipped frames.

Play every frame, but never faster than FPS

This option is better suited for playback of particle simulations.