Houdini 20.0 Rendering

Creating a flipbook animation

Renders the contents of the viewer as images, allowing you to play them back at full speed.

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When you are working with complex scenes or simulations, the viewport can have trouble playing back at 24 FPS (or whatever your frame rate is). However, displaying the scene in the viewer is still faster than rendering the animation.

You can use a flipbook as a “middle ground” between playing back in the viewer and actually rendering the animation. It lets you view the OpenGL representation of the animation at full frame speed.

When you start a flipbook, Houdini plays back the animation in the viewer, but at each frame it captures the viewer content as an image. After Houdini captures each frame, you can view the images as an animation at full speed in mplay. Alternatively, you can save the images to disk to allow storing and sharing the flipbook.

How to

To...Do this

Create a new flipbook

  1. In the tools (on the left side of the viewer), right-click the Flipbook tool.

  2. Choose “Flipbook with new settings”.

  3. Use the controls in the dialog box

(If you haven’t created a flipbook before in the current session, you can just click the icon to open the dialog box.)

Recreate the previous flipbook

In the tools (on the left side of the viewer), LMB click the Flipbook tool.

Render Flipbook controls


At the top of the window Houdini prints the amount of space necessary to hold the images that will be created with the current settings.

Output tab

Frame range/inc

The start frame, end frame, and number of incremental frames to render. The default start and end frame are variable references($RFSTART and $RFEND), which grab the current values from the Houdini timeline. The menu at the right has a list of common frame ranges.

Leave Playbar at Last Frame

Instead of setting the playbar frame back to the frame it was at before the flipbook was started, leave it at the last frame the flipbook wrote.

Flipbook to MPlay

When enabled, all frames will be written to MPlay for interactive viewing.

Output Files

Allows saving of the frames to image files. Normally this is blank as frames are only written to MPlay ( Flipbook to MPlay defaults to on). If a filename is placed here, it will additionally write the frames to files as well. If __Flipbook to MPlay is off, frames will only be written to disk.

Flipbook Session Label

When Flipbook to MPlay is enabled, you can render to separate flipbooks at the same time by giving them different labels. If you use a label corresponding to an open mplay window, Houdini will send the new frames to that window.

Visible objects

Only objects whose names match this pattern will be visible in the flipbook. Use this to focus the flipbook on one or a few characters/objects.


What part of the Scene View to render to the flipbook.

Current Viewport

Render the currently selected viewport.

Current Beauty Pass

Render the beauty pass of the currently selected viewport, which excludes the background gradient, grid, handles, and decorations.

All Viewports

Render all viewports into a single image, including any viewer annotations such as messages, Draw Time, and Geometry Information.

Object Types

Which objects to include in the flipbook, by type.

Currently Visible

All object types that are currently visible will be rendered.

Geometry Objects

Only geometry objects will be rendered, which excludes bone, muscle, null, camera, light, and blend objects.

Currently Visible except Geometry

All currently visible object types except for geometry will be rendered.


All object types will be rendered.

Append frames to current flipbook

Adds the frames on to the end of the last flipbook you created, instead of starting a new flipbook. This lets you put together a flipbook of different parts of a larger animation.

Scoped channel key frames only

Only render at frames where there exists currently scoped keys.

Enable block editing

When Flipbook to MPlay is enabled`, generate a flipbook with keyframe information to enable blocking in mplay.

Initialize Simulation OPs

Reset all simulation nodes in the scene before creating the flipbook.

Flipbook tab

Use Audio Panel Settings

Use the sound file and audio offset from the Audio Panel.

Audio filename

A sound file to play during the flipbook.

Audio offset

Time (in seconds) of the audio that corresponds to the first animation frame.

Background images

When Output is ip (that is, you are rendering the flipbook into mplay), an image to show behind the flipbook animation.


When Output is ip (that is, you are rendering the flipbook into mplay), the gamma correction value to use in mPlay.


When Output is ip (that is, you are rendering the flipbook into mplay), a color look up table (LUT) file to use in mPlay.

Limit Frame Time

Progressive renderers in LOPs can take much longer to completely render than is needed for a flipbook. This optional time limit moves onto the next frame once it is hit, even if the progressive renderer is still rendering. This only applies to flipbooking LOP nodes.

Limit Frame Percent

Similar to Limit Frame Time, except the renderer progress is used as the limit. The renderer must report progress for this method to work. This only applies to flipbooking LOP nodes.



Whether to do anti-aliasing of the viewport graphics, and how much. The default uses the current setting in Houdini.

Motion Blur

Render motion blur when creating the flipbook.


When Motion blur is on, the number of subframes to use when computing the motion blur. More frames produce better results, but take longer.

The menu determines when the subframes are sampled. For any frame F


Blurs F to F+1.


Blurs F-1/2 to F+1/2.


When Motion blur is on, how long the camera shutter is open. Longer shutter time produces more blur. The default (“from camera”) uses the current camera’s setting in Houdini.

For example, if the value is 0 there is no blur. If the value is 1 there is full frame blur.


Depth of field is now performed by the viewport when looking through a camera. See hou.GeometryViewportSettings.



Reduce the size of the images as they are saved (to disk or in memory). Use this to save disk/memory space.


Specify a custom size for the flipbook images. When the checkbox is on, the flipbook uses the current viewer size.

Sheet Size

Individual frames can be collected into composite sheets when flipbooking. This parameter controls the arrangement of frames in a single sheet. The first value specifies the number of rows, while the second one controls the columns.

Crop Out View Mask Overlay

When this option is on, areas of the flipbook image outside the camera’s aspect ratio are cropped.

When this option is off, areas outside the camera’s aspect ratio are grayed out.

See also


Mantra user guide



Next steps


Other renderers