Houdini 20.0 Nodes Geometry nodes

Retime geometry node

Retimes the time-dependent input geometry.

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Since 17.0

The Retime SOP provides a friendly interface for retiming its input geometry according to the given playback speed or time function. For requested times that correspond to non-integer frames of the input geometry, this operator can perform the necessary interpolation to approximate intermediate results. This is useful to control the playback speed of a cached pyro simulation.

Inputs

Input

Time-dependent geometry to retime.

Outputs

Output

Input geometry, evaluated/interpolated at the appropriate time.

Parameters

Time

Evaluation Mode

Controls how the evaluation times are computed for generating the output.

By Frame

Output corresponds to evaluation of the input geometry at the given Frame.

By Time

Output corresponds to evaluation of the input geometry at the given Time.

By Speed

Evaluation time is calculated from the specified Start Frame and playback Speed.

Shift Range

Input Frame Range is shifted to start at the specified frame.

Fit Range

Input Frame Range is uniformly expanded/contracted to the Output Frame Range.

Frame

Frame to evaluate the input at; only available when Evaluation Mode is set to By Frame.

Time

Time to evaluate the input at; only available when Evaluation Mode is set to By Time.

Start Frame

First output frame (per Output Frame Range) corresponds to evaluation of the input at this frame. Only available when Evaluation Mode is set to By Speed.

Speed

Controls the playback speed when evaluating By Speed. Pace of playback can be varied by animating this parameter.

Shift to Frame

Input Frame Range is shifted to start at this frame when Evaluation Mode is set to Shift Range.

Output Frame Range

When evaluating By Speed, playback Speed is considered inside this frame range; boundary conditions control behavior outside of the range. When Evaluation Mode is set to Fit Range, Input Frame Range is uniformly expanded or contracted to span this range.

Input Frame Range

Range of input frames. Boundary conditions are called upon if the input must be queried outside of this range.

Boundary conditions are used to control the behavior when evaluation frame falls outside of the relevant range. The conditions always apply to the Input Frame Range, but are only available for the output range when evaluating By Speed.

  • Hold: clamp evaluation to the respective range limit.

  • Extend: allow free evaluation beyond the limit.

    Note

    When evaluating By Speed, an Extend condition on the Output Frame Range will use the Speed value at that limiting frame to extrapolate outside of the range. For example, if Output Frame Range is set to 10-20 with Pre-Extend, and Speed at frame 10 is set to 5, the node will assume playback speed is 5 for all frames before 10.

  • Cycle: wrap to the other end of the range.

  • Zig-Zag: upon hitting the limit, turn around and continue.

Substeps

Number of available substeps in the input. This node interpolates between closest input samples to the desired output, taking these Substeps into account. For example, if frame 17.68 needs to be evaluated and Substeps is set to 2, input frames 17.5 and 18 will be blended to produce the result.

Add Frame Attributes

When enabled, detail attributes are added to the output geometry storing the output and input frame numbers.

Output Frame Attribute

Name of the output frame detail attribute to export when Add Frame Attributes is turned on. This attribute stores the evaluation frame after Output Frame Range and its boundary conditions are applied to it.

Input Frame Attribute

Name of the input frame detail attribute to export when Add Frame Attributes is turne don. This attribute stores the input frame number corresponding to the current output frame.

Interpolation

Interpolate Between Input Frames

Allows interpolation of input geometry from the nearest integer frames. If this option is disabled, the input is directly cooked at fractional frames.

Interpolate Rotations of Normals, Quaternion, and Transforms

Use spherical linear interpolation for smoother transitions of attributes marked as normals, quaternions, and transforms.

Interpolation

Interpolation method for blending multiple inputs.

Linear

Data will be linearly interpolated between 2 nearest frames.

Cubic

Data will be cubically interpolated between 4 input frames where possible.

Subdivision

Data will follow a cubic spline curve (based on subdivision curves) between 4 input frames where possible.

Input Timestep

Difference in time between adjacent input frames. This value is needed to correctly interpret velocities.

Use Velocity When Interpolating Position

If points have a velocity attribute (v), enabling this option cubically interpolates the point position using the velocity and quadratically interpolates the velocity. The velocity attribute is also properly scaled to account for the playback speed.

Scale Velocities

If enabled, velocities in the output are scaled to account for difference in playback speeds. This applies to the v point attribute as well as the Velocity Field if volume Blend Mode is set to Advected.

Attributes

Attributes

A space-separator list of names/patterns for attributes to linearly interpolate. Attributes that don’t match here are switched instantly when the source interpolation frames change.

Point ID Attribute

Value of this (string or integer) point attribute is used to match points, instead of the point number.

Primitive ID Attribute

Value of this (string or integer) primitive attribute is used to match primitives, instead of the primitive number.

Note

Primitive matching convention also applies to volumes and VDBs.

Volumes

Blend Mode

Specifies the method used to blend voxels of the volume or VDB primitives.

Transform Only

Volume transforms are interpolated; no blending of voxel data is performed.

By Grid Index

Voxel values are linearly interpolated; the voxels are paired by their number, so matching volumes should have the exact same dimensions and resolution.

By Voxel Position

Voxel values are linearly interpolated; the voxels are matched by their spatial position.

Advected

Voxel values are linearly interpolated along motion paths, as governed by the Velocity Field.

Velocity Field

Name of velocity field used to deduce travel paths in Advected blending mode. The referenced primitive must be a vector VDB or a triplet of scalar volumes or VDBs (whose components are suffixed with .x, .y, .z).

Advection Stepsize

Maximum timestep used for computing travel curves. Lower values of this parameter may yield better advected interpolation, at the cost of longer running times.

Interpolate Velocity Field

When Voxel Blend is set to Advected, the Velocity Field is normally left untouched. Enabling this parameter also linearly interpolates the Velocity Field.

Geometry nodes