Houdini 20.5 Nodes Geometry nodes

Crowd MotionPath Layer geometry node

Layers additional animation clips onto an agent’s motion path.

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Since 20.0

This SOP layers additional animation clips on top of the agent’s base animation clip. The layered clips can be applied to a subset of the agent’s skeleton. This is useful for introducing variations into a crowd shot, such as adding clips with upper body motion on top of a walk cycle.

See SOP motion paths for more information on the SOP Crowds MotionPath toolset.

Parameters

Group

The motion paths that the layered animation clip is applied to.

Trigger

Trigger Group

For each motion path, the layered clip is applied starting at the first point along the path in this group, and continues playing until the next point that is not in the trigger group.

Tip

The Crowd MotionPath Trigger SOP can be used to create many common types of triggers.

Combine Triggers

Combines the trigger with other existing triggers using boolean operations.

Boolean Operation (left drop-down box)

The boolean operation to perform (Union (Or), Intersect (And), Exclusive Or, or Subtraction).

Comparison (middle drop-down box)

Specifies whether to the perform the boolean operation on the trigger groups in the right drop-down box (With), or on all the trigger groups except those in the right drop-down box (With All But).

Trigger Group (right drop-down box)

A trigger or list of trigger group names.

Random Delay

Max Random Delay

When Random Delay is turned on, this is the maximum delay (in seconds) between when the trigger evaluates to true and when the layered clip begins. This is useful to avoid having many agents start the layered clip at the same time.

Random Seed

When Random Delay is turned on, this is the seed that is used when selecting a random delay time.

Number of Loops

When turned on, plays the layered clip for the specified number of loops, instead of playing until the trigger is no longer active. This is useful for adding a layered animation for a short period of time without needing to edit the trigger group.

Blend In Frames

When the trigger is activated, the clip is blended in over the specified number of frames.

Blend Out Frames

When the trigger is released, the clip is blended out over the specified number of frames.

Clips

Blend Mode

Specifies the blend mode to use for the layer.

Interpolate

Interpolates between the base pose and the clip’s pose according to the Blend Ratio.

Additive

Applies a percentage of the clip’s rotations and translations to the base pose, as specified by the Blend Ratio. Typically the layered clip is a difference clip, where the channels contain the difference from a reference pose rather than the actual pose. This is useful for adding additional variation while preserving the characteristics of the base animation.

Blend Ratio

Specifies how to blend between this clip and the base layer. When Blend Mode is set to Interpolate, a value of 0 has no effect, and a value of 1 completely overrides the base layer. When Blend Mode is set to Additive, Blend Ratio specifies the percentage of the clip’s rotations that are added to the base layer.

Transform Group

The name of a transform group, which specifies a subset of the transforms in the agent’s rig that the clip is applied to. Transform groups can be created using the Agent Transform Group SOP.

Randomize Clips

When turned on, selects the agent’s clip from a weighted random distribution of clips. If Use Clip Transition Graph is turned on, clips are only considered if they can be reached through a sequence of transitions from the agent’s current clip.

Random Seed

The seed for randomly selecting clips when there are multiple Clip Groups, or when Clip Names is a list of clip names.

This parameter is available when Randomize Clips is turned on.

Clip Groups

A weighted random distribution of clips to transition agents to.

This parameter is available when Randomize Clips is turned on.

Clip Names

A string pattern that specifies one or more clip names. The pattern follows the same syntax as the match VEX function. The Weight value for the group is divided evenly between the matching clips.

This parameter is available when Randomize Clips is turned on.

Weight

Specifies how likely the clips are to be selected.

This parameter is available when Randomize Clips is turned on.

Clip Name

When Randomize Clips is turned off, this is the name of the clip to transition to.

Initial Clip Time

When turned on, sets the initial clip time (in the Clip Time Units, relative to the clip’s start time) for all agents in the group.

When turned off, the initial clip time is inherited from the base animation clip when the layered clip is triggered.

Clip Time Units

This drop-down menu specifies the units of the Initial Clip Time and Random Clip Offset.

Seconds

The clip time is specified in seconds, relative to the clip’s start time.

Phase

The clip time is specified as a normalized phase, where 0 is the beginning of the clip, and 1 is the end of the clip. This can be simpler to use when working with clips of different lengths.

Random Clip Offset

When Initial Clip Time is turned on, this randomly shifts the initial clip time forward for each agent by up to the specified number of seconds.

Clip Offset Seed

When Random Clip Offset is turned on, this seed is used when randomly varying clip times.

Clip Speed

A multiplier for how fast the animation clip is played back.

When turned off, the clip speed is inherited from the base animation clip.

Clip Speed Mode

This drop-down menu controls whether the clip speed is randomized or overridden by a point attribute on the input agents.

Set Uniform

Each agent’s clip speed is set to the Clip Speed.

Set Varying

Each agent’s clip speed is randomized according to the Variance (%) and Variance Seed.

Use Attribute

Each agent’s clip speed is set from a point attribute on the input geometry.

Variance (%)

When the Clip Speed Mode is set to Set Varying, this is the percentage that the Clip Speed can be randomly increased or decreased by. For example, if the Clip Speed is 0.7 and the Variance is 10%, the agents' clip speeds will be random values between 0.63 and 0.77.

Variance Seed

When the Clip Speed Mode is set to Set Varying, this seed is used when randomly varying clip speeds.

Clip Speed Attribute

When the Clip Speed Mode is set to Use Attribute, this is the name of a float point attribute to set the clip speed from.

Inputs

Motion Paths

Polyline curves representing the paths of the agents over a time range.

Agents

A crowd of agents whose motion is represented by the Motion Paths.

Outputs

Motion Paths

Polyline curves representing the paths of the agents over a time range.

Agents

A crowd of agents whose motion is represented by the Motion Paths.

Examples

MotionPathLayerClip

This example demonstrates how to use the Crowd MotionPath Layer SOP to layer a clip onto the upper body of an agent. The clip is activated when the agent is inside a bounding object.

See also

Geometry nodes