# The Compound Node

Maya Node Type → DG Node
Maya Node Name → mvUsdCompoundShape

Multiverse allows you to efficiently stream in Maya any USD data (as well as Alembic) by encapsulating their contents into Multiverse Compounds (nodes of type mvUsdCompoundShape). No actual geometry actually exists in Maya, and Maya files remain lightweight, open quickly and operate at fast FPS in the viewport for manipulation operations, overrides and playback.

The result of a Multiverse Read operation on the shelf, is the creation of a Multiverse "Compound" node encapsulating the content of the file(s) being read.

Compound nodes can be re-arranged int the Outliner to form any hierarchy by using Maya transform nodes, then the whole hierarchy of Compounds can be written out as a Composition. You have options to selectively specify how the Compound should be written: as a "usd reference" or as a "usd payload" (aka a delayed reference). See Write Composition.

TIP

Reading is also available through the Multiverse Python API:

multiverse.CreateUsdCompound

See the relative API documentation

# Layering

You can read data in Compounds as multiple layers, the result being always the "composition" of all layers. When sparse overrides on matching hierarchy are present, the layers will be composed in a top-down fashion, with the top layers winning on the bottom ones.

As an example, here's what a typical animated character may be composed of in terms of layers:

(top)
---------------------------
[x] - chara_attrib_over.usd  // override write:       material overrides by shot
[x] - chara_attrib_over.usd  // override write:       attribute overrides by shot
[x] - chara_materials.usd    // override write:       assignment of maya or usd materials from lookdev
[x] - chara_anim.usd         // asset write (sparse): animated points from animation
[x] - chara_uv.usd           // asset write (sparse): UVs from modeling / lookdev
[x] - chara_model.usd        // asset write:          t-pose model topology from modeling
---------------------------
(bottom)

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As of Multiverse 7, it is possible to write material shading networks in USD files for either interchange purpose or rendering (3Delight NSI only). These materials can be assigned as overrides in MEOW and are identified by the blue color (while green is reserved for assignment to material shading networks stored in Maya).

Layers can be optionally muted using each layers' own check-box in the UI: note that muted layers are not written when writing compounds into larger compositions.

Note

Note that Compounds will remember all their overrides even if the layers are removed from the UI, so even if the Compound is empty from any layer.

Continue reading about layering in the dedicated Layering documentation.

# Draw Mode

The Draw mode allows you to strategically choose how to draw each individual compound for better drawing performance in the viewport. The draw mode can also be chosen before reading an asset both from the UI and from the Python API. This allows you to overcome viewport limitations with very complex assets.

Additionally you have two fine grain controls:

Instance Draw Mode: choose a different draw mode for instances
Instance Draw Ratio: choose the % ration of how many instances to draw

# USD Purpose

USD Purposes allows to selectively display render, proxy and guides primitives which were written as such by Multiverse Asset Write or by another USD toolset such as Solaris in Houdini.

By default USD primitives are tagged with the default purpose, in such case they are displayed in the Hydra render delegates, such as Storm and NSI, and they will be rendered procedurally by all of the Multiverse supported renderers.

In case render, proxy and guides primitives exist, you can selectively enable/disable them for display in the viewport. Note that proxy and guides are never rendered, while render obviously is rendered.

# Time Control

It is possible to re-time, offset and in general control the timing of the data contained in a Compound using the timing controls.

Timing controls applies to all layers.

Note

When consolidating compounds into Compositions, please note that not all timing controls can be encoded in USD, this is because USD itself does not yet have support for them:

Timing Control	Exists in
Time	Maya
Asset Time	Maya and USD
User Time	Maya
Speed Multiplier	Maya and USD
Frame Offset Time	Maya and USD
Before User Time	Maya
After User Time	Maya

# Render Control

This section offers controls for scaling the velocities (for velocity and acceleration-based motion blur), the and the points / curves size without the need to rewrite those quantities. These are very useful with FX data typically coming from Houdini and Solaris.

It is also possible to disable embedded USD materials for the whole compound, this will effectively ignore USD materials and their assignments to primitives.

# Rendering Extension Attributes

Extension attributes are available for each of the supported renderers and are automatically added to the Compound when each renderer's translator plugin for Maya is loaded.

# Render Stats

Maya "Render Stats" visibility attributes are added by Maya to the Compound.

# Reference

Section	Parameter	Description
Layers	Layer Enable/Disable	Whether a layer is enabled or disabled.
	Layer Name	The filename of the USD layer.
	Asset Path	The relative or absolute path to the asset.
	Add Layer [button]	Adds a layer.
	Remove Layer [button]	Removes a layer.
	Move Up Layer [button]	Removes a layer.
	Move Down Layer [button]	Removes a layer.
	Merge All USD Layers [button]	Pops up the Write USD Composition UI to merge into a single composition all Layers. On writing the Composition will be auto-synced into the compound and the content refreshed.
	Reload All [button]	Reload all layers.
Draw Mode	Smooth Shaded	Draw as smooth shaded.
	Maya	Use the Maya material assigned to the compound.
	USD Preview	Draw as smooth shaded with USD preview materials (if any).
	Auto Color	Use a flat color set randomly assigned to primitives.
	Point Cloud	Draw as point cloud.
	Bounding Box	Draw as bounding box.
	Bounding Boxes	Draw as multiple bounding boxes.
	Skip	Skip the display draw.
	Proxies - DEPRECATED	This mode is deprecated.
Instance Draw Mode	Inherit	Draw instances and point instances using the main draw mode.
	Point Cloud	Draw instances and point instances as point clouds.
	Bounding Box	Draw instances and point instances as bounding box.
Instance Draw Ratio	100 (%)	Jow many instances and point instances to draw in percentage.
Display Purpose	Proxy	Display USD primitives set as "proxy".
	Render	Display USD primitives set as "render".
	Guide	Display USD primitives set as "guide".
Write Mode	As Reference	When writing a “composition”, write this compound as a USD reference.
	As Delayed Reference ("payload”)	When writing a “composition”, write this compound as a USD payload (aka “delayed reference”).
Time Control	Time	The actual time of this asset.
	Asset Time (Starts/End)	The actual start and end times for this asset.
	User Time	The user time for this asset, typically is set to the same value of asset time, or a section of it.
	Speed Multiplier	Re-timing option to speed up or slow down your asset animation.
	Frame Offset time	Offset the start time of the asset animation.
	Before User Time	Behavior before the start of the user time. Note that this information is not written to USD as it does not yet exist in USD itself.
	After User Time	Behavior after the end of the user time. Note that this information is not written to USD as it does not yet exist in USD itself.
Render Control	Velocity Scale	Scale the velocity attribute of this asset, used for velocity blur or acceleration blur.
	Point Scale	Scale the point size values, will effectively make points larger or smaller.
	Curve Scale	Scale the curve control point size values, will effectively make curves thicker or thinner.
	Scale Mode	Whether you should “scale” or explicitly “set” the above velocity/point and curve values.
	Ignore Usd Material	Ignore any Usd Shading network and assignment.
Render Stats		Control the standard Maya render Stats
Extension Attributes	3Delight	Controls the 3Delight NSI extension shape attributes.
	Arnold	Controls Arnold extension shape attributes.
	Redshift	Controls Redshift extension shape attributes.
	Renderman	Controls Renderman extension shape attributes.
	VRay	Controls Vray extension shape attributes.

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