flattenUtils.h File Reference

Utilities for flattening layer stacks into a single layer. More...

Include dependency graph for flattenUtils.h:

Go to the source code of this file.

Typedefs
using	UsdFlattenResolveAssetPathFn = std::function< std::string(const SdfLayerHandle &sourceLayer, const std::string &assetPath)>
	Callback function for overloaded version of UsdFlattenLayerStack. More...

Functions
	SDF_DECLARE_HANDLES (SdfLayer)
USD_API SdfLayerRefPtr	UsdFlattenLayerStack (const PcpLayerStackRefPtr &layerStack, const std::string &tag=std::string())
	Flatten layerStack into a single layer with the given optional tag. More...
USD_API SdfLayerRefPtr	UsdFlattenLayerStack (const PcpLayerStackRefPtr &layerStack, const UsdFlattenResolveAssetPathFn &resolveAssetPathFn, const std::string &tag=std::string())
	Flatten the layerStack into a single layer with the given optional tag and using the resolveAssetPathFn to resolve asset paths that are encountered. More...
USD_API std::string	UsdFlattenLayerStackResolveAssetPath (const SdfLayerHandle &sourceLayer, const std::string &assetPath)
	The default UsdUtilsResolvePathFn used by UsdUtilsFlattenLayerStack. More...

Detailed Description

Utilities for flattening layer stacks into a single layer.

Definition in file flattenUtils.h.

Typedef Documentation

using UsdFlattenResolveAssetPathFn = std::function<std::string( const SdfLayerHandle& sourceLayer, const std::string& assetPath)>

Callback function for overloaded version of UsdFlattenLayerStack.

The callback is given the sourceLayer and the assetPath authored in that layer. It should return the std::string that should be authored in the flattened layer.

See Also

UsdFlattenLayerStackResolveAssetPath

Definition at line 78 of file flattenUtils.h.

Function Documentation

USD_API SdfLayerRefPtr UsdFlattenLayerStack	(	const PcpLayerStackRefPtr &	layerStack,
		const std::string &	tag = std::string()
	)

Flatten layerStack into a single layer with the given optional tag.

A composed UsdStage created from this flattened layer will be the same as a composed UsdStage whose root layer stack is the original layer stack.

Unlike UsdStage::Flatten(), this function does not flatten composition arcs, such as references, payloads, inherits, specializes, or variants.

Sublayer time offsets on the sublayers will be applied to remap any time-keyed scene description, such as timeSamples and clips.

Asset paths will be resolved to absolute form, to ensure that they continue to identify the same asset from the output layer.

See Also

UsdFlattenLayerStackResolveAssetPath

A few historical scene description features cannot be flattened into a single opinion because they unfortunately encode operations that are not closed under composition. Specifically, the SdfListOp operations "add" and "reorder" cannot be flattened. Instead, "add" will be converted to "append", and "reorder" will be discarded.

USD_API SdfLayerRefPtr UsdFlattenLayerStack	(	const PcpLayerStackRefPtr &	layerStack,
		const UsdFlattenResolveAssetPathFn &	resolveAssetPathFn,
		const std::string &	tag = std::string()
	)

Flatten the layerStack into a single layer with the given optional tag and using the resolveAssetPathFn to resolve asset paths that are encountered.

This is an advanced version of the above function.

One use case for this version of the function is to flatten a layer stack that contains relative asset paths that we want to preserve as relative paths. For example:

*  /source/root.usd # sublayers a.usd and b.usd
*  /source/a.usd    # contains reference to ./subdir/layer.usd
*  /source/b.usd
*  /source/subdir/layer.usd
*  

We may want to generate "/dest/root.flat.usd" knowing that we will (by some other means) also be copying "/source/subdir" into "/dest/subdir". It's useful then to preserve the relative paths.

Note, only the caller knows the ultimate destination of the flattened layer. So to accomplish this, we can provide a resolveAssetPathFn callback that captures the outputDir, tests if the authored path is relative, and if so, computes a new relative path (based on where it will eventually be exported).

USD_API std::string UsdFlattenLayerStackResolveAssetPath	(	const SdfLayerHandle &	sourceLayer,
		const std::string &	assetPath
	)

The default UsdUtilsResolvePathFn used by UsdUtilsFlattenLayerStack.

For paths that the current ArResolver identifies as searchpaths or absolute paths, we return the unmodified path. However, any "Layer relative path" (see SdfComputeAssetPathRelativeToLayer) will be absolutized, because we do not know if the flattened layer's containing directory will be the same as any given source layer's in the incoming layerStack.