materialOverrideResolvingSceneIndex.h

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//
// Copyright 2024 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_IMAGING_HDSI_MATERIAL_OVERRIDE_RESOLVING_SCENE_INDEX_H
#define PXR_IMAGING_HDSI_MATERIAL_OVERRIDE_RESOLVING_SCENE_INDEX_H

#include "pxr/base/tf/declarePtrs.h"
#include "pxr/imaging/hd/filteringSceneIndex.h"
#include "pxr/imaging/hdsi/api.h"

PXR_NAMESPACE_OPEN_SCOPE

TF_DECLARE_WEAK_AND_REF_PTRS(HdsiMaterialOverrideResolvingSceneIndex);

/*
HdsiMaterialOverrideResolvingSceneIndex applies material overrides if both
overrides and interface mappings are found.

The overrides for a particular 'publicUIName' are specified at path like this:

materialOverride.interfaceValues.<publicUIName>.value 
    -> overrideValueDataSource

The 'overrideValueDataSource' is copied over a network node parameter's original
'valueDataSource' at paths like this:

material.<renderContext>.nodes.<nodePath>.parameters.<inputName>.value
    -> valueDataSource

The scene index identifies which network node parameter to override by using
the 'interfaceMappings' which are defined at paths like this:

material.<renderContext>.interfaceMappings.<publicUIName> 
    -> [(nodePath, inputName), (nodePath, inputName), ...]

Below is a diagram of the expected attributes needed for material overrides
on a scene index prim of type 'material':

MaterialPrim
|
+------materialOverride
|      |
|      +----interfaceValues
|           |
|           +-publicUIName
|           |   |
|           |   +---value -> overrideValueDataSource
|           |
|           +-publicUIName
|           |   |
|           |   +---value -> overrideValueDataSource
|           |
|           +-...
|
+------material
       |
       +----ri
            |
            +--nodes
            |    |
            |    +-nodePath
            |    |     |
            |    |     +-parameters
            |    |           |
            |    |           +-inputName
            |    |           |   |
            |    |           |   +-value -> valueDataSource
            |    |           |
            |    |           +-inputName
            |    |               |
            |    |               +-value -> valueDataSource
            |    |
            |    +-nodePath  
            |          |
            |          +-parameters           
            |                |
            |                +-...       
            |
            +--interfaceMappings 
            |    |
            |    +-publicUIName   
            |    |     |
            |    |     +-i0
            |    |     |  |
            |    |     |  +----nodePath  
            |    |     |  |
            |    |     |  +----inputName  
            |    |     |
            |    |     +-i1
            |    |     |  |
            |    |     |  +----nodePath  
            |    |     |  |
            |    |     |  +----inputName  
            |    |     |
            |    |     +-...
            |    |
            |    +-publicUIName 
            |    |     |
            |    |     +-i0
            |    |     |
            |    |     |       ...
            |    |     |
            |    |     +-...
            |    |
            |    +-...
            |
*/

class HdsiMaterialOverrideResolvingSceneIndex final : 
    public HdSingleInputFilteringSceneIndexBase
{
public:
    static HdsiMaterialOverrideResolvingSceneIndexRefPtr New(
        const HdSceneIndexBaseRefPtr &inputScene)
    {
        return TfCreateRefPtr(
            new HdsiMaterialOverrideResolvingSceneIndex(inputScene));
    }

    // HdSceneIndexBase overrides
    HDSI_API 
    HdSceneIndexPrim GetPrim(const SdfPath &primPath) const override;

    HDSI_API
    SdfPathVector GetChildPrimPaths(const SdfPath &primPath) const override;

protected:

    HDSI_API
    HdsiMaterialOverrideResolvingSceneIndex(
        const HdSceneIndexBaseRefPtr &inputScene);

    // HdSingleInputFilteringSceneIndexBase overrides
    void _PrimsAdded(
        const HdSceneIndexBase &sender,
        const HdSceneIndexObserver::AddedPrimEntries &entries) override;

    void _PrimsRemoved(
        const HdSceneIndexBase &sender,
        const HdSceneIndexObserver::RemovedPrimEntries &entries) override;

    void _PrimsDirtied(
        const HdSceneIndexBase &sender,
        const HdSceneIndexObserver::DirtiedPrimEntries &entries) override;
};

PXR_NAMESPACE_CLOSE_SCOPE

#endif // PXR_IMAGING_HDSI_MATERIAL_OVERRIDE_RESOLVING_SCENE_INDEX_H