dataSourceAttribute.h

//
// Copyright 2020 Pixar
//
// Licensed under the terms set forth in the LICENSE.txt file available at
// https://openusd.org/license.
//
#ifndef PXR_USD_IMAGING_USD_IMAGING_DATA_SOURCE_ATTRIBUTE_H
#define PXR_USD_IMAGING_USD_IMAGING_DATA_SOURCE_ATTRIBUTE_H
 
#include "pxr/usd/usd/attribute.h"
#include "pxr/usd/usd/attributeQuery.h"
#include "pxr/usdImaging/usdImaging/api.h"
#include "pxr/usdImaging/usdImaging/dataSourceStageGlobals.h"
#include "pxr/imaging/hd/dataSource.h"
#include "pxr/imaging/hd/dataSourceTypeDefs.h"
 
#include <algorithm>
 
PXR_NAMESPACE_OPEN_SCOPE
 
template <typename T>
class UsdImagingDataSourceAttribute : public HdTypedSampledDataSource<T>
{
public:
 
    HD_DECLARE_DATASOURCE(UsdImagingDataSourceAttribute<T>);
 
    VtValue GetValue(HdSampledDataSource::Time shutterOffset) override
    {
        return VtValue(GetTypedValue(shutterOffset));
    }
 
    T GetTypedValue(HdSampledDataSource::Time shutterOffset) override
    {
        // Zero-initialization for numerical types.
        T result{};
        if (!_usdAttrQuery) {
            return result;
        }
        UsdTimeCode time = _stageGlobals.GetTime();
        if (time.IsNumeric()) {
            time = UsdTimeCode(time.GetValue() + shutterOffset);
        }
 
        bool valueRetrieved = _usdAttrQuery.Get<T>(&result, time); 
        if (valueRetrieved) {
            return result;
        }
 
        // No value of expected type T could be retrieved. Try schema default
        // and if that fails return zero-initialized result.
        valueRetrieved = _usdAttrQuery.GetFallbackValue<T>(&result);
        if (valueRetrieved) {
            return result;
        }
 
        return result;
    }
 
    bool GetContributingSampleTimesForInterval(
            HdSampledDataSource::Time startTime,
            HdSampledDataSource::Time endTime,
            std::vector<HdSampledDataSource::Time> *outSampleTimes) override
    {
        if (!_usdAttrQuery) {
            return false;
        }
 
        UsdTimeCode time = _stageGlobals.GetTime();
        if (!_usdAttrQuery.ValueMightBeTimeVarying() ||
            !time.IsNumeric()) {
            return false;
        }
 
        GfInterval interval(
            time.GetValue() + startTime,
            time.GetValue() + endTime);
        std::vector<double> timeSamples;
    
        // Start with the times that fall within the interval
        _usdAttrQuery.GetTimeSamplesInInterval(interval, &timeSamples);
        // Add bracketing sample times for the leading and trailing edges of the
        // interval.
        double first, ignore, last;
        bool hasFirst, hasLast;
        // If hasFirst/hasLast comes back false for an edge, or if both the left and
        // right bracketing times for the edge are the same, it means there's no
        // bracketing sample time anywhere beyond that edge, so we fall back to the
        // interval's edge.
        _usdAttrQuery.GetBracketingTimeSamples(interval.GetMin(), &first, &ignore, &hasFirst);
        if (!hasFirst || first == ignore) {
            first = interval.GetMin();
        }
        _usdAttrQuery.GetBracketingTimeSamples(interval.GetMax(), &ignore, &last, &hasLast);
        if (!hasLast || last == ignore ) {
            last = interval.GetMax();
        }
        // Add the bracketing sample times only if they actually fall outside the
        // interval. This maintains ordering and uniqueness.
        if (timeSamples.empty() || first < timeSamples.front()) {
            timeSamples.insert(timeSamples.begin(), first);    
        }
        if (last > timeSamples.back()) {
            timeSamples.insert(timeSamples.end(), last);
        }
 
        // We need to convert the time array because usd uses double and
        // hydra (and prman) use float :/.
        outSampleTimes->resize(timeSamples.size());
        for (size_t i = 0; i < timeSamples.size(); ++i) {
            (*outSampleTimes)[i] = timeSamples[i] - time.GetValue();
        }
 
        return outSampleTimes->size() > 1;
    }
 
protected:
 
    UsdImagingDataSourceAttribute(
            const UsdAttribute &usdAttr,
            const UsdImagingDataSourceStageGlobals &stageGlobals,
            const SdfPath &sceneIndexPath = SdfPath::EmptyPath(),
            const HdDataSourceLocator &timeVaryingFlagLocator =
                    HdDataSourceLocator::EmptyLocator());
 
    UsdImagingDataSourceAttribute(
            const UsdAttributeQuery &usdAttrQuery,
            const UsdImagingDataSourceStageGlobals &stageGlobals,
            const SdfPath &sceneIndexPath = SdfPath::EmptyPath(),
            const HdDataSourceLocator &timeVaryingFlagLocator =
                    HdDataSourceLocator::EmptyLocator());
 
    UsdAttributeQuery _usdAttrQuery;
    const UsdImagingDataSourceStageGlobals &_stageGlobals;
};
 
// ----------------------------------------------------------------------------
 
 
USDIMAGING_API
HdSampledDataSourceHandle
UsdImagingDataSourceAttributeNew(
        const UsdAttribute &usdAttr,
        const UsdImagingDataSourceStageGlobals &stageGlobals,
        const SdfPath &sceneIndexPath = SdfPath::EmptyPath(),
        const HdDataSourceLocator &timeVaryingFlagLocator =
                HdDataSourceLocator::EmptyLocator());
 
USDIMAGING_API
HdSampledDataSourceHandle
UsdImagingDataSourceAttributeNew(
        const UsdAttributeQuery &usdAttrQuery,
        const UsdImagingDataSourceStageGlobals &stageGlobals,
        const SdfPath &sceneIndexPath = SdfPath::EmptyPath(),
        const HdDataSourceLocator &timeVaryingFlagLocator =
                HdDataSourceLocator::EmptyLocator());
 
// ----------------------------------------------------------------------------
 
 
template<typename T>
inline void
UsdImagingDataSourceAttribute_RecordObjectInStageGlobals(
    const UsdImagingDataSourceStageGlobals *stageGlobals,
    const SdfPath &objPath)
{
    // By default nothing to record.
}
 
template<>
inline void
UsdImagingDataSourceAttribute_RecordObjectInStageGlobals<SdfAssetPath>(
    const UsdImagingDataSourceStageGlobals *stageGlobals,
    const SdfPath &objPath)
{
    // Record asset path-valued attributes.
    stageGlobals->FlagAsAssetPathDependent(objPath);
}
 
template<typename T>
UsdImagingDataSourceAttribute<T>::UsdImagingDataSourceAttribute(
    const UsdAttribute &usdAttr,
    const UsdImagingDataSourceStageGlobals &stageGlobals,
    const SdfPath &sceneIndexPath,
    const HdDataSourceLocator &timeVaryingFlagLocator)
    : UsdImagingDataSourceAttribute(
        UsdAttributeQuery(usdAttr), stageGlobals,
        sceneIndexPath, timeVaryingFlagLocator)
{
}
 
template<typename T>
UsdImagingDataSourceAttribute<T>::UsdImagingDataSourceAttribute(
    const UsdAttributeQuery &usdAttrQuery,
    const UsdImagingDataSourceStageGlobals &stageGlobals,
    const SdfPath &sceneIndexPath,
    const HdDataSourceLocator &timeVaryingFlagLocator)
    : _usdAttrQuery(usdAttrQuery)
    , _stageGlobals(stageGlobals) 
{
    if (!timeVaryingFlagLocator.IsEmpty()) {
        if (_usdAttrQuery.ValueMightBeTimeVarying()) {
            _stageGlobals.FlagAsTimeVarying(
                    sceneIndexPath, timeVaryingFlagLocator);
        }
    }
 
    UsdImagingDataSourceAttribute_RecordObjectInStageGlobals<T>(
        &_stageGlobals, usdAttrQuery.GetAttribute().GetPath());
}
 
PXR_NAMESPACE_CLOSE_SCOPE
 
#endif // PXR_USD_IMAGING_USD_IMAGING_DATA_SOURCE_ATTRIBUTE_H