USD : Add loading of Arnold procedural prims

Changes

@@ -1,7 +1,10 @@
 10.5.x.x (relative to 10.5.14.1)
 ========
 
+Improvements
+------------
 
+- USDScene : Added loading of ArnoldAlembic, ArnoldUsd and ArnoldProceduralCustom prims as Cortex ExternalProcedural objects.
 
 10.5.14.1 (relative to 10.5.14.0)
 =========

contrib/IECoreUSD/src/IECoreUSD/ArnoldProceduralAlgo.cpp

@@ -0,0 +1,163 @@
+//////////////////////////////////////////////////////////////////////////
+//
+//  Copyright (c) 2025, Cinesite VFX Ltd. All rights reserved.
+//
+//  Redistribution and use in source and binary forms, with or without
+//  modification, are permitted provided that the following conditions are
+//  met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//
+//     * Redistributions in binary form must reproduce the above copyright
+//       notice, this list of conditions and the following disclaimer in the
+//       documentation and/or other materials provided with the distribution.
+//
+//     * Neither the name of Image Engine Design nor the names of any
+//       other contributors to this software may be used to endorse or
+//       promote products derived from this software without specific prior
+//       written permission.
+//
+//  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+//  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+//  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+//  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+//  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+//  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+//  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+//  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+//  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+//  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+//  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//////////////////////////////////////////////////////////////////////////
+
+#include "IECoreUSD/DataAlgo.h"
+#include "IECoreUSD/ObjectAlgo.h"
+
+#include "IECoreScene/ExternalProcedural.h"
+
+IECORE_PUSH_DEFAULT_VISIBILITY
+#include "pxr/usd/usdGeom/gprim.h"
+IECORE_POP_DEFAULT_VISIBILITY
+
+using namespace IECore;
+using namespace IECoreScene;
+using namespace IECoreUSD;
+
+//////////////////////////////////////////////////////////////////////////
+// Reading
+//////////////////////////////////////////////////////////////////////////
+
+namespace
+{
+
+const pxr::TfToken g_arnold( "arnold" );
+const pxr::TfToken g_arnoldAlembic( "ArnoldAlembic" );
+const pxr::TfToken g_arnoldNodeEntry( "arnold:node_entry" );
+const pxr::TfToken g_arnoldProceduralCustom( "ArnoldProceduralCustom" );
+const pxr::TfToken g_arnoldUsd( "ArnoldUsd" );
+
+// Arnold's procedural schemas are a mishmash of parameters specific to the procedural
+// and generic Arnold-specific node parameters that have no place in USD because
+// they have USD equivalents already. There is no way of querying which is which, so
+// we manually list the ones we need to ignore.
+const std::unordered_set<std::string> g_parameterSkipList = {
+	"visibility", "sidedness", "receive_shadows", "self_shadows", "invert_normals",
+	"ray_bias", "matrix", "transform_type", "shader", "opaque", "matte", "use_light_group",
+	"light_group", "use_shadow_group", "shadow_group", "trace_sets", "motion_start", "motion_end",
+	"id", "override_nodes", "operator", "name", "node_entry"
+};
+
+IECore::ObjectPtr readArnoldProcedural( pxr::UsdGeomGprim &gprim, pxr::UsdTimeCode time, const Canceller *canceller )
+{
+	ExternalProceduralPtr result = new ExternalProcedural();
+
+	// Get procedural type.
+
+	if( gprim.GetPrim().IsA( g_arnoldAlembic ) )
+	{
+		// For historical reasonss, the "filename" is actually the Arnold node
+		// type.
+		result->setFileName( "alembic" );
+	}
+	else if( gprim.GetPrim().IsA( g_arnoldProceduralCustom ) )
+	{
+		std::string nodeEntry;
+		gprim.GetPrim().GetAttribute( g_arnoldNodeEntry ).Get( &nodeEntry, time );
+		result->setFileName( nodeEntry );
+	}
+	else if( gprim.GetPrim().IsA( g_arnoldUsd ) )
+	{
+		result->setFileName( "usd" );
+	}
+
+	// Get bound.
+
+	pxr::VtVec3fArray extent;
+	gprim.ComputeExtent( time, &extent );
+	if( extent.size() == 2 )
+	{
+		result->setBound(
+			Imath::Box3f( DataAlgo::fromUSD( extent[0] ), DataAlgo::fromUSD( extent[1] ) )
+		);
+	}
+
+	// Get parameters.
+
+	for( const auto &attribute : gprim.GetPrim().GetAuthoredAttributes() )
+	{
+		if( attribute.GetNamespace() != g_arnold )
+		{
+			continue;
+		}
+
+		const std::string parameterName = attribute.GetBaseName().GetString();
+		if( g_parameterSkipList.count( parameterName ) )
+		{
+			continue;
+		}
+
+		if( auto data = DataAlgo::fromUSD( attribute, time ) )
+		{
+			result->parameters()->writable()[parameterName] = data;
+		}
+	}
+
+	return result;
+}
+
+bool arnoldProceduralMightBeTimeVarying( pxr::UsdGeomGprim &gprim )
+{
+	if( gprim.GetExtentAttr().ValueMightBeTimeVarying() )
+	{
+		return true;
+	}
+
+	for( const auto &attribute : gprim.GetPrim().GetAuthoredAttributes() )
+	{
+		if( attribute.GetNamespace() != g_arnold )
+		{
+			continue;
+		}
+
+		const std::string parameterName = attribute.GetBaseName().GetString();
+		if( g_parameterSkipList.count( parameterName ) )
+		{
+			continue;
+		}
+
+		if( attribute.ValueMightBeTimeVarying() )
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
+ObjectAlgo::ReaderDescription<pxr::UsdGeomGprim> g_arnoldAlembicReaderDescription( g_arnoldAlembic, readArnoldProcedural, arnoldProceduralMightBeTimeVarying );
+ObjectAlgo::ReaderDescription<pxr::UsdGeomGprim> g_arnoldProceduralCustomReaderDescription( g_arnoldProceduralCustom, readArnoldProcedural, arnoldProceduralMightBeTimeVarying );
+ObjectAlgo::ReaderDescription<pxr::UsdGeomGprim> g_arnoldUsdReaderDescription( g_arnoldUsd, readArnoldProcedural, arnoldProceduralMightBeTimeVarying );
+
+} // namespace