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extComputationUtils.h
1 //
2 // Copyright 2019 Pixar
3 //
4 // Licensed under the Apache License, Version 2.0 (the "Apache License")
5 // with the following modification; you may not use this file except in
6 // compliance with the Apache License and the following modification to it:
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14 // You may obtain a copy of the Apache License at
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24 #ifndef HD_EXT_COMPUTATION_UTILS_H
25 #define HD_EXT_COMPUTATION_UTILS_H
26 
27 #include "pxr/pxr.h"
28 #include "pxr/imaging/hd/api.h"
29 #include "pxr/imaging/hd/sceneDelegate.h"
30 
31 #include "pxr/base/tf/token.h"
32 #include "pxr/base/vt/value.h"
33 
34 #include <unordered_map>
35 
36 PXR_NAMESPACE_OPEN_SCOPE
37 
38 using HdExtComputationConstPtr = HdExtComputation const *;
39 using HdExtComputationConstPtrVector = std::vector<HdExtComputationConstPtr>;
40 
41 // This class contains utility methods to allow any Hydra backend to execute
42 // CPU computations via the Hydra ExtComputation framework.
43 //
44 // Note:
45 // The computation execution happens during Rprim sync. This precludes the
46 // use of computations shared by multiple Rprims, since the chain of
47 // computations for a computation primvar is executed for each Rprim.
48 class HdExtComputationUtils {
49 public:
50  using ValueStore =
51  std::unordered_map<TfToken, VtValue, TfToken::HashFunctor>;
52 
53  // Returns a map containing the (token, value) pairs for each "computation
54  // primvar".
55  // The participating computations are ordered based on their dependency
56  // and then, the CPU kernel is executed for each computation.
57  HD_API
58  static ValueStore
59  GetComputedPrimvarValues(
60  HdExtComputationPrimvarDescriptorVector const& compPrimvars,
61  HdSceneDelegate* sceneDelegate);
62 
63  // Helper methods (these are public for testing purposes)
64  using ComputationDependencyMap =
65  std::unordered_map<HdExtComputation const *,
66  HdExtComputationConstPtrVector>;
67  // Returns true if an ordering of the computations wherein any dependencies
68  // of a given computation come before it is possible, and fills
69  // sortedComps with the ordering.
70  // Returns false otherwise.
71  // The directed graph of a computation (vertex) and its dependencies (edges)
72  // is represented via the ComputationDependencyMap.
73  HD_API
74  static bool
75  DependencySort(ComputationDependencyMap cdm,
76  HdExtComputationConstPtrVector* sortedComps);
77 
78  HD_API
79  static void
80  PrintDependencyMap(ComputationDependencyMap const& cdm);
81 };
82 
83 PXR_NAMESPACE_CLOSE_SCOPE
84 
85 #endif // HD_EXT_COMPUTATION_UTILS_H
Hydra Representation of a Client defined computation.
Adapter class providing data exchange with the client scene graph.