test/source/blender/blenkernel/BKE_simulation_state.hh

/* SPDX-FileCopyrightText: 2023 Blender Foundation
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

#pragma once

#include "BKE_geometry_set.hh"

#include "BLI_map.hh"
#include "BLI_sub_frame.hh"

namespace blender::bke::sim {

class BDataSharing;
class ModifierSimulationCache;

class SimulationStateItem {
 public:
  virtual ~SimulationStateItem() = default;
};

class GeometrySimulationStateItem : public SimulationStateItem {
 public:
  GeometrySimulationStateItem(GeometrySet geometry);
  GeometrySet geometry;
};

/**
 * References a field input/output that becomes an attribute as part of the simulation state.
 * The attribute is actually stored in a #GeometrySimulationStateItem, so this just references
 * the attribute's name.
 */
class AttributeSimulationStateItem : public SimulationStateItem {
 private:
  std::string name_;

 public:
  AttributeSimulationStateItem(std::string name) : name_(std::move(name)) {}

  StringRefNull name() const
  {
    return name_;
  }
};

/** Storage for a single value of a trivial type like `float`, `int`, etc. */
class PrimitiveSimulationStateItem : public SimulationStateItem {
 private:
  const CPPType &type_;
  void *value_;

 public:
  PrimitiveSimulationStateItem(const CPPType &type, const void *value);
  ~PrimitiveSimulationStateItem();

  const void *value() const
  {
    return value_;
  }

  const CPPType &type() const
  {
    return type_;
  }
};

class StringSimulationStateItem : public SimulationStateItem {
 private:
  std::string value_;

 public:
  StringSimulationStateItem(std::string value);

  StringRefNull value() const
  {
    return value_;
  }
};

/**
 * Storage of values for a single simulation input and output node pair.
 * Used as a cache to allow random access in time, and as an intermediate form before data is
 * baked.
 */
class SimulationZoneState {
 public:
  Map<int, std::unique_ptr<SimulationStateItem>> item_by_identifier;
};

/** Identifies a simulation zone (input and output node pair) used by a modifier. */
struct SimulationZoneID {
  /** Every node identifier in the hierarchy of compute contexts. */
  Vector<int> node_ids;

  uint64_t hash() const
  {
    return get_default_hash(this->node_ids);
  }

  friend bool operator==(const SimulationZoneID &a, const SimulationZoneID &b)
  {
    return a.node_ids == b.node_ids;
  }
};

/**
 * Stores a single frame of simulation states for all simulation zones in a modifier's node
 * hierarchy.
 */
class ModifierSimulationState {
 private:
  mutable bool bake_loaded_;

 public:
  ModifierSimulationCache *owner_;
  mutable std::mutex mutex_;
  Map<SimulationZoneID, std::unique_ptr<SimulationZoneState>> zone_states_;
  /** File path to folder containing baked meta-data. */
  std::optional<std::string> meta_path_;
  /** File path to folder containing baked data. */
  std::optional<std::string> bdata_dir_;

  const SimulationZoneState *get_zone_state(const SimulationZoneID &zone_id) const;
  SimulationZoneState &get_zone_state_for_write(const SimulationZoneID &zone_id);
  void ensure_bake_loaded() const;
};

struct ModifierSimulationStateAtFrame {
  SubFrame frame;
  ModifierSimulationState state;
};

enum class CacheState {
  /** The cache is up-to-date with the inputs. */
  Valid,
  /**
   * Nodes or input values have changed since the cache was created, i.e. the output would be
   * different if the simulation was run again.
   */
  Invalid,
  /** The cache has been baked and will not be invalidated by changing inputs. */
  Baked,
};

struct StatesAroundFrame {
  const ModifierSimulationStateAtFrame *prev = nullptr;
  const ModifierSimulationStateAtFrame *current = nullptr;
  const ModifierSimulationStateAtFrame *next = nullptr;
};

class ModifierSimulationCache {
 private:
  mutable std::mutex states_at_frames_mutex_;
  /**
   * All simulation states, sorted by frame.
   */
  Vector<std::unique_ptr<ModifierSimulationStateAtFrame>> states_at_frames_;
  /**
   * Used for baking to deduplicate arrays when writing and writing from storage. Sharing info
   * must be kept alive for multiple frames to detect if each data array's version has changed.
   */
  std::unique_ptr<BDataSharing> bdata_sharing_;

  friend ModifierSimulationState;

 public:
  CacheState cache_state_ = CacheState::Valid;
  bool failed_finding_bake_ = false;

  float last_fps_ = 0.0f;

  void try_discover_bake(StringRefNull absolute_bake_dir);

  bool has_state_at_frame(const SubFrame &frame) const;
  bool has_states() const;
  const ModifierSimulationState *get_state_at_exact_frame(const SubFrame &frame) const;
  ModifierSimulationState &get_state_at_frame_for_write(const SubFrame &frame);
  StatesAroundFrame get_states_around_frame(const SubFrame &frame) const;

  void invalidate()
  {
    cache_state_ = CacheState::Invalid;
  }

  CacheState cache_state() const
  {
    return cache_state_;
  }

  void reset();
  void clear_prev_states();
};

/**
 * Wrap simulation cache in `std::shared_ptr` so that it can be owned by evaluated modifier even if
 * the original modifier has been deleted.
 */
struct ModifierSimulationCachePtr {
  std::shared_ptr<ModifierSimulationCache> ptr;
};

}  // namespace blender::bke::sim