1 files changed, 138 insertions, 0 deletions
diff --git a/source/blender/simulations/bparticles/event_interface.hpp b/source/blender/simulations/bparticles/event_interface.hpp
new file mode 100644
index 00000000000..de46f85bf94
--- /dev/null
+++ b/source/blender/simulations/bparticles/event_interface.hpp
@@ -0,0 +1,138 @@
+#pragma once
+
+#include "BLI_index_mask.h"
+
+#include "block_step_data.hpp"
+#include "particle_allocator.hpp"
+
+namespace BParticles {
+
+using BLI::IndexMask;
+
+/**
+ * Interface between the Event->filter() function and the core simulation code.
+ */
+class EventFilterInterface : public BlockStepDataAccess {
+ private:
+  IndexMask m_mask;
+  ArrayRef<float> m_known_min_time_factors;
+
+  Vector<uint> &m_filtered_pindices;
+  Vector<float> &m_filtered_time_factors;
+
+ public:
+  EventFilterInterface(BlockStepData &step_data,
+                       IndexMask mask,
+                       ArrayRef<float> known_min_time_factors,
+                       Vector<uint> &r_filtered_pindices,
+                       Vector<float> &r_filtered_time_factors)
+      : BlockStepDataAccess(step_data),
+        m_mask(mask),
+        m_known_min_time_factors(known_min_time_factors),
+        m_filtered_pindices(r_filtered_pindices),
+        m_filtered_time_factors(r_filtered_time_factors)
+  {
+  }
+
+  /**
+   * Return the indices that should be checked.
+   */
+  IndexMask mask()
+  {
+    return m_mask;
+  }
+
+  /**
+   * Mark a particle as triggered by the event at a specific point in time.
+   * Note: The index must increase between consecutive calls to this function.
+   */
+  void trigger_particle(uint pindex, float time_factor)
+  {
+    BLI_assert(0.0f <= time_factor && time_factor <= 1.0f);
+
+    if (time_factor <= m_known_min_time_factors[pindex]) {
+      m_filtered_pindices.append(pindex);
+      m_filtered_time_factors.append(time_factor);
+    }
+  }
+};
+
+/**
+ * Interface between the Event->execute() function and the core simulation code.
+ */
+class EventExecuteInterface : public BlockStepDataAccess {
+ private:
+  ArrayRef<uint> m_pindices;
+  ArrayRef<float> m_current_times;
+  ParticleAllocator &m_particle_allocator;
+
+ public:
+  EventExecuteInterface(BlockStepData &step_data,
+                        ArrayRef<uint> pindices,
+                        ArrayRef<float> current_times,
+                        ParticleAllocator &particle_allocator)
+      : BlockStepDataAccess(step_data),
+        m_pindices(pindices),
+        m_current_times(current_times),
+        m_particle_allocator(particle_allocator)
+  {
+  }
+
+  ~EventExecuteInterface() = default;
+
+  /**
+   * Access the indices that should be modified by this event.
+   */
+  ArrayRef<uint> pindices()
+  {
+    return m_pindices;
+  }
+
+  /**
+   * Get the time at which every particle is modified by this event.
+   */
+  ArrayRef<float> current_times()
+  {
+    return m_current_times;
+  }
+
+  ParticleAllocator &particle_allocator()
+  {
+    return m_particle_allocator;
+  }
+};
+
+/**
+ * An event consists of two parts.
+ *   1. Filter the particles that trigger the event within a specific time span.
+ *   2. Modify the particles that were triggered.
+ *
+ * In some cases it is necessary to pass data from the filter to the execute function (e.g. the
+ * normal of the surface at a collision point). So that is supported as well. Currently, only
+ * POD (plain-old-data / simple C structs) can be used.
+ */
+class Event {
+ public:
+  virtual ~Event()
+  {
+  }
+
+  /**
+   * Gets a set of particles and checks which of those trigger the event.
+   */
+  virtual void filter(EventFilterInterface &interface) = 0;
+
+  /**
+   * Gets a set of particles that trigger this event and can do the following operations:
+   *   - Change any attribute of the particles.
+   *   - Change the remaining integrated attribute offsets of the particles.
+   *   - Kill the particles.
+   *   - Spawn new particles of any type.
+   *
+   * Currently, it is not supported to change the attributes of other particles, that exist
+   * already. However, the attributes of new particles can be changed.
+   */
+  virtual void execute(EventExecuteInterface &interface) = 0;
+};
+
+}  // namespace BParticles