Simulation: separate code from node tree parsing and solver

1 files changed, 138 insertions, 0 deletions

diff --git a/source/blender/simulation/intern/simulation_solver.cc b/source/blender/simulation/intern/simulation_solver.cc
new file mode 100644
index 00000000000..289e586682e
--- /dev/null
+++ b/source/blender/simulation/intern/simulation_solver.cc
@@ -0,0 +1,138 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "simulation_solver.hh"
+
+#include "BKE_customdata.h"
+
+#include "BLI_rand.hh"
+
+namespace blender::sim {
+
+ParticleForce::~ParticleForce()
+{
+}
+
+class CustomDataAttributesRef {
+ private:
+  Vector<void *> buffers_;
+  uint size_;
+  std::unique_ptr<fn::AttributesInfo> info_;
+
+ public:
+  CustomDataAttributesRef(CustomData &custom_data, uint size)
+  {
+    fn::AttributesInfoBuilder builder;
+    for (const CustomDataLayer &layer : Span(custom_data.layers, custom_data.totlayer)) {
+      buffers_.append(layer.data);
+      switch (layer.type) {
+        case CD_PROP_INT32: {
+          builder.add<int32_t>(layer.name, 0);
+          break;
+        }
+        case CD_PROP_FLOAT3: {
+          builder.add<float3>(layer.name, {0, 0, 0});
+          break;
+        }
+      }
+    }
+    info_ = std::make_unique<fn::AttributesInfo>(builder);
+    size_ = size;
+  }
+
+  operator fn::MutableAttributesRef()
+  {
+    return fn::MutableAttributesRef(*info_, buffers_, size_);
+  }
+
+  operator fn::AttributesRef() const
+  {
+    return fn::AttributesRef(*info_, buffers_, size_);
+  }
+};
+
+static void ensure_attributes_exist(ParticleSimulationState *state)
+{
+  if (CustomData_get_layer_named(&state->attributes, CD_PROP_FLOAT3, "Position") == nullptr) {
+    CustomData_add_layer_named(
+        &state->attributes, CD_PROP_FLOAT3, CD_CALLOC, nullptr, state->tot_particles, "Position");
+  }
+  if (CustomData_get_layer_named(&state->attributes, CD_PROP_FLOAT3, "Velocity") == nullptr) {
+    CustomData_add_layer_named(
+        &state->attributes, CD_PROP_FLOAT3, CD_CALLOC, nullptr, state->tot_particles, "Velocity");
+  }
+  if (CustomData_get_layer_named(&state->attributes, CD_PROP_INT32, "ID") == nullptr) {
+    CustomData_add_layer_named(
+        &state->attributes, CD_PROP_INT32, CD_CALLOC, nullptr, state->tot_particles, "ID");
+  }
+}
+
+void initialize_simulation_states(Simulation &simulation,
+                                  Depsgraph &UNUSED(depsgraph),
+                                  const SimulationInfluences &UNUSED(influences))
+{
+  RandomNumberGenerator rng;
+
+  LISTBASE_FOREACH (ParticleSimulationState *, state, &simulation.states) {
+    state->tot_particles = 1000;
+    CustomData_realloc(&state->attributes, state->tot_particles);
+    ensure_attributes_exist(state);
+
+    CustomDataAttributesRef custom_data_attributes{state->attributes, (uint)state->tot_particles};
+
+    fn::MutableAttributesRef attributes = custom_data_attributes;
+    MutableSpan<float3> positions = attributes.get<float3>("Position");
+    MutableSpan<float3> velocities = attributes.get<float3>("Velocity");
+    MutableSpan<int32_t> ids = attributes.get<int32_t>("ID");
+
+    for (uint i : positions.index_range()) {
+      positions[i] = {i / 100.0f, 0, 0};
+      velocities[i] = {0, rng.get_float() - 0.5f, rng.get_float() - 0.5f};
+      ids[i] = i;
+    }
+  }
+}
+
+void solve_simulation_time_step(Simulation &simulation,
+                                Depsgraph &UNUSED(depsgraph),
+                                const SimulationInfluences &influences,
+                                float time_step)
+{
+  LISTBASE_FOREACH (ParticleSimulationState *, state, &simulation.states) {
+    ensure_attributes_exist(state);
+
+    CustomDataAttributesRef custom_data_attributes{state->attributes, (uint)state->tot_particles};
+
+    fn::MutableAttributesRef attributes = custom_data_attributes;
+    MutableSpan<float3> positions = attributes.get<float3>("Position");
+    MutableSpan<float3> velocities = attributes.get<float3>("Velocity");
+
+    Array<float3> force_vectors{(uint)state->tot_particles, {0, 0, 0}};
+    const Vector<const ParticleForce *> *forces = influences.particle_forces.lookup_ptr(state);
+    if (forces != nullptr) {
+      for (const ParticleForce *force : *forces) {
+        force->add_force(attributes, force_vectors);
+      }
+    }
+
+    for (uint i : positions.index_range()) {
+      velocities[i] += force_vectors[i] * time_step;
+      positions[i] += velocities[i] * time_step;
+    }
+  }
+}
+
+}  // namespace blender::sim