Simulation: Add modifier to access simulation data

For now the "Simulation" modifier only exists for point cloud objects, because
we need this for the particle system. Right now, the modifier is doing nothing.

There is a new `DEG_add_simulation_relation` function that is used
by the modifier to make sure that the simulation is evaluated before
the modifier is executed.

Reviewers: brecht, sergey

Differential Revision: https://developer.blender.org/D7549

4 files changed, 112 insertions, 0 deletions

diff --git a/source/blender/modifiers/CMakeLists.txt b/source/blender/modifiers/CMakeLists.txt
index 48acbdc17f3..8ab7d35070b 100644
--- a/source/blender/modifiers/CMakeLists.txt
+++ b/source/blender/modifiers/CMakeLists.txt
@@ -78,6 +78,7 @@ set(SRC
   intern/MOD_shapekey.c
   intern/MOD_shrinkwrap.c
   intern/MOD_simpledeform.c
+  intern/MOD_simulation.cc
   intern/MOD_skin.c
   intern/MOD_smooth.c
   intern/MOD_softbody.c
diff --git a/source/blender/modifiers/MOD_modifiertypes.h b/source/blender/modifiers/MOD_modifiertypes.h
index 5dc4adf4393..ba676bbe459 100644
--- a/source/blender/modifiers/MOD_modifiertypes.h
+++ b/source/blender/modifiers/MOD_modifiertypes.h
@@ -86,6 +86,7 @@ extern ModifierTypeInfo modifierType_CorrectiveSmooth;
 extern ModifierTypeInfo modifierType_MeshSequenceCache;
 extern ModifierTypeInfo modifierType_SurfaceDeform;
 extern ModifierTypeInfo modifierType_WeightedNormal;
+extern ModifierTypeInfo modifierType_Simulation;
 
 /* MOD_util.c */
 void modifier_type_init(ModifierTypeInfo *types[]);
diff --git a/source/blender/modifiers/intern/MOD_simulation.cc b/source/blender/modifiers/intern/MOD_simulation.cc
new file mode 100644
index 00000000000..f52daf53186
--- /dev/null
+++ b/source/blender/modifiers/intern/MOD_simulation.cc
@@ -0,0 +1,109 @@
+/*
+ * 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.
+ *
+ * The Original Code is Copyright (C) 2005 by the Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup modifiers
+ */
+
+#include <iostream>
+#include <string>
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_utildefines.h"
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+#include "DNA_modifier_types.h"
+#include "DNA_object_types.h"
+#include "DNA_pointcloud_types.h"
+#include "DNA_scene_types.h"
+#include "DNA_simulation_types.h"
+
+#include "BKE_customdata.h"
+#include "BKE_lib_query.h"
+#include "BKE_mesh.h"
+#include "BKE_modifier.h"
+
+#include "DEG_depsgraph_build.h"
+#include "DEG_depsgraph_query.h"
+
+#include "MOD_modifiertypes.h"
+
+static void updateDepsgraph(ModifierData *md, const ModifierUpdateDepsgraphContext *ctx)
+{
+  SimulationModifierData *smd = (SimulationModifierData *)md;
+  if (smd->simulation) {
+    DEG_add_simulation_relation(ctx->node, smd->simulation, "Accessed Simulation");
+  }
+}
+
+static void foreachIDLink(ModifierData *md, Object *ob, IDWalkFunc walk, void *userData)
+{
+  SimulationModifierData *smd = (SimulationModifierData *)md;
+  walk(userData, ob, (ID **)&smd->simulation, IDWALK_CB_USER);
+}
+
+static bool isDisabled(const struct Scene *UNUSED(scene),
+                       ModifierData *md,
+                       bool UNUSED(useRenderParams))
+{
+  SimulationModifierData *smd = (SimulationModifierData *)md;
+  return smd->simulation == nullptr;
+}
+
+static PointCloud *modifyPointCloud(ModifierData *md,
+                                    const ModifierEvalContext *UNUSED(ctx),
+                                    PointCloud *pointcloud)
+{
+  SimulationModifierData *smd = (SimulationModifierData *)md;
+  UNUSED_VARS(smd);
+  return pointcloud;
+}
+
+ModifierTypeInfo modifierType_Simulation = {
+    /* name */ "Simulation",
+    /* structName */ "SimulationModifierData",
+    /* structSize */ sizeof(SimulationModifierData),
+    /* type */ eModifierTypeType_None,
+    /* flags */ (ModifierTypeFlag)0,
+
+    /* copyData */ BKE_modifier_copydata_generic,
+
+    /* deformVerts */ NULL,
+    /* deformMatrices */ NULL,
+    /* deformVertsEM */ NULL,
+    /* deformMatricesEM */ NULL,
+    /* modifyMesh */ NULL,
+    /* modifyHair */ NULL,
+    /* modifyPointCloud */ modifyPointCloud,
+    /* modifyVolume */ NULL,
+
+    /* initData */ NULL,
+    /* requiredDataMask */ NULL,
+    /* freeData */ NULL,
+    /* isDisabled */ isDisabled,
+    /* updateDepsgraph */ updateDepsgraph,
+    /* dependsOnTime */ NULL,
+    /* dependsOnNormals */ NULL,
+    /* foreachObjectLink */ NULL,
+    /* foreachIDLink */ foreachIDLink,
+    /* foreachTexLink */ NULL,
+    /* freeRuntimeData */ NULL,
+};
diff --git a/source/blender/modifiers/intern/MOD_util.c b/source/blender/modifiers/intern/MOD_util.c
index f6b7c829c13..bd453c24a31 100644
--- a/source/blender/modifiers/intern/MOD_util.c
+++ b/source/blender/modifiers/intern/MOD_util.c
@@ -337,5 +337,6 @@ void modifier_type_init(ModifierTypeInfo *types[])
   INIT_TYPE(MeshSequenceCache);
   INIT_TYPE(SurfaceDeform);
   INIT_TYPE(WeightedNormal);
+  INIT_TYPE(Simulation);
 #undef INIT_TYPE
 }