Geometry Nodes: add Volume to Mesh node

This node takes a volume and generates a mesh on it's "surface".
The surface is defined by a threshold value.

Currently, the node only works on volumes generated by the
Points to Volume node. This limitation will be resolved soonish.

Ref T84605.

Differential Revision: https://developer.blender.org/D10243

4 files changed, 163 insertions, 1 deletions

diff --git a/source/blender/nodes/CMakeLists.txt b/source/blender/nodes/CMakeLists.txt
index 76b19685456..a209faa5d17 100644
--- a/source/blender/nodes/CMakeLists.txt
+++ b/source/blender/nodes/CMakeLists.txt
@@ -167,6 +167,7 @@ set(SRC
   geometry/nodes/node_geo_subdivision_surface.cc
   geometry/nodes/node_geo_transform.cc
   geometry/nodes/node_geo_triangulate.cc
+  geometry/nodes/node_geo_volume_to_mesh.cc
   geometry/node_geometry_exec.cc
   geometry/node_geometry_tree.cc
   geometry/node_geometry_util.cc
diff --git a/source/blender/nodes/NOD_geometry.h b/source/blender/nodes/NOD_geometry.h
index 54a728f5bfe..d4d137c8fc5 100644
--- a/source/blender/nodes/NOD_geometry.h
+++ b/source/blender/nodes/NOD_geometry.h
@@ -52,6 +52,7 @@ void register_node_type_geo_sample_texture(void);
 void register_node_type_geo_points_to_volume(void);
 void register_node_type_geo_collection_info(void);
 void register_node_type_geo_is_viewport(void);
+void register_node_type_geo_volume_to_mesh(void);
 
 #ifdef __cplusplus
 }
diff --git a/source/blender/nodes/NOD_static_types.h b/source/blender/nodes/NOD_static_types.h
index 1cf08a419c9..980790af766 100644
--- a/source/blender/nodes/NOD_static_types.h
+++ b/source/blender/nodes/NOD_static_types.h
@@ -294,7 +294,7 @@ DefNode(GeometryNode, GEO_NODE_POINTS_TO_VOLUME, def_geo_points_to_volume, "POIN
 DefNode(GeometryNode, GEO_NODE_COLLECTION_INFO, def_geo_collection_info, "COLLECTION_INFO", CollectionInfo, "Collection Info", "")
 DefNode(GeometryNode, GEO_NODE_IS_VIEWPORT, 0, "IS_VIEWPORT", IsViewport, "Is Viewport", "")
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_PROXIMITY, def_geo_attribute_proximity, "ATTRIBUTE_PROXIMITY", AttributeProximity, "Attribute Proximity", "")
-
+DefNode(GeometryNode, GEO_NODE_VOLUME_TO_MESH, def_geo_volume_to_mesh, "VOLUME_TO_MESH", VolumeToMesh, "Volume to Mesh", "")
 
 /* undefine macros */
 #undef DefNode
diff --git a/source/blender/nodes/geometry/nodes/node_geo_volume_to_mesh.cc b/source/blender/nodes/geometry/nodes/node_geo_volume_to_mesh.cc
new file mode 100644
index 00000000000..b1d1430bccd
--- /dev/null
+++ b/source/blender/nodes/geometry/nodes/node_geo_volume_to_mesh.cc
@@ -0,0 +1,160 @@
+/*
+ * 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 "DEG_depsgraph_query.h"
+#ifdef WITH_OPENVDB
+#  include <openvdb/tools/GridTransformer.h>
+#  include <openvdb/tools/VolumeToMesh.h>
+#endif
+
+#include "node_geometry_util.hh"
+
+#include "BKE_lib_id.h"
+#include "BKE_mesh.h"
+#include "BKE_mesh_runtime.h"
+#include "BKE_volume.h"
+#include "BKE_volume_to_mesh.hh"
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+
+static bNodeSocketTemplate geo_node_volume_to_mesh_in[] = {
+    {SOCK_GEOMETRY, N_("Geometry")},
+    {SOCK_STRING, N_("Grid")},
+    {SOCK_FLOAT, N_("Voxel Size"), 0.3f, 0.0f, 0.0f, 0.0f, 0.01f, FLT_MAX},
+    {SOCK_FLOAT, N_("Voxel Amount"), 64.0f, 0.0f, 0.0f, 0.0f, 0.0f, FLT_MAX},
+    {SOCK_FLOAT, N_("Threshold"), 0.1f, 0.0f, 0.0f, 0.0f, 0.0f, FLT_MAX},
+    {SOCK_FLOAT, N_("Adaptivity"), 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, PROP_FACTOR},
+    {-1, ""},
+};
+
+static bNodeSocketTemplate geo_node_volume_to_mesh_out[] = {
+    {SOCK_GEOMETRY, N_("Geometry")},
+    {-1, ""},
+};
+
+namespace blender::nodes {
+
+static void geo_node_volume_to_mesh_init(bNodeTree *UNUSED(ntree), bNode *node)
+{
+  NodeGeometryVolumeToMesh *data = (NodeGeometryVolumeToMesh *)MEM_callocN(
+      sizeof(NodeGeometryVolumeToMesh), __func__);
+  data->resolution_mode = VOLUME_TO_MESH_RESOLUTION_MODE_GRID;
+
+  bNodeSocket *grid_socket = nodeFindSocket(node, SOCK_IN, "Grid");
+  bNodeSocketValueString *grid_socket_value = (bNodeSocketValueString *)grid_socket->default_value;
+  STRNCPY(grid_socket_value->value, "density");
+
+  node->storage = data;
+}
+
+static void geo_node_volume_to_mesh_update(bNodeTree *UNUSED(ntree), bNode *node)
+{
+  NodeGeometryVolumeToMesh *data = (NodeGeometryVolumeToMesh *)node->storage;
+
+  bNodeSocket *voxel_size_socket = nodeFindSocket(node, SOCK_IN, "Voxel Size");
+  bNodeSocket *voxel_amount_socket = nodeFindSocket(node, SOCK_IN, "Voxel Amount");
+  nodeSetSocketAvailability(voxel_amount_socket,
+                            data->resolution_mode == VOLUME_TO_MESH_RESOLUTION_MODE_VOXEL_AMOUNT);
+  nodeSetSocketAvailability(voxel_size_socket,
+                            data->resolution_mode == VOLUME_TO_MESH_RESOLUTION_MODE_VOXEL_SIZE);
+}
+
+#ifdef WITH_OPENVDB
+
+static void create_mesh_from_volume(GeometrySet &geometry_set_in,
+                                    GeometrySet &geometry_set_out,
+                                    GeoNodeExecParams &params)
+{
+  if (!geometry_set_in.has<VolumeComponent>()) {
+    return;
+  }
+
+  const NodeGeometryVolumeToMesh &storage =
+      *(const NodeGeometryVolumeToMesh *)params.node().storage;
+
+  bke::VolumeToMeshResolution resolution;
+  resolution.mode = (VolumeToMeshResolutionMode)storage.resolution_mode;
+  if (resolution.mode == VOLUME_TO_MESH_RESOLUTION_MODE_VOXEL_AMOUNT) {
+    resolution.settings.voxel_amount = params.get_input<float>("Voxel Amount");
+    if (resolution.settings.voxel_amount <= 0.0f) {
+      return;
+    }
+  }
+  else if (resolution.mode == VOLUME_TO_MESH_RESOLUTION_MODE_VOXEL_SIZE) {
+    resolution.settings.voxel_size = params.get_input<float>("Voxel Size");
+    if (resolution.settings.voxel_size <= 0.0f) {
+      return;
+    }
+  }
+
+  const VolumeComponent *component = geometry_set_in.get_component_for_read<VolumeComponent>();
+  const Volume *volume = component->get_for_read();
+  if (volume == nullptr) {
+    return;
+  }
+
+  Main *bmain = DEG_get_bmain(params.depsgraph());
+  BKE_volume_load(const_cast<Volume *>(volume), bmain);
+
+  const std::string grid_name = params.get_input<std::string>("Grid");
+  VolumeGrid *volume_grid = BKE_volume_grid_find(volume, grid_name.c_str());
+  if (volume_grid == nullptr) {
+    return;
+  }
+
+  float threshold = params.get_input<float>("Threshold");
+  float adaptivity = params.get_input<float>("Adaptivity");
+
+  const openvdb::GridBase::ConstPtr grid = BKE_volume_grid_openvdb_for_read(volume, volume_grid);
+  Mesh *mesh = bke::volume_to_mesh(*grid, resolution, threshold, adaptivity);
+  if (mesh == nullptr) {
+    return;
+  }
+  MeshComponent &dst_component = geometry_set_out.get_component_for_write<MeshComponent>();
+  dst_component.replace(mesh);
+}
+
+#endif /* WITH_OPENVDB */
+
+static void geo_node_volume_to_mesh_exec(GeoNodeExecParams params)
+{
+  GeometrySet geometry_set_in = params.extract_input<GeometrySet>("Geometry");
+  GeometrySet geometry_set_out;
+
+#ifdef WITH_OPENVDB
+  create_mesh_from_volume(geometry_set_in, geometry_set_out, params);
+#endif
+
+  params.set_output("Geometry", geometry_set_out);
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_volume_to_mesh()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_VOLUME_TO_MESH, "Volume to Mesh", NODE_CLASS_GEOMETRY, 0);
+  node_type_socket_templates(&ntype, geo_node_volume_to_mesh_in, geo_node_volume_to_mesh_out);
+  node_type_storage(
+      &ntype, "NodeGeometryVolumeToMesh", node_free_standard_storage, node_copy_standard_storage);
+  node_type_size(&ntype, 200, 120, 700);
+  node_type_init(&ntype, blender::nodes::geo_node_volume_to_mesh_init);
+  node_type_update(&ntype, blender::nodes::geo_node_volume_to_mesh_update);
+  ntype.geometry_node_execute = blender::nodes::geo_node_volume_to_mesh_exec;
+  nodeRegisterType(&ntype);
+}