node_geo_distribute_points_in_volume.cc

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/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#ifdef WITH_OPENVDB
#  include <openvdb/openvdb.h>
#  include <openvdb/tools/Interpolation.h>
#  include <openvdb/tools/PointScatter.h>
 
#  include <algorithm>
#endif
 
#include "DNA_node_types.h"
#include "DNA_pointcloud_types.h"
 
#include "BKE_pointcloud.hh"
#include "BKE_volume.hh"
#include "BKE_volume_grid.hh"
 
#include "GEO_foreach_geometry.hh"
#include "GEO_randomize.hh"
 
#include "node_geometry_util.hh"
 
namespace blender::nodes::node_geo_distribute_points_in_volume_cc {
 
NODE_STORAGE_FUNCS(NodeGeometryDistributePointsInVolume)
 
static const EnumPropertyItem mode_items[] = {
    {GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_RANDOM,
     "DENSITY_RANDOM",
     0,
     N_("Random"),
     N_("Distribute points randomly inside of the volume")},
    {GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_GRID,
     "DENSITY_GRID",
     0,
     N_("Grid"),
     N_("Distribute the points in a grid pattern inside of the volume")},
    {0, nullptr, 0, nullptr, nullptr},
};
 
static void node_declare(NodeDeclarationBuilder &b)
{
  b.add_input<decl::Geometry>("Volume")
      .supported_type(GeometryComponent::Type::Volume)
      .translation_context(BLT_I18NCONTEXT_ID_ID)
      .description("Volume with fog grids that points are scattered in");
  b.add_input<decl::Menu>("Mode")
      .static_items(mode_items)
      .optional_label()
      .description("Method to use for scattering points");
  b.add_input<decl::Float>("Density")
      .default_value(1.0f)
      .min(0.0f)
      .max(100000.0f)
      .subtype(PROP_NONE)
      .description("Number of points to sample per unit volume")
      .usage_by_single_menu(GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_RANDOM);
  b.add_input<decl::Int>("Seed")
      .min(-10000)
      .max(10000)
      .description("Seed used by the random number generator to generate random points")
      .usage_by_single_menu(GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_RANDOM);
  b.add_input<decl::Vector>("Spacing")
      .default_value({0.3, 0.3, 0.3})
      .min(0.0001f)
      .subtype(PROP_XYZ)
      .description("Spacing between grid points")
      .usage_by_single_menu(GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_GRID);
  b.add_input<decl::Float>("Threshold")
      .default_value(0.1f)
      .min(0.0f)
      .max(FLT_MAX)
      .description("Minimum density of a volume cell to contain a grid point")
      .usage_by_single_menu(GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_GRID);
  b.add_output<decl::Geometry>("Points").propagate_all();
}
 
static void node_init(bNodeTree * /*tree*/, bNode *node)
{
  /* Still used for forward compatibility. */
  node->storage = MEM_callocN<NodeGeometryDistributePointsInVolume>(__func__);
}
 
#ifdef WITH_OPENVDB
/* Implements the interface required by #openvdb::tools::NonUniformPointScatter. */
class PositionsVDBWrapper {
 private:
  Vector<float3> &vector_;
 
 public:
  PositionsVDBWrapper(Vector<float3> &vector) : vector_(vector) {}
  PositionsVDBWrapper(const PositionsVDBWrapper &wrapper) = default;
 
  void add(const openvdb::Vec3R &pos)
  {
    vector_.append(float3(float(pos[0]), float(pos[1]), float(pos[2])));
  }
};
 
/* Use #std::mt19937 as a random number generator,
 * it has a very long period and thus there should be no visible patterns in the generated points.
 */
using RNGType = std::mt19937;
/* Non-uniform scatter allows the amount of points to be scaled with the volume's density. */
using NonUniformPointScatterVDB =
    openvdb::tools::NonUniformPointScatter<PositionsVDBWrapper, RNGType>;
 
static void point_scatter_density_random(const openvdb::FloatGrid &grid,
                                         const float density,
                                         const int seed,
                                         Vector<float3> &r_positions)
{
  /* Setup and call into OpenVDB's point scatter API. */
  PositionsVDBWrapper vdb_position_wrapper = PositionsVDBWrapper(r_positions);
  RNGType random_generator(seed);
  NonUniformPointScatterVDB point_scatter(vdb_position_wrapper, density, random_generator);
  point_scatter(grid);
}
 
static void point_scatter_density_grid(const openvdb::FloatGrid &grid,
                                       const float3 spacing,
                                       const float threshold,
                                       Vector<float3> &r_positions)
{
  const openvdb::Vec3d half_voxel(0.5, 0.5, 0.5);
  const openvdb::Vec3d voxel_spacing(double(spacing.x) / grid.voxelSize().x(),
                                     double(spacing.y) / grid.voxelSize().y(),
                                     double(spacing.z) / grid.voxelSize().z());
 
  /* Abort if spacing is zero. */
  const double min_spacing = std::min({voxel_spacing.x(), voxel_spacing.y(), voxel_spacing.z()});
  if (std::abs(min_spacing) < 0.0001) {
    return;
  }
 
  /* Iterate through tiles and voxels on the grid. */
  for (openvdb::FloatGrid::ValueOnCIter cell = grid.cbeginValueOn(); cell; ++cell) {
    /* Check if the cell's value meets the minimum threshold. */
    if (cell.getValue() < threshold) {
      continue;
    }
    /* Compute the bounding box of each tile/voxel. */
    const openvdb::CoordBBox bbox = cell.getBoundingBox();
    const openvdb::Vec3d box_min = bbox.min().asVec3d() - half_voxel;
    const openvdb::Vec3d box_max = bbox.max().asVec3d() + half_voxel;
 
    /* Pick a starting point rounded up to the nearest possible point. */
    double abs_spacing_x = std::abs(voxel_spacing.x());
    double abs_spacing_y = std::abs(voxel_spacing.y());
    double abs_spacing_z = std::abs(voxel_spacing.z());
    const openvdb::Vec3d start(ceil(box_min.x() / abs_spacing_x) * abs_spacing_x,
                               ceil(box_min.y() / abs_spacing_y) * abs_spacing_y,
                               ceil(box_min.z() / abs_spacing_z) * abs_spacing_z);
 
    /* Iterate through all possible points in box. */
    for (double x = start.x(); x < box_max.x(); x += abs_spacing_x) {
      for (double y = start.y(); y < box_max.y(); y += abs_spacing_y) {
        for (double z = start.z(); z < box_max.z(); z += abs_spacing_z) {
          /* Transform with grid matrix and add point. */
          const openvdb::Vec3d idx_pos(x, y, z);
          const openvdb::Vec3d local_pos = grid.indexToWorld(idx_pos);
          r_positions.append({float(local_pos.x()), float(local_pos.y()), float(local_pos.z())});
        }
      }
    }
  }
}
 
#endif /* WITH_OPENVDB */
 
static void node_geo_exec(GeoNodeExecParams params)
{
#ifdef WITH_OPENVDB
  GeometrySet geometry_set = params.extract_input<GeometrySet>("Volume");
  const auto mode = params.extract_input<GeometryNodeDistributePointsInVolumeMode>("Mode");
 
  float density;
  int seed;
  float3 spacing{0, 0, 0};
  float threshold;
  if (mode == GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_RANDOM) {
    density = params.extract_input<float>("Density");
    seed = params.extract_input<int>("Seed");
  }
  else if (mode == GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_GRID) {
    spacing = params.extract_input<float3>("Spacing");
    threshold = params.extract_input<float>("Threshold");
  }
 
  geometry::foreach_real_geometry(geometry_set, [&](GeometrySet &geometry_set) {
    if (!geometry_set.has_volume()) {
      geometry_set.keep_only({GeometryComponent::Type::Edit});
      return;
    }
    const VolumeComponent *component = geometry_set.get_component<VolumeComponent>();
    const Volume *volume = component->get();
    BKE_volume_load(volume, params.bmain());
 
    Vector<float3> positions;
 
    for (const int i : IndexRange(BKE_volume_num_grids(volume))) {
      const bke::VolumeGridData *volume_grid = BKE_volume_grid_get(volume, i);
      if (volume_grid == nullptr) {
        continue;
      }
 
      bke::VolumeTreeAccessToken tree_token;
      const openvdb::GridBase &base_grid = volume_grid->grid(tree_token);
 
      if (!base_grid.isType<openvdb::FloatGrid>()) {
        continue;
      }
 
      const openvdb::FloatGrid &grid = static_cast<const openvdb::FloatGrid &>(base_grid);
 
      if (mode == GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_RANDOM) {
        point_scatter_density_random(grid, density, seed, positions);
      }
      else if (mode == GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME_DENSITY_GRID) {
        point_scatter_density_grid(grid, spacing, threshold, positions);
      }
    }
 
    PointCloud *pointcloud = BKE_pointcloud_new_nomain(positions.size());
    bke::MutableAttributeAccessor point_attributes = pointcloud->attributes_for_write();
    pointcloud->positions_for_write().copy_from(positions);
    bke::SpanAttributeWriter<float> point_radii =
        point_attributes.lookup_or_add_for_write_only_span<float>("radius", AttrDomain::Point);
 
    point_radii.span.fill(0.05f);
    point_radii.finish();
 
    geometry::debug_randomize_point_order(pointcloud);
 
    geometry_set.replace_pointcloud(pointcloud);
    geometry_set.keep_only({GeometryComponent::Type::PointCloud, GeometryComponent::Type::Edit});
  });
 
  params.set_output("Points", std::move(geometry_set));
 
#else
  node_geo_exec_with_missing_openvdb(params);
#endif
}
 
static void node_register()
{
  static blender::bke::bNodeType ntype;
  geo_node_type_base(
      &ntype, "GeometryNodeDistributePointsInVolume", GEO_NODE_DISTRIBUTE_POINTS_IN_VOLUME);
  ntype.ui_name = "Distribute Points in Volume";
  ntype.ui_description = "Generate points inside a volume";
  ntype.enum_name_legacy = "DISTRIBUTE_POINTS_IN_VOLUME";
  ntype.nclass = NODE_CLASS_GEOMETRY;
  blender::bke::node_type_storage(ntype,
                                  "NodeGeometryDistributePointsInVolume",
                                  node_free_standard_storage,
                                  node_copy_standard_storage);
  ntype.initfunc = node_init;
  blender::bke::node_type_size(ntype, 170, 100, 320);
  ntype.declare = node_declare;
  ntype.geometry_node_execute = node_geo_exec;
  blender::bke::node_register_type(ntype);
}
NOD_REGISTER_NODE(node_register)
 
}  // namespace blender::nodes::node_geo_distribute_points_in_volume_cc