Geometry Nodes: initial scattering and geometry nodes

This is the initial merge from the geometry-nodes branch.
Nodes:
* Attribute Math
* Boolean
* Edge Split
* Float Compare
* Object Info
* Point Distribute
* Point Instance
* Random Attribute
* Random Float
* Subdivision Surface
* Transform
* Triangulate

It includes the initial evaluation of geometry node groups in the Geometry Nodes modifier.

Notes on the Generic attribute access API

The API adds an indirection for attribute access. That has the following benefits:
* Most code does not have to care about how an attribute is stored internally.
  This is mainly necessary, because we have to deal with "legacy" attributes
  such as vertex weights and attributes that are embedded into other structs
  such as vertex positions.
* When reading from an attribute, we generally don't care what domain the
  attribute is stored on. So we want to abstract away the interpolation that
  that adapts attributes from one domain to another domain (this is not
  actually implemented yet).

Other possible improvements for later iterations include:
* Actually implement interpolation between domains.
* Don't use inheritance for the different attribute types. A single class for read
  access and one for write access might be enough, because we know all the ways
  in which attributes are stored internally. We don't want more different internal
  structures in the future. On the contrary, ideally we can consolidate the different
  storage formats in the future to reduce the need for this indirection.
* Remove the need for heap allocations when creating attribute accessors.

It includes commits from:
* Dalai Felinto
* Hans Goudey
* Jacques Lucke
* Léo Depoix

5 files changed, 191 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_rand.h b/source/blender/blenlib/BLI_rand.h
index 78a323c2431..ec74cef9311 100644
--- a/source/blender/blenlib/BLI_rand.h
+++ b/source/blender/blenlib/BLI_rand.h
@@ -60,6 +60,12 @@ void BLI_rng_get_tri_sample_float_v2(struct RNG *rng,
                                      const float v2[2],
                                      const float v3[2],
                                      float r_pt[2]) ATTR_NONNULL();
+void BLI_rng_get_tri_sample_float_v3(RNG *rng,
+                                     const float v1[3],
+                                     const float v2[3],
+                                     const float v3[3],
+                                     float r_pt[3]) ATTR_NONNULL();
+
 void BLI_rng_shuffle_array(struct RNG *rng,
                            void *data,
                            unsigned int elem_size_i,
diff --git a/source/blender/blenlib/BLI_rand.hh b/source/blender/blenlib/BLI_rand.hh
index 1b321bd7bcd..0c0dd464d4d 100644
--- a/source/blender/blenlib/BLI_rand.hh
+++ b/source/blender/blenlib/BLI_rand.hh
@@ -118,6 +118,7 @@ class RandomNumberGenerator {
   float2 get_unit_float2();
   float3 get_unit_float3();
   float2 get_triangle_sample(float2 v1, float2 v2, float2 v3);
+  float3 get_triangle_sample_3d(float3 v1, float3 v2, float3 v3);
   void get_bytes(MutableSpan<char> r_bytes);
 
   /**
diff --git a/source/blender/blenlib/BLI_user_counter.hh b/source/blender/blenlib/BLI_user_counter.hh
new file mode 100644
index 00000000000..ef276814981
--- /dev/null
+++ b/source/blender/blenlib/BLI_user_counter.hh
@@ -0,0 +1,158 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup bli
+ */
+
+#include <atomic>
+
+namespace blender {
+
+/**
+ * A simple automatic reference counter. It is similar to std::shared_ptr, but expects that the
+ * reference count is inside the object.
+ */
+template<typename T> class UserCounter {
+ private:
+  T *data_ = nullptr;
+
+ public:
+  UserCounter() = default;
+
+  UserCounter(T *data) : data_(data)
+  {
+  }
+
+  UserCounter(const UserCounter &other) : data_(other.data_)
+  {
+    this->user_add(data_);
+  }
+
+  UserCounter(UserCounter &&other) : data_(other.data_)
+  {
+    other.data_ = nullptr;
+  }
+
+  ~UserCounter()
+  {
+    this->user_remove(data_);
+  }
+
+  UserCounter &operator=(const UserCounter &other)
+  {
+    if (this == &other) {
+      return *this;
+    }
+
+    this->user_remove(data_);
+    data_ = other.data_;
+    this->user_add(data_);
+    return *this;
+  }
+
+  UserCounter &operator=(UserCounter &&other)
+  {
+    if (this == &other) {
+      return *this;
+    }
+
+    this->user_remove(data_);
+    data_ = other.data_;
+    other.data_ = nullptr;
+    return *this;
+  }
+
+  T *operator->()
+  {
+    BLI_assert(data_ != nullptr);
+    return data_;
+  }
+
+  T &operator*()
+  {
+    BLI_assert(data_ != nullptr);
+    return *data_;
+  }
+
+  operator bool() const
+  {
+    return data_ != nullptr;
+  }
+
+  T *get()
+  {
+    return data_;
+  }
+
+  const T *get() const
+  {
+    return data_;
+  }
+
+  T *release()
+  {
+    T *data = data_;
+    data_ = nullptr;
+    return data;
+  }
+
+  void reset()
+  {
+    this->user_remove(data_);
+    data_ = nullptr;
+  }
+
+  bool has_value() const
+  {
+    return data_ != nullptr;
+  }
+
+  uint64_t hash() const
+  {
+    return DefaultHash<T *>{}(data_);
+  }
+
+  friend bool operator==(const UserCounter &a, const UserCounter &b)
+  {
+    return a.data_ == b.data_;
+  }
+
+  friend std::ostream &operator<<(std::ostream &stream, const UserCounter &value)
+  {
+    stream << value.data_;
+    return stream;
+  }
+
+ private:
+  static void user_add(T *data)
+  {
+    if (data != nullptr) {
+      data->user_add();
+    }
+  }
+
+  static void user_remove(T *data)
+  {
+    if (data != nullptr) {
+      data->user_remove();
+    }
+  }
+};
+
+}  // namespace blender
diff --git a/source/blender/blenlib/CMakeLists.txt b/source/blender/blenlib/CMakeLists.txt
index 9736d8f9b3b..46a3ad87dfe 100644
--- a/source/blender/blenlib/CMakeLists.txt
+++ b/source/blender/blenlib/CMakeLists.txt
@@ -279,6 +279,7 @@ set(SRC
   BLI_timecode.h
   BLI_timeit.hh
   BLI_timer.h
+  BLI_user_counter.hh
   BLI_utildefines.h
   BLI_utildefines_iter.h
   BLI_utildefines_stack.h
diff --git a/source/blender/blenlib/intern/rand.cc b/source/blender/blenlib/intern/rand.cc
index 224db31471d..c61e17e6627 100644
--- a/source/blender/blenlib/intern/rand.cc
+++ b/source/blender/blenlib/intern/rand.cc
@@ -141,6 +141,12 @@ void BLI_rng_get_tri_sample_float_v2(
   copy_v2_v2(r_pt, rng->rng.get_triangle_sample(v1, v2, v3));
 }
 
+void BLI_rng_get_tri_sample_float_v3(
+    RNG *rng, const float v1[3], const float v2[3], const float v3[3], float r_pt[3])
+{
+  copy_v3_v3(r_pt, rng->rng.get_triangle_sample_3d(v1, v2, v3));
+}
+
 void BLI_rng_shuffle_array(RNG *rng, void *data, unsigned int elem_size_i, unsigned int elem_tot)
 {
   const uint elem_size = elem_size_i;
@@ -425,6 +431,25 @@ float2 RandomNumberGenerator::get_triangle_sample(float2 v1, float2 v2, float2 v
   return sample;
 }
 
+float3 RandomNumberGenerator::get_triangle_sample_3d(float3 v1, float3 v2, float3 v3)
+{
+  float u = this->get_float();
+  float v = this->get_float();
+
+  if (u + v > 1.0f) {
+    u = 1.0f - u;
+    v = 1.0f - v;
+  }
+
+  float3 side_u = v2 - v1;
+  float3 side_v = v3 - v1;
+
+  float3 sample = v1;
+  sample += side_u * u;
+  sample += side_v * v;
+  return sample;
+}
+
 void RandomNumberGenerator::get_bytes(MutableSpan<char> r_bytes)
 {
   constexpr int64_t mask_bytes = 2;