Geometry Nodes: Align Euler to Vector Node

This commit introduces the Align Euler to Vector function node which
rotates to a body into a given direction. The node replaces the legacy
"Align Rotation to Vector" node, which only worked on an attribute
named `rotation` internally. The "Euler" in the name is meant to make
it clearer that the rotation isn't interchangeable with a regular
vector.

Addresses T91374.

Differential Revision: https://developer.blender.org/D12726

9 files changed, 294 insertions, 0 deletions

diff --git a/release/scripts/startup/nodeitems_builtins.py b/release/scripts/startup/nodeitems_builtins.py
index 923ea22e1e3..155fa59c315 100644
--- a/release/scripts/startup/nodeitems_builtins.py
+++ b/release/scripts/startup/nodeitems_builtins.py
@@ -630,6 +630,7 @@ geometry_node_categories = [
         NodeItem("FunctionNodeFloatToInt"),
         NodeItem("GeometryNodeSwitch"),
         NodeItem("FunctionNodeRandomValue"),
+        NodeItem("FunctionNodeAlignEulerToVector"),
     ]),
     GeometryNodeCategory("GEO_TEXTURE", "Texture", items=[
         NodeItem("ShaderNodeTexNoise"),
diff --git a/source/blender/blenkernel/BKE_node.h b/source/blender/blenkernel/BKE_node.h
index 79ae9d71762..447e0268701 100644
--- a/source/blender/blenkernel/BKE_node.h
+++ b/source/blender/blenkernel/BKE_node.h
@@ -1533,6 +1533,7 @@ int ntreeTexExecTree(struct bNodeTree *ntree,
 #define FN_NODE_INPUT_SPECIAL_CHARACTERS 1213
 #define FN_NODE_RANDOM_VALUE 1214
 #define FN_NODE_ROTATE_EULER 1215
+#define FN_NODE_ALIGN_EULER_TO_VECTOR 1216
 
 /** \} */
 
diff --git a/source/blender/blenkernel/intern/node.cc b/source/blender/blenkernel/intern/node.cc
index 75b9d07ca98..cad5d4eff41 100644
--- a/source/blender/blenkernel/intern/node.cc
+++ b/source/blender/blenkernel/intern/node.cc
@@ -5818,6 +5818,7 @@ static void registerFunctionNodes()
 {
   register_node_type_fn_legacy_random_float();
 
+  register_node_type_fn_align_euler_to_vector();
   register_node_type_fn_boolean_math();
   register_node_type_fn_float_compare();
   register_node_type_fn_float_to_int();
diff --git a/source/blender/makesdna/DNA_node_types.h b/source/blender/makesdna/DNA_node_types.h
index edbb0070462..cbfa4e702ea 100644
--- a/source/blender/makesdna/DNA_node_types.h
+++ b/source/blender/makesdna/DNA_node_types.h
@@ -2075,6 +2075,19 @@ typedef enum GeometryNodeAlignRotationToVectorPivotAxis {
   GEO_NODE_ALIGN_ROTATION_TO_VECTOR_PIVOT_AXIS_Z = 3,
 } GeometryNodeAlignRotationToVectorPivotAxis;
 
+typedef enum NodeAlignEulerToVectorAxis {
+  FN_NODE_ALIGN_EULER_TO_VECTOR_AXIS_X = 0,
+  FN_NODE_ALIGN_EULER_TO_VECTOR_AXIS_Y = 1,
+  FN_NODE_ALIGN_EULER_TO_VECTOR_AXIS_Z = 2,
+} NodeAlignEulerToVectorAxis;
+
+typedef enum NodeAlignEulerToVectorPivotAxis {
+  FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_AUTO = 0,
+  FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_X = 1,
+  FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_Y = 2,
+  FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_Z = 3,
+} NodeAlignEulerToVectorPivotAxis;
+
 typedef enum GeometryNodeTransformSpace {
   GEO_NODE_TRANSFORM_SPACE_ORIGINAL = 0,
   GEO_NODE_TRANSFORM_SPACE_RELATIVE = 1,
diff --git a/source/blender/makesrna/intern/rna_nodetree.c b/source/blender/makesrna/intern/rna_nodetree.c
index 5e997f81753..cab420ba990 100644
--- a/source/blender/makesrna/intern/rna_nodetree.c
+++ b/source/blender/makesrna/intern/rna_nodetree.c
@@ -9952,6 +9952,66 @@ static void def_geo_align_rotation_to_vector(StructRNA *srna)
   RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_socket_update");
 }
 
+static void def_fn_align_euler_to_vector(StructRNA *srna)
+{
+  static const EnumPropertyItem axis_items[] = {
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_AXIS_X,
+       "X",
+       ICON_NONE,
+       "X",
+       "Align the X axis with the vector"},
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_AXIS_Y,
+       "Y",
+       ICON_NONE,
+       "Y",
+       "Align the Y axis with the vector"},
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_AXIS_Z,
+       "Z",
+       ICON_NONE,
+       "Z",
+       "Align the Z axis with the vector"},
+      {0, NULL, 0, NULL, NULL},
+  };
+
+  static const EnumPropertyItem pivot_axis_items[] = {
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_AUTO,
+       "AUTO",
+       ICON_NONE,
+       "Auto",
+       "Automatically detect the best rotation axis to rotate towards the vector"},
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_X,
+       "X",
+       ICON_NONE,
+       "X",
+       "Rotate around the local X axis"},
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_Y,
+       "Y",
+       ICON_NONE,
+       "Y",
+       "Rotate around the local Y axis"},
+      {FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_Z,
+       "Z",
+       ICON_NONE,
+       "Z",
+       "Rotate around the local Z axis"},
+      {0, NULL, 0, NULL, NULL},
+  };
+
+  PropertyRNA *prop;
+
+  prop = RNA_def_property(srna, "axis", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_sdna(prop, NULL, "custom1");
+  RNA_def_property_enum_items(prop, axis_items);
+  RNA_def_property_ui_text(prop, "Axis", "Axis to align to the vector");
+  RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+
+  prop = RNA_def_property(srna, "pivot_axis", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_sdna(prop, NULL, "custom2");
+  RNA_def_property_enum_items(prop, pivot_axis_items);
+  RNA_def_property_ui_text(prop, "Pivot Axis", "Axis to rotate around");
+  RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+}
+
 static void def_geo_point_scale(StructRNA *srna)
 {
   PropertyRNA *prop;
diff --git a/source/blender/nodes/CMakeLists.txt b/source/blender/nodes/CMakeLists.txt
index a4350c10087..78a9bb72e26 100644
--- a/source/blender/nodes/CMakeLists.txt
+++ b/source/blender/nodes/CMakeLists.txt
@@ -135,6 +135,7 @@ set(SRC
 
   function/nodes/legacy/node_fn_random_float.cc
 
+  function/nodes/node_fn_align_euler_to_vector.cc
   function/nodes/node_fn_boolean_math.cc
   function/nodes/node_fn_float_compare.cc
   function/nodes/node_fn_float_to_int.cc
diff --git a/source/blender/nodes/NOD_function.h b/source/blender/nodes/NOD_function.h
index 450e999bea4..395a2d68b53 100644
--- a/source/blender/nodes/NOD_function.h
+++ b/source/blender/nodes/NOD_function.h
@@ -22,6 +22,7 @@ extern "C" {
 
 void register_node_type_fn_legacy_random_float(void);
 
+void register_node_type_fn_align_euler_to_vector(void);
 void register_node_type_fn_boolean_math(void);
 void register_node_type_fn_float_compare(void);
 void register_node_type_fn_float_to_int(void);
diff --git a/source/blender/nodes/NOD_static_types.h b/source/blender/nodes/NOD_static_types.h
index 7e10b4055fd..80468adf3bc 100644
--- a/source/blender/nodes/NOD_static_types.h
+++ b/source/blender/nodes/NOD_static_types.h
@@ -265,6 +265,7 @@ DefNode(TextureNode,    TEX_NODE_PROC+TEX_DISTNOISE, 0,                  "TEX_DI
 
 DefNode(FunctionNode, FN_NODE_LEGACY_RANDOM_FLOAT, 0, "LEGACY_RANDOM_FLOAT", LegacyRandomFloat, "Random Float", "")
 
+DefNode(FunctionNode, FN_NODE_ALIGN_EULER_TO_VECTOR, def_fn_align_euler_to_vector, "ALIGN_EULER_TO_VECTOR", AlignEulerToVector, "Align Euler To Vector", "")
 DefNode(FunctionNode, FN_NODE_BOOLEAN_MATH,  def_boolean_math,  "BOOLEAN_MATH",  BooleanMath,  "Boolean Math", "")
 DefNode(FunctionNode, FN_NODE_FLOAT_COMPARE, def_float_compare, "FLOAT_COMPARE", FloatCompare, "Float Compare", "")
 DefNode(FunctionNode, FN_NODE_FLOAT_TO_INT, def_float_to_int, "FLOAT_TO_INT", FloatToInt, "Float to Integer", "")
diff --git a/source/blender/nodes/function/nodes/node_fn_align_euler_to_vector.cc b/source/blender/nodes/function/nodes/node_fn_align_euler_to_vector.cc
new file mode 100644
index 00000000000..4c741c96bb8
--- /dev/null
+++ b/source/blender/nodes/function/nodes/node_fn_align_euler_to_vector.cc
@@ -0,0 +1,215 @@
+/*
+ * 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 "BLI_task.hh"
+
+#include "RNA_enum_types.h"
+
+#include "UI_interface.h"
+#include "UI_resources.h"
+
+#include "node_function_util.hh"
+
+namespace blender::nodes {
+
+static void fn_node_align_euler_to_vector_declare(NodeDeclarationBuilder &b)
+{
+  b.is_function_node();
+  b.add_input<decl::Vector>("Rotation").subtype(PROP_EULER).hide_value();
+  b.add_input<decl::Float>("Factor").default_value(1.0f).min(0.0f).max(1.0f).subtype(PROP_FACTOR);
+  b.add_input<decl::Vector>("Vector").default_value({0.0, 0.0, 1.0});
+  b.add_output<decl::Vector>("Rotation").subtype(PROP_EULER);
+}
+
+static void fn_node_align_euler_to_vector_layout(uiLayout *layout,
+                                                 bContext *UNUSED(C),
+                                                 PointerRNA *ptr)
+{
+  uiItemR(layout, ptr, "axis", UI_ITEM_R_EXPAND, nullptr, ICON_NONE);
+  uiLayoutSetPropSep(layout, true);
+  uiLayoutSetPropDecorate(layout, false);
+  uiItemR(layout, ptr, "pivot_axis", 0, IFACE_("Pivot"), ICON_NONE);
+}
+
+static void align_rotations_auto_pivot(IndexMask mask,
+                                       const VArray<float3> &input_rotations,
+                                       const VArray<float3> &vectors,
+                                       const VArray<float> &factors,
+                                       const float3 local_main_axis,
+                                       const MutableSpan<float3> output_rotations)
+{
+  threading::parallel_for(mask.index_range(), 512, [&](IndexRange mask_range) {
+    for (const int maski : mask_range) {
+      const int64_t i = mask[maski];
+      const float3 vector = vectors[i];
+      if (is_zero_v3(vector)) {
+        output_rotations[i] = input_rotations[i];
+      }
+
+      float old_rotation[3][3];
+      eul_to_mat3(old_rotation, input_rotations[i]);
+      float3 old_axis;
+      mul_v3_m3v3(old_axis, old_rotation, local_main_axis);
+
+      const float3 new_axis = vector.normalized();
+      float3 rotation_axis = float3::cross_high_precision(old_axis, new_axis);
+      if (is_zero_v3(rotation_axis)) {
+        /* The vectors are linearly dependent, so we fall back to another axis. */
+        rotation_axis = float3::cross_high_precision(old_axis, float3(1, 0, 0));
+        if (is_zero_v3(rotation_axis)) {
+          /* This is now guaranteed to not be zero. */
+          rotation_axis = float3::cross_high_precision(old_axis, float3(0, 1, 0));
+        }
+      }
+
+      const float full_angle = angle_normalized_v3v3(old_axis, new_axis);
+      const float angle = factors[i] * full_angle;
+
+      float rotation[3][3];
+      axis_angle_to_mat3(rotation, rotation_axis, angle);
+
+      float new_rotation_matrix[3][3];
+      mul_m3_m3m3(new_rotation_matrix, rotation, old_rotation);
+
+      float3 new_rotation;
+      mat3_to_eul(new_rotation, new_rotation_matrix);
+
+      output_rotations[i] = new_rotation;
+    }
+  });
+}
+
+static void align_rotations_fixed_pivot(IndexMask mask,
+                                        const VArray<float3> &input_rotations,
+                                        const VArray<float3> &vectors,
+                                        const VArray<float> &factors,
+                                        const float3 local_main_axis,
+                                        const float3 local_pivot_axis,
+                                        const MutableSpan<float3> output_rotations)
+{
+  threading::parallel_for(mask.index_range(), 512, [&](IndexRange mask_range) {
+    for (const int64_t maski : mask_range) {
+      const int64_t i = mask[maski];
+      if (local_main_axis == local_pivot_axis) {
+        /* Can't compute any meaningful rotation angle in this case. */
+        output_rotations[i] = input_rotations[i];
+      }
+
+      const float3 vector = vectors[i];
+      if (is_zero_v3(vector)) {
+        continue;
+      }
+
+      float old_rotation[3][3];
+      eul_to_mat3(old_rotation, input_rotations[i]);
+      float3 old_axis;
+      mul_v3_m3v3(old_axis, old_rotation, local_main_axis);
+      float3 pivot_axis;
+      mul_v3_m3v3(pivot_axis, old_rotation, local_pivot_axis);
+
+      float full_angle = angle_signed_on_axis_v3v3_v3(vector, old_axis, pivot_axis);
+      if (full_angle > M_PI) {
+        /* Make sure the point is rotated as little as possible. */
+        full_angle -= 2.0f * M_PI;
+      }
+      const float angle = factors[i] * full_angle;
+
+      float rotation[3][3];
+      axis_angle_to_mat3(rotation, pivot_axis, angle);
+
+      float new_rotation_matrix[3][3];
+      mul_m3_m3m3(new_rotation_matrix, rotation, old_rotation);
+
+      float3 new_rotation;
+      mat3_to_eul(new_rotation, new_rotation_matrix);
+
+      output_rotations[i] = new_rotation;
+    }
+  });
+}
+
+class MF_AlignEulerToVector : public fn::MultiFunction {
+ private:
+  int main_axis_mode_;
+  int pivot_axis_mode_;
+
+ public:
+  MF_AlignEulerToVector(int main_axis_mode, int pivot_axis_mode)
+      : main_axis_mode_(main_axis_mode), pivot_axis_mode_(pivot_axis_mode)
+  {
+    static fn::MFSignature signature = create_signature();
+    this->set_signature(&signature);
+  }
+
+  static fn::MFSignature create_signature()
+  {
+    fn::MFSignatureBuilder signature{"Align Euler To Vector"};
+    signature.single_input<float3>("Rotation");
+    signature.single_input<float>("Factor");
+    signature.single_input<float3>("Vector");
+
+    signature.single_output<float3>("Rotation");
+    return signature.build();
+  }
+
+  void call(IndexMask mask, fn::MFParams params, fn::MFContext UNUSED(context)) const override
+  {
+    const VArray<float3> &input_rotations = params.readonly_single_input<float3>(0, "Rotation");
+    const VArray<float> &factors = params.readonly_single_input<float>(1, "Factor");
+    const VArray<float3> &vectors = params.readonly_single_input<float3>(2, "Vector");
+
+    auto output_rotations = params.uninitialized_single_output<float3>(3, "Rotation");
+
+    float3 local_main_axis = {0.0f, 0.0f, 0.0f};
+    local_main_axis[main_axis_mode_] = 1;
+
+    if (pivot_axis_mode_ == FN_NODE_ALIGN_EULER_TO_VECTOR_PIVOT_AXIS_AUTO) {
+      align_rotations_auto_pivot(
+          mask, input_rotations, vectors, factors, local_main_axis, output_rotations);
+    }
+    else {
+      float3 local_pivot_axis = {0.0f, 0.0f, 0.0f};
+      local_pivot_axis[main_axis_mode_] = 1;
+      align_rotations_fixed_pivot(mask,
+                                  input_rotations,
+                                  vectors,
+                                  factors,
+                                  local_main_axis,
+                                  local_pivot_axis,
+                                  output_rotations);
+    }
+  }
+};
+
+static void fn_node_align_euler_to_vector_build_multi_function(NodeMultiFunctionBuilder &builder)
+{
+  bNode &node = builder.node();
+  builder.construct_and_set_matching_fn<MF_AlignEulerToVector>(node.custom1, node.custom2);
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_fn_align_euler_to_vector()
+{
+  static bNodeType ntype;
+
+  fn_node_type_base(
+      &ntype, FN_NODE_ALIGN_EULER_TO_VECTOR, "Align Euler to Vector", NODE_CLASS_CONVERTER, 0);
+  ntype.declare = blender::nodes::fn_node_align_euler_to_vector_declare;
+  ntype.draw_buttons = blender::nodes::fn_node_align_euler_to_vector_layout;
+  ntype.build_multi_function = blender::nodes::fn_node_align_euler_to_vector_build_multi_function;
+  nodeRegisterType(&ntype);
+}