Geometry Nodes: Multi-Input Sockets

Normally sockets only have one input link. This commit adds the back-end
changes needed to use multiple input links per socket.

Multi-input sockets can be defined with a new flag in `bNodeSocketType`.
The changes necessary to make the sockets work in the geometry nodes
evaluator are generalizing input socket values as a vector of values,
and supporting this in the derived node tree structure.

This patch should contain no functional changes. Two upcoming patches
will use this system for the "Join Geometry" node and expose link picking
and updated display in the UI: D10069 and D10181.

Reviewed By: Jacques Lucke, Hans Goudey

Differential Revision: https://developer.blender.org/D10067

1 files changed, 64 insertions, 23 deletions

diff --git a/source/blender/modifiers/intern/MOD_nodes.cc b/source/blender/modifiers/intern/MOD_nodes.cc
index 6ce288e8ac5..74cfcefc842 100644
--- a/source/blender/modifiers/intern/MOD_nodes.cc
+++ b/source/blender/modifiers/intern/MOD_nodes.cc
@@ -215,7 +215,7 @@ static bool isDisabled(const struct Scene *UNUSED(scene),
 class GeometryNodesEvaluator {
  private:
   blender::LinearAllocator<> allocator_;
-  Map<const DInputSocket *, GMutablePointer> value_by_input_;
+  Map<std::pair<const DInputSocket *, const DOutputSocket *>, GMutablePointer> value_by_input_;
   Vector<const DInputSocket *> group_outputs_;
   blender::nodes::MultiFunctionByNode &mf_by_node_;
   const blender::nodes::DataTypeConversions &conversions_;
@@ -246,8 +246,8 @@ class GeometryNodesEvaluator {
   {
     Vector<GMutablePointer> results;
     for (const DInputSocket *group_output : group_outputs_) {
-      GMutablePointer result = this->get_input_value(*group_output);
-      results.append(result);
+      Vector<GMutablePointer> result = this->get_input_values(*group_output);
+      results.append(result[0]);
     }
     for (GMutablePointer value : value_by_input_.values()) {
       value.destruct();
@@ -256,32 +256,53 @@ class GeometryNodesEvaluator {
   }
 
  private:
-  GMutablePointer get_input_value(const DInputSocket &socket_to_compute)
+  Vector<GMutablePointer> get_input_values(const DInputSocket &socket_to_compute)
   {
-    std::optional<GMutablePointer> value = value_by_input_.pop_try(&socket_to_compute);
-    if (value.has_value()) {
-      /* This input has been computed before, return it directly. */
-      return *value;
-    }
 
     Span<const DOutputSocket *> from_sockets = socket_to_compute.linked_sockets();
     Span<const DGroupInput *> from_group_inputs = socket_to_compute.linked_group_inputs();
     const int total_inputs = from_sockets.size() + from_group_inputs.size();
-    BLI_assert(total_inputs <= 1);
 
     if (total_inputs == 0) {
       /* The input is not connected, use the value from the socket itself. */
-      return get_unlinked_input_value(socket_to_compute);
+      return {get_unlinked_input_value(socket_to_compute)};
     }
+
     if (from_group_inputs.size() == 1) {
-      /* The input gets its value from the input of a group that is not further connected. */
-      return get_unlinked_input_value(socket_to_compute);
+      return {get_unlinked_input_value(socket_to_compute)};
+    }
+
+    /* Multi-input sockets contain a vector of inputs. */
+    if (socket_to_compute.is_multi_input_socket()) {
+      Vector<GMutablePointer> values;
+      for (const DOutputSocket *from_socket : from_sockets) {
+        const std::pair<const DInputSocket *, const DOutputSocket *> key = std::make_pair(
+            &socket_to_compute, from_socket);
+        std::optional<GMutablePointer> value = value_by_input_.pop_try(key);
+        if (value.has_value()) {
+          values.append(value.value());
+        }
+        else {
+          this->compute_output_and_forward(*from_socket);
+          GMutablePointer value = value_by_input_.pop(key);
+          values.append(value);
+        }
+      }
+      return values;
     }
 
-    /* Compute the socket now. */
     const DOutputSocket &from_socket = *from_sockets[0];
+    const std::pair<const DInputSocket *, const DOutputSocket *> key = std::make_pair(
+        &socket_to_compute, &from_socket);
+    std::optional<GMutablePointer> value = value_by_input_.pop_try(key);
+    if (value.has_value()) {
+      /* This input has been computed before, return it directly. */
+      return {*value};
+    }
+
+    /* Compute the socket now. */
     this->compute_output_and_forward(from_socket);
-    return value_by_input_.pop(&socket_to_compute);
+    return {value_by_input_.pop(key)};
   }
 
   void compute_output_and_forward(const DOutputSocket &socket_to_compute)
@@ -302,8 +323,14 @@ class GeometryNodesEvaluator {
     GValueMap<StringRef> node_inputs_map{allocator_};
     for (const DInputSocket *input_socket : node.inputs()) {
       if (input_socket->is_available()) {
-        GMutablePointer value = this->get_input_value(*input_socket);
-        node_inputs_map.add_new_direct(input_socket->identifier(), value);
+        Vector<GMutablePointer> values = this->get_input_values(*input_socket);
+        for (int i = 0; i < values.size(); ++i) {
+          /* Values from Multi Input Sockets are stored in input map with the format
+           * <identifier>[<index>]. */
+          blender::StringRefNull key = allocator_.copy_string(
+              input_socket->identifier() + (i > 0 ? ("[" + std::to_string(i)) + "]" : ""));
+          node_inputs_map.add_new_direct(key, std::move(values[i]));
+        }
       }
     }
 
@@ -393,13 +420,15 @@ class GeometryNodesEvaluator {
 
   void forward_to_inputs(const DOutputSocket &from_socket, GMutablePointer value_to_forward)
   {
+    /* For all sockets that are linked with the from_socket push the value to their node. */
     Span<const DInputSocket *> to_sockets_all = from_socket.linked_sockets();
 
     const CPPType &from_type = *value_to_forward.type();
-
     Vector<const DInputSocket *> to_sockets_same_type;
     for (const DInputSocket *to_socket : to_sockets_all) {
       const CPPType &to_type = *blender::nodes::socket_cpp_type_get(*to_socket->typeinfo());
+      const std::pair<const DInputSocket *, const DOutputSocket *> key = std::make_pair(
+          to_socket, &from_socket);
       if (from_type == to_type) {
         to_sockets_same_type.append(to_socket);
       }
@@ -411,7 +440,7 @@ class GeometryNodesEvaluator {
         else {
           to_type.copy_to_uninitialized(to_type.default_value(), buffer);
         }
-        value_by_input_.add_new(to_socket, GMutablePointer{to_type, buffer});
+        add_value_to_input_socket(key, GMutablePointer{to_type, buffer});
       }
     }
 
@@ -422,23 +451,35 @@ class GeometryNodesEvaluator {
     else if (to_sockets_same_type.size() == 1) {
       /* This value is only used on one input socket, no need to copy it. */
       const DInputSocket *to_socket = to_sockets_same_type[0];
-      value_by_input_.add_new(to_socket, value_to_forward);
+      const std::pair<const DInputSocket *, const DOutputSocket *> key = std::make_pair(
+          to_socket, &from_socket);
+
+      add_value_to_input_socket(key, value_to_forward);
     }
     else {
       /* Multiple inputs use the value, make a copy for every input except for one. */
       const DInputSocket *first_to_socket = to_sockets_same_type[0];
       Span<const DInputSocket *> other_to_sockets = to_sockets_same_type.as_span().drop_front(1);
       const CPPType &type = *value_to_forward.type();
-
-      value_by_input_.add_new(first_to_socket, value_to_forward);
+      const std::pair<const DInputSocket *, const DOutputSocket *> first_key = std::make_pair(
+          first_to_socket, &from_socket);
+      add_value_to_input_socket(first_key, value_to_forward);
       for (const DInputSocket *to_socket : other_to_sockets) {
+        const std::pair<const DInputSocket *, const DOutputSocket *> key = std::make_pair(
+            to_socket, &from_socket);
         void *buffer = allocator_.allocate(type.size(), type.alignment());
         type.copy_to_uninitialized(value_to_forward.get(), buffer);
-        value_by_input_.add_new(to_socket, GMutablePointer{type, buffer});
+        add_value_to_input_socket(key, GMutablePointer{type, buffer});
       }
     }
   }
 
+  void add_value_to_input_socket(const std::pair<const DInputSocket *, const DOutputSocket *> key,
+                                 GMutablePointer value)
+  {
+    value_by_input_.add_new(key, value);
+  }
+
   GMutablePointer get_unlinked_input_value(const DInputSocket &socket)
   {
     bNodeSocket *bsocket;