Cycles: introduce an ownership system to protect nodes from unwanted deletions.

Problem: the Blender synchronization process creates and tags nodes for usage. It does
this by directly adding and removing nodes from the scene data. If some node is not tagged
as used at the end of a synchronization, it then deletes the node from the scene. This poses
a problem when it comes to supporting procedural nodes who can create other nodes not known
by the Blender synchonization system, which will remove them.

Nodes now have a NodeOwner, which is set after creation. Those owners for now are the Scene
for scene level nodes and ShaderGraph for shader nodes. Instead of creating and deleting
nodes using `new` and `delete` explicitely, we now use `create_node` and `delete_node` methods
found on the owners. `delete_node` will assert that the owner is the right one.

Whenever a scene level node is created or deleted, the appropriate node manager is tagged for
an update, freeing this responsability from BlenderSync or other software exporters.

Concerning BlenderSync, the `id_maps` do not explicitely manipulate scene data anymore, they
only keep track of which nodes are used, employing the scene to create and delete them. To
achieve this, the ParticleSystem is now a Node, although it does not have any sockets.

This is part of T79131.

Reviewed By: #cycles, brecht

Maniphest Tasks: T79131

Differential Revision: https://developer.blender.org/D8540

1 files changed, 26 insertions, 23 deletions

diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index f62d64a7eb3..de32ce53ad7 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -262,9 +262,9 @@ ImageTextureNode::ImageTextureNode() : ImageSlotTextureNode(node_type)
   tiles.push_back(1001);
 }
 
-ShaderNode *ImageTextureNode::clone() const
+ShaderNode *ImageTextureNode::clone(ShaderGraph *graph) const
 {
-  ImageTextureNode *node = new ImageTextureNode(*this);
+  ImageTextureNode *node = graph->create_node<ImageTextureNode>(*this);
   node->handle = handle;
   return node;
 }
@@ -525,9 +525,9 @@ EnvironmentTextureNode::EnvironmentTextureNode() : ImageSlotTextureNode(node_typ
   animated = false;
 }
 
-ShaderNode *EnvironmentTextureNode::clone() const
+ShaderNode *EnvironmentTextureNode::clone(ShaderGraph *graph) const
 {
-  EnvironmentTextureNode *node = new EnvironmentTextureNode(*this);
+  EnvironmentTextureNode *node = graph->create_node<EnvironmentTextureNode>(*this);
   node->handle = handle;
   return node;
 }
@@ -1234,9 +1234,9 @@ IESLightNode::IESLightNode() : TextureNode(node_type)
   slot = -1;
 }
 
-ShaderNode *IESLightNode::clone() const
+ShaderNode *IESLightNode::clone(ShaderGraph *graph) const
 {
-  IESLightNode *node = new IESLightNode(*this);
+  IESLightNode *node = graph->create_node<IESLightNode>(*this);
 
   node->light_manager = NULL;
   node->slot = -1;
@@ -1782,12 +1782,12 @@ PointDensityTextureNode::~PointDensityTextureNode()
 {
 }
 
-ShaderNode *PointDensityTextureNode::clone() const
+ShaderNode *PointDensityTextureNode::clone(ShaderGraph *graph) const
 {
   /* Increase image user count for new node. We need to ensure to not call
    * add_image again, to work around access of freed data on the Blender
    * side. A better solution should be found to avoid this. */
-  PointDensityTextureNode *node = new PointDensityTextureNode(*this);
+  PointDensityTextureNode *node = graph->create_node<PointDensityTextureNode>(*this);
   node->handle = handle; /* TODO: not needed? */
   return node;
 }
@@ -2783,8 +2783,8 @@ void PrincipledBsdfNode::expand(ShaderGraph *graph)
   ShaderInput *emission_in = input("Emission");
   if (emission_in->link || emission != make_float3(0.0f, 0.0f, 0.0f)) {
     /* Create add closure and emission. */
-    AddClosureNode *add = new AddClosureNode();
-    EmissionNode *emission_node = new EmissionNode();
+    AddClosureNode *add = graph->create_node<AddClosureNode>();
+    EmissionNode *emission_node = graph->create_node<EmissionNode>();
     ShaderOutput *new_out = add->output("Closure");
 
     graph->add(add);
@@ -2802,8 +2802,8 @@ void PrincipledBsdfNode::expand(ShaderGraph *graph)
   ShaderInput *alpha_in = input("Alpha");
   if (alpha_in->link || alpha != 1.0f) {
     /* Create mix and transparent BSDF for alpha transparency. */
-    MixClosureNode *mix = new MixClosureNode();
-    TransparentBsdfNode *transparent = new TransparentBsdfNode();
+    MixClosureNode *mix = graph->create_node<MixClosureNode>();
+    TransparentBsdfNode *transparent = graph->create_node<TransparentBsdfNode>();
 
     graph->add(mix);
     graph->add(transparent);
@@ -4475,7 +4475,7 @@ void VolumeInfoNode::expand(ShaderGraph *graph)
 {
   ShaderOutput *color_out = output("Color");
   if (!color_out->links.empty()) {
-    AttributeNode *attr = new AttributeNode();
+    AttributeNode *attr = graph->create_node<AttributeNode>();
     attr->attribute = "color";
     graph->add(attr);
     graph->relink(color_out, attr->output("Color"));
@@ -4483,7 +4483,7 @@ void VolumeInfoNode::expand(ShaderGraph *graph)
 
   ShaderOutput *density_out = output("Density");
   if (!density_out->links.empty()) {
-    AttributeNode *attr = new AttributeNode();
+    AttributeNode *attr = graph->create_node<AttributeNode>();
     attr->attribute = "density";
     graph->add(attr);
     graph->relink(density_out, attr->output("Fac"));
@@ -4491,7 +4491,7 @@ void VolumeInfoNode::expand(ShaderGraph *graph)
 
   ShaderOutput *flame_out = output("Flame");
   if (!flame_out->links.empty()) {
-    AttributeNode *attr = new AttributeNode();
+    AttributeNode *attr = graph->create_node<AttributeNode>();
     attr->attribute = "flame";
     graph->add(attr);
     graph->relink(flame_out, attr->output("Fac"));
@@ -4499,7 +4499,7 @@ void VolumeInfoNode::expand(ShaderGraph *graph)
 
   ShaderOutput *temperature_out = output("Temperature");
   if (!temperature_out->links.empty()) {
-    AttributeNode *attr = new AttributeNode();
+    AttributeNode *attr = graph->create_node<AttributeNode>();
     attr->attribute = "temperature";
     graph->add(attr);
     graph->relink(temperature_out, attr->output("Fac"));
@@ -5768,7 +5768,7 @@ void MapRangeNode::expand(ShaderGraph *graph)
   if (clamp) {
     ShaderOutput *result_out = output("Result");
     if (!result_out->links.empty()) {
-      ClampNode *clamp_node = new ClampNode();
+      ClampNode *clamp_node = graph->create_node<ClampNode>();
       clamp_node->type = NODE_CLAMP_RANGE;
       graph->add(clamp_node);
       graph->relink(result_out, clamp_node->output("Result"));
@@ -6009,7 +6009,7 @@ void MathNode::expand(ShaderGraph *graph)
   if (use_clamp) {
     ShaderOutput *result_out = output("Value");
     if (!result_out->links.empty()) {
-      ClampNode *clamp_node = new ClampNode();
+      ClampNode *clamp_node = graph->create_node<ClampNode>();
       clamp_node->type = NODE_CLAMP_MINMAX;
       clamp_node->min = 0.0f;
       clamp_node->max = 1.0f;
@@ -6337,7 +6337,7 @@ void BumpNode::constant_fold(const ConstantFolder &folder)
 
   if (height_in->link == NULL) {
     if (normal_in->link == NULL) {
-      GeometryNode *geom = new GeometryNode();
+      GeometryNode *geom = folder.graph->create_node<GeometryNode>();
       folder.graph->add(geom);
       folder.bypass(geom->output("Normal"));
     }
@@ -6620,12 +6620,12 @@ OSLNode::~OSLNode()
   delete type;
 }
 
-ShaderNode *OSLNode::clone() const
+ShaderNode *OSLNode::clone(ShaderGraph *graph) const
 {
-  return OSLNode::create(this->inputs.size(), this);
+  return OSLNode::create(graph, this->inputs.size(), this);
 }
 
-OSLNode *OSLNode::create(size_t num_inputs, const OSLNode *from)
+OSLNode *OSLNode::create(ShaderGraph *graph, size_t num_inputs, const OSLNode *from)
 {
   /* allocate space for the node itself and parameters, aligned to 16 bytes
    * assuming that's the most parameter types need */
@@ -6636,7 +6636,9 @@ OSLNode *OSLNode::create(size_t num_inputs, const OSLNode *from)
   memset(node_memory, 0, node_size + inputs_size);
 
   if (!from) {
-    return new (node_memory) OSLNode();
+    OSLNode *node = new (node_memory) OSLNode();
+    node->set_owner(graph);
+    return node;
   }
   else {
     /* copy input default values and node type for cloning */
@@ -6644,6 +6646,7 @@ OSLNode *OSLNode::create(size_t num_inputs, const OSLNode *from)
 
     OSLNode *node = new (node_memory) OSLNode(*from);
     node->type = new NodeType(*(from->type));
+    node->set_owner(from->owner);
     return node;
   }
 }