Materials: add custom object properties as uniform attributes.

This patch allows the user to type a property name into the
Attribute node, which will then output the value of the property
for each individual object, allowing to e.g. customize shaders
by object without duplicating the shader.

In order to make supporting this easier for Eevee, it is necessary
to explicitly choose whether the attribute is varying or uniform
via a dropdown option of the Attribute node. The dropdown also
allows choosing whether instancing should be taken into account.

The Cycles design treats all attributes as one common namespace,
so the Blender interface converts the enum to a name prefix that
can't be entered using keyboard.

In Eevee, the attributes are provided to the shader via a UBO indexed
with resource_id, similar to the existing Object Info data. Unlike it,
however, it is necessary to maintain a separate buffer for every
requested combination of attributes.

This is done using a hash table with the attribute set as the key,
as it is expected that technically different but similar materials
may use the same set of attributes. In addition, in order to minimize
wasted memory, a sparse UBO pool is implemented, so that chunks that
don't contain any data don't have to be allocated.

The back-end Cycles code is already refactored and committed by Brecht.

Differential Revision: https://developer.blender.org/D2057

1 files changed, 149 insertions, 0 deletions

diff --git a/source/blender/gpu/intern/gpu_node_graph.c b/source/blender/gpu/intern/gpu_node_graph.c
index fdf8ba172cb..2a2a51e32b3 100644
--- a/source/blender/gpu/intern/gpu_node_graph.c
+++ b/source/blender/gpu/intern/gpu_node_graph.c
@@ -137,6 +137,10 @@ static void gpu_node_input_link(GPUNode *node, GPUNodeLink *link, const eGPUType
        * can happen if mixing the generic Attribute node with specialized ones. */
       CLAMP_MIN(input->attr->gputype, type);
       break;
+    case GPU_NODE_LINK_UNIFORM_ATTR:
+      input->source = GPU_SOURCE_UNIFORM_ATTR;
+      input->uniform_attr = link->uniform_attr;
+      break;
     case GPU_NODE_LINK_CONSTANT:
       input->source = (type == GPU_CLOSURE) ? GPU_SOURCE_STRUCT : GPU_SOURCE_CONSTANT;
       break;
@@ -262,8 +266,90 @@ static void gpu_node_output(GPUNode *node, const eGPUType type, GPUNodeLink **li
   BLI_addtail(&node->outputs, output);
 }
 
+/* Uniform Attribute Functions */
+
+static int uniform_attr_sort_cmp(const void *a, const void *b)
+{
+  const GPUUniformAttr *attr_a = a, *attr_b = b;
+
+  int cmps = strcmp(attr_a->name, attr_b->name);
+  if (cmps != 0) {
+    return cmps > 0 ? 1 : 0;
+  }
+
+  return (attr_a->use_dupli && !attr_b->use_dupli);
+}
+
+static unsigned int uniform_attr_list_hash(const void *key)
+{
+  const GPUUniformAttrList *attrs = key;
+  return attrs->hash_code;
+}
+
+static bool uniform_attr_list_cmp(const void *a, const void *b)
+{
+  const GPUUniformAttrList *set_a = a, *set_b = b;
+
+  if (set_a->hash_code != set_b->hash_code || set_a->count != set_b->count) {
+    return true;
+  }
+
+  GPUUniformAttr *attr_a = set_a->list.first, *attr_b = set_b->list.first;
+
+  for (; attr_a && attr_b; attr_a = attr_a->next, attr_b = attr_b->next) {
+    if (!STREQ(attr_a->name, attr_b->name) || attr_a->use_dupli != attr_b->use_dupli) {
+      return true;
+    }
+  }
+
+  return attr_a || attr_b;
+}
+
+struct GHash *GPU_uniform_attr_list_hash_new(const char *info)
+{
+  return BLI_ghash_new(uniform_attr_list_hash, uniform_attr_list_cmp, info);
+}
+
+void GPU_uniform_attr_list_copy(GPUUniformAttrList *dest, GPUUniformAttrList *src)
+{
+  dest->count = src->count;
+  dest->hash_code = src->hash_code;
+  BLI_duplicatelist(&dest->list, &src->list);
+}
+
+void GPU_uniform_attr_list_free(GPUUniformAttrList *set)
+{
+  set->count = 0;
+  set->hash_code = 0;
+  BLI_freelistN(&set->list);
+}
+
+void gpu_node_graph_finalize_uniform_attrs(GPUNodeGraph *graph)
+{
+  GPUUniformAttrList *attrs = &graph->uniform_attrs;
+  BLI_assert(attrs->count == BLI_listbase_count(&attrs->list));
+
+  /* Sort the attributes by name to ensure a stable order. */
+  BLI_listbase_sort(&attrs->list, uniform_attr_sort_cmp);
+
+  /* Compute the indices and the hash code. */
+  int next_id = 0;
+  attrs->hash_code = 0;
+
+  LISTBASE_FOREACH (GPUUniformAttr *, attr, &attrs->list) {
+    attr->id = next_id++;
+
+    attrs->hash_code ^= BLI_ghashutil_strhash_p(attr->name);
+
+    if (attr->use_dupli) {
+      attrs->hash_code ^= BLI_ghashutil_uinthash(attr->id);
+    }
+  }
+}
+
 /* Attributes and Textures */
 
+/** Add a new varying attribute of given type and name. Returns NULL if out of slots. */
 static GPUMaterialAttribute *gpu_node_graph_add_attribute(GPUNodeGraph *graph,
                                                           CustomDataType type,
                                                           const char *name)
@@ -299,6 +385,38 @@ static GPUMaterialAttribute *gpu_node_graph_add_attribute(GPUNodeGraph *graph,
   return attr;
 }
 
+/** Add a new uniform attribute of given type and name. Returns NULL if out of slots. */
+static GPUUniformAttr *gpu_node_graph_add_uniform_attribute(GPUNodeGraph *graph,
+                                                            const char *name,
+                                                            bool use_dupli)
+{
+  /* Find existing attribute. */
+  GPUUniformAttrList *attrs = &graph->uniform_attrs;
+  GPUUniformAttr *attr = attrs->list.first;
+
+  for (; attr; attr = attr->next) {
+    if (STREQ(attr->name, name) && attr->use_dupli == use_dupli) {
+      break;
+    }
+  }
+
+  /* Add new requested attribute if it's within GPU limits. */
+  if (attr == NULL && attrs->count < GPU_MAX_UNIFORM_ATTR) {
+    attr = MEM_callocN(sizeof(*attr), __func__);
+    STRNCPY(attr->name, name);
+    attr->use_dupli = use_dupli;
+    attr->id = -1;
+    BLI_addtail(&attrs->list, attr);
+    attrs->count++;
+  }
+
+  if (attr != NULL) {
+    attr->users++;
+  }
+
+  return attr;
+}
+
 static GPUMaterialTexture *gpu_node_graph_add_texture(GPUNodeGraph *graph,
                                                       Image *ima,
                                                       ImageUser *iuser,
@@ -372,6 +490,7 @@ GPUNodeLink *GPU_attribute(GPUMaterial *mat, const CustomDataType type, const ch
   GPUNodeGraph *graph = gpu_material_node_graph(mat);
   GPUMaterialAttribute *attr = gpu_node_graph_add_attribute(graph, type, name);
 
+  /* Dummy fallback if out of slots. */
   if (attr == NULL) {
     static const float zero_data[GPU_MAX_CONSTANT_DATA] = {0.0f};
     return GPU_constant(zero_data);
@@ -383,6 +502,23 @@ GPUNodeLink *GPU_attribute(GPUMaterial *mat, const CustomDataType type, const ch
   return link;
 }
 
+GPUNodeLink *GPU_uniform_attribute(GPUMaterial *mat, const char *name, bool use_dupli)
+{
+  GPUNodeGraph *graph = gpu_material_node_graph(mat);
+  GPUUniformAttr *attr = gpu_node_graph_add_uniform_attribute(graph, name, use_dupli);
+
+  /* Dummy fallback if out of slots. */
+  if (attr == NULL) {
+    static const float zero_data[GPU_MAX_CONSTANT_DATA] = {0.0f};
+    return GPU_constant(zero_data);
+  }
+
+  GPUNodeLink *link = gpu_node_link_create();
+  link->link_type = GPU_NODE_LINK_UNIFORM_ATTR;
+  link->uniform_attr = attr;
+  return link;
+}
+
 GPUNodeLink *GPU_constant(const float *num)
 {
   GPUNodeLink *link = gpu_node_link_create();
@@ -619,6 +755,9 @@ static void gpu_inputs_free(ListBase *inputs)
     if (input->source == GPU_SOURCE_ATTR) {
       input->attr->users--;
     }
+    else if (input->source == GPU_SOURCE_UNIFORM_ATTR) {
+      input->uniform_attr->users--;
+    }
     else if (ELEM(input->source, GPU_SOURCE_TEX, GPU_SOURCE_TEX_TILED_MAPPING)) {
       input->texture->users--;
     }
@@ -674,6 +813,7 @@ void gpu_node_graph_free(GPUNodeGraph *graph)
   BLI_freelistN(&graph->volume_grids);
   BLI_freelistN(&graph->textures);
   BLI_freelistN(&graph->attributes);
+  GPU_uniform_attr_list_free(&graph->uniform_attrs);
 }
 
 /* Prune Unused Nodes */
@@ -738,4 +878,13 @@ void gpu_node_graph_prune_unused(GPUNodeGraph *graph)
       BLI_freelinkN(&graph->volume_grids, grid);
     }
   }
+
+  GPUUniformAttrList *uattrs = &graph->uniform_attrs;
+
+  LISTBASE_FOREACH_MUTABLE (GPUUniformAttr *, attr, &uattrs->list) {
+    if (attr->users == 0) {
+      BLI_freelinkN(&uattrs->list, attr);
+      uattrs->count--;
+    }
+  }
 }