Realtime Compositor: Add evaluator and engine

This patch adds the core realtime compositor evaluator as well as a
compositor draw engine powered by the evaluator that operates in the
viewport. The realtime compositor is a new GPU accelerated compositor
that will be used to power the viewport compositor imminently as well as
the existing compositor in the future.

This patch only adds the evaluator and engine as an experimental
feature, the implementation of the nodes themselves will be committed
separately.

See T99210.

Differential Revision: https://developer.blender.org/D15206

Reviewed By: Clement Foucault

1 files changed, 201 insertions, 0 deletions

diff --git a/source/blender/compositor/realtime_compositor/intern/operation.cc b/source/blender/compositor/realtime_compositor/intern/operation.cc
new file mode 100644
index 00000000000..42dd5aeebe8
--- /dev/null
+++ b/source/blender/compositor/realtime_compositor/intern/operation.cc
@@ -0,0 +1,201 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <limits>
+#include <memory>
+
+#include "BLI_map.hh"
+#include "BLI_string_ref.hh"
+#include "BLI_vector.hh"
+
+#include "COM_context.hh"
+#include "COM_conversion_operation.hh"
+#include "COM_domain.hh"
+#include "COM_input_descriptor.hh"
+#include "COM_operation.hh"
+#include "COM_realize_on_domain_operation.hh"
+#include "COM_reduce_to_single_value_operation.hh"
+#include "COM_result.hh"
+#include "COM_simple_operation.hh"
+#include "COM_static_shader_manager.hh"
+#include "COM_texture_pool.hh"
+
+namespace blender::realtime_compositor {
+
+Operation::Operation(Context &context) : context_(context)
+{
+}
+
+Operation::~Operation() = default;
+
+void Operation::evaluate()
+{
+  evaluate_input_processors();
+
+  reset_results();
+
+  execute();
+
+  release_inputs();
+}
+
+Result &Operation::get_result(StringRef identifier)
+{
+  return results_.lookup(identifier);
+}
+
+void Operation::map_input_to_result(StringRef identifier, Result *result)
+{
+  results_mapped_to_inputs_.add_new(identifier, result);
+}
+
+Domain Operation::compute_domain()
+{
+  /* Default to an identity domain in case no domain input was found, most likely because all
+   * inputs are single values. */
+  Domain operation_domain = Domain::identity();
+  int current_domain_priority = std::numeric_limits<int>::max();
+
+  /* Go over the inputs and find the domain of the non single value input with the highest domain
+   * priority. */
+  for (StringRef identifier : input_descriptors_.keys()) {
+    const Result &result = get_input(identifier);
+    const InputDescriptor &descriptor = get_input_descriptor(identifier);
+
+    /* A single value input can't be a domain input. */
+    if (result.is_single_value() || descriptor.expects_single_value) {
+      continue;
+    }
+
+    /* Notice that the lower the domain priority value is, the higher the priority is, hence the
+     * less than comparison. */
+    if (descriptor.domain_priority < current_domain_priority) {
+      operation_domain = result.domain();
+      current_domain_priority = descriptor.domain_priority;
+    }
+  }
+
+  return operation_domain;
+}
+
+void Operation::add_and_evaluate_input_processors()
+{
+  /* Each input processor type is added to all inputs entirely before the next type. This is done
+   * because the construction of the input processors may depend on the result of previous input
+   * processors for all inputs. For instance, the realize on domain input processor considers the
+   * value of all inputs, so previous input processors for all inputs needs to be added and
+   * evaluated first.  */
+
+  for (const StringRef &identifier : results_mapped_to_inputs_.keys()) {
+    SimpleOperation *single_value = ReduceToSingleValueOperation::construct_if_needed(
+        context(), get_input(identifier));
+    add_and_evaluate_input_processor(identifier, single_value);
+  }
+
+  for (const StringRef &identifier : results_mapped_to_inputs_.keys()) {
+    SimpleOperation *conversion = ConversionOperation::construct_if_needed(
+        context(), get_input(identifier), get_input_descriptor(identifier));
+    add_and_evaluate_input_processor(identifier, conversion);
+  }
+
+  for (const StringRef &identifier : results_mapped_to_inputs_.keys()) {
+    SimpleOperation *realize_on_domain = RealizeOnDomainOperation::construct_if_needed(
+        context(), get_input(identifier), get_input_descriptor(identifier), compute_domain());
+    add_and_evaluate_input_processor(identifier, realize_on_domain);
+  }
+}
+
+void Operation::add_and_evaluate_input_processor(StringRef identifier, SimpleOperation *processor)
+{
+  /* Allow null inputs to facilitate construct_if_needed pattern of addition. For instance, see the
+   * implementation of the add_and_evaluate_input_processors method. */
+  if (!processor) {
+    return;
+  }
+
+  ProcessorsVector &processors = input_processors_.lookup_or_add_default(identifier);
+
+  /* Get the result that should serve as the input for the processor. This is either the result
+   * mapped to the input or the result of the last processor depending on whether this is the first
+   * processor or not. */
+  Result &result = processors.is_empty() ? get_input(identifier) : processors.last()->get_result();
+
+  /* Map the input result of the processor and add it to the processors vector. */
+  processor->map_input_to_result(&result);
+  processors.append(std::unique_ptr<SimpleOperation>(processor));
+
+  /* Switch the result mapped to the input to be the output result of the processor. */
+  switch_result_mapped_to_input(identifier, &processor->get_result());
+
+  processor->evaluate();
+}
+
+Result &Operation::get_input(StringRef identifier) const
+{
+  return *results_mapped_to_inputs_.lookup(identifier);
+}
+
+void Operation::switch_result_mapped_to_input(StringRef identifier, Result *result)
+{
+  results_mapped_to_inputs_.lookup(identifier) = result;
+}
+
+void Operation::populate_result(StringRef identifier, Result result)
+{
+  results_.add_new(identifier, result);
+}
+
+void Operation::declare_input_descriptor(StringRef identifier, InputDescriptor descriptor)
+{
+  input_descriptors_.add_new(identifier, descriptor);
+}
+
+InputDescriptor &Operation::get_input_descriptor(StringRef identifier)
+{
+  return input_descriptors_.lookup(identifier);
+}
+
+Context &Operation::context()
+{
+  return context_;
+}
+
+TexturePool &Operation::texture_pool() const
+{
+  return context_.texture_pool();
+}
+
+StaticShaderManager &Operation::shader_manager() const
+{
+  return context_.shader_manager();
+}
+
+void Operation::evaluate_input_processors()
+{
+  if (!input_processors_added_) {
+    add_and_evaluate_input_processors();
+    input_processors_added_ = true;
+    return;
+  }
+
+  for (const ProcessorsVector &processors : input_processors_.values()) {
+    for (const std::unique_ptr<SimpleOperation> &processor : processors) {
+      processor->evaluate();
+    }
+  }
+}
+
+void Operation::reset_results()
+{
+  for (Result &result : results_.values()) {
+    result.reset();
+  }
+}
+
+void Operation::release_inputs()
+{
+  for (Result *result : results_mapped_to_inputs_.values()) {
+    result->release();
+  }
+}
+
+}  // namespace blender::realtime_compositor