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

8 files changed, 207 insertions, 0 deletions

diff --git a/source/blender/gpu/shaders/compositor/compositor_convert.glsl b/source/blender/gpu/shaders/compositor/compositor_convert.glsl
new file mode 100644
index 00000000000..044fb057ca5
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/compositor_convert.glsl
@@ -0,0 +1,8 @@
+#pragma BLENDER_REQUIRE(gpu_shader_compositor_texture_utilities.glsl)
+
+void main()
+{
+  ivec2 texel = ivec2(gl_GlobalInvocationID.xy);
+  vec4 value = texture_load(input_tx, texel);
+  imageStore(output_img, texel, CONVERT_EXPRESSION(value));
+}
diff --git a/source/blender/gpu/shaders/compositor/compositor_realize_on_domain.glsl b/source/blender/gpu/shaders/compositor/compositor_realize_on_domain.glsl
new file mode 100644
index 00000000000..b2961d07219
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/compositor_realize_on_domain.glsl
@@ -0,0 +1,25 @@
+#pragma BLENDER_REQUIRE(gpu_shader_compositor_texture_utilities.glsl)
+
+void main()
+{
+  ivec2 texel = ivec2(gl_GlobalInvocationID.xy);
+
+  /* First, transform the input image by transforming the domain coordinates with the inverse of
+   * input image's transformation. The inverse transformation is an affine matrix and thus the
+   * coordinates should be in homogeneous coordinates.  */
+  vec2 coordinates = (mat3(inverse_transformation) * vec3(texel, 1.0)).xy;
+
+  /* Since an input image with an identity transformation is supposed to be centered in the domain,
+   * we subtract the offset between the lower left corners of the input image and the domain, which
+   * is half the difference between their sizes, because the difference in size is on both sides of
+   * the centered image. */
+  ivec2 domain_size = imageSize(domain_img);
+  ivec2 input_size = texture_size(input_tx);
+  vec2 offset = (domain_size - input_size) / 2.0;
+
+  /* Subtract the offset and divide by the input image size to get the relevant coordinates into
+   * the sampler's expected [0, 1] range. */
+  vec2 normalized_coordinates = (coordinates - offset) / input_size;
+
+  imageStore(domain_img, texel, texture(input_tx, normalized_coordinates));
+}
diff --git a/source/blender/gpu/shaders/compositor/infos/compositor_convert_info.hh b/source/blender/gpu/shaders/compositor/infos/compositor_convert_info.hh
new file mode 100644
index 00000000000..235525b582b
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/infos/compositor_convert_info.hh
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "gpu_shader_create_info.hh"
+
+GPU_SHADER_CREATE_INFO(compositor_convert_shared)
+    .local_group_size(16, 16)
+    .sampler(0, ImageType::FLOAT_2D, "input_tx")
+    .typedef_source("gpu_shader_compositor_type_conversion.glsl")
+    .compute_source("compositor_convert.glsl");
+
+GPU_SHADER_CREATE_INFO(compositor_convert_float_to_vector)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4(vec3_from_float(value.x), 0.0)")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_float_to_color)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4_from_float(value.x)")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_color_to_float)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_R16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4(float_from_vec4(value), vec3(0.0))")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_color_to_vector)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4(vec3_from_vec4(value), 0.0)")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_vector_to_float)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_R16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4(float_from_vec3(value.xyz), vec3(0.0))")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_vector_to_color)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4_from_vec3(value.xyz)")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_extract_alpha_from_color)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_R16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4(value.a, vec3(0.0))")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_color_to_half_color)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "value")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_convert_float_to_half_float)
+    .additional_info("compositor_convert_shared")
+    .image(0, GPU_R16F, Qualifier::WRITE, ImageType::FLOAT_2D, "output_img")
+    .define("CONVERT_EXPRESSION(value)", "vec4(value.r, vec3(0.0))")
+    .do_static_compilation(true);
diff --git a/source/blender/gpu/shaders/compositor/infos/compositor_realize_on_domain_info.hh b/source/blender/gpu/shaders/compositor/infos/compositor_realize_on_domain_info.hh
new file mode 100644
index 00000000000..4528649ae98
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/infos/compositor_realize_on_domain_info.hh
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "gpu_shader_create_info.hh"
+
+GPU_SHADER_CREATE_INFO(compositor_realize_on_domain_shared)
+    .local_group_size(16, 16)
+    .push_constant(Type::MAT4, "inverse_transformation")
+    .sampler(0, ImageType::FLOAT_2D, "input_tx")
+    .compute_source("compositor_realize_on_domain.glsl");
+
+GPU_SHADER_CREATE_INFO(compositor_realize_on_domain_color)
+    .additional_info("compositor_realize_on_domain_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "domain_img")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_realize_on_domain_vector)
+    .additional_info("compositor_realize_on_domain_shared")
+    .image(0, GPU_RGBA16F, Qualifier::WRITE, ImageType::FLOAT_2D, "domain_img")
+    .do_static_compilation(true);
+
+GPU_SHADER_CREATE_INFO(compositor_realize_on_domain_float)
+    .additional_info("compositor_realize_on_domain_shared")
+    .image(0, GPU_R16F, Qualifier::WRITE, ImageType::FLOAT_2D, "domain_img")
+    .do_static_compilation(true);
diff --git a/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_main.glsl b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_main.glsl
new file mode 100644
index 00000000000..27624223dbc
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_main.glsl
@@ -0,0 +1,7 @@
+/* The compute shader that will be dispatched by the compositor ShaderOperation. It just calls the
+ * evaluate function that will be dynamically generated and appended to this shader in the
+ * ShaderOperation::generate_code method. */
+void main()
+{
+  evaluate();
+}
diff --git a/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_store_output.glsl b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_store_output.glsl
new file mode 100644
index 00000000000..7fba26907b5
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_store_output.glsl
@@ -0,0 +1,26 @@
+/* The following functions are called to store the given value in the output identified by the
+ * given ID. The ID is an unsigned integer that is encoded in a float, so floatBitsToUint is called
+ * to get the actual identifier. The functions have an output value as their last argument that is
+ * used to establish an output link that is then used to track the nodes that contribute to the
+ * output of the compositor node tree.
+ *
+ * The store_[float|vector|color] functions are dynamically generated in
+ * ShaderOperation::generate_code_for_outputs. */
+
+void node_compositor_store_output_float(const float id, float value, out float out_value)
+{
+  store_float(floatBitsToUint(id), value);
+  out_value = value;
+}
+
+void node_compositor_store_output_vector(const float id, vec3 vector, out vec3 out_vector)
+{
+  store_vector(floatBitsToUint(id), vector);
+  out_vector = vector;
+}
+
+void node_compositor_store_output_color(const float id, vec4 color, out vec4 out_color)
+{
+  store_color(floatBitsToUint(id), color);
+  out_color = color;
+}
diff --git a/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_texture_utilities.glsl b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_texture_utilities.glsl
new file mode 100644
index 00000000000..00e9a391097
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_texture_utilities.glsl
@@ -0,0 +1,25 @@
+/* A shorthand for 1D textureSize with a zero LOD. */
+int texture_size(sampler1D sampler)
+{
+  return textureSize(sampler, 0);
+}
+
+/* A shorthand for 1D texelFetch with zero LOD and bounded access clamped to border. */
+vec4 texture_load(sampler1D sampler, int x)
+{
+  const int texture_bound = texture_size(sampler) - 1;
+  return texelFetch(sampler, clamp(x, 0, texture_bound), 0);
+}
+
+/* A shorthand for 2D textureSize with a zero LOD. */
+ivec2 texture_size(sampler2D sampler)
+{
+  return textureSize(sampler, 0);
+}
+
+/* A shorthand for 2D texelFetch with zero LOD and bounded access clamped to border. */
+vec4 texture_load(sampler2D sampler, ivec2 texel)
+{
+  const ivec2 texture_bounds = texture_size(sampler) - ivec2(1);
+  return texelFetch(sampler, clamp(texel, ivec2(0), texture_bounds), 0);
+}
diff --git a/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_type_conversion.glsl b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_type_conversion.glsl
new file mode 100644
index 00000000000..75c76fd7341
--- /dev/null
+++ b/source/blender/gpu/shaders/compositor/library/gpu_shader_compositor_type_conversion.glsl
@@ -0,0 +1,29 @@
+float float_from_vec4(vec4 vector)
+{
+  return dot(vector.rgb, vec3(1.0)) / 3.0;
+}
+
+float float_from_vec3(vec3 vector)
+{
+  return dot(vector, vec3(1.0)) / 3.0;
+}
+
+vec3 vec3_from_vec4(vec4 vector)
+{
+  return vector.rgb;
+}
+
+vec3 vec3_from_float(float value)
+{
+  return vec3(value);
+}
+
+vec4 vec4_from_vec3(vec3 vector)
+{
+  return vec4(vector, 1.0);
+}
+
+vec4 vec4_from_float(float value)
+{
+  return vec4(vec3(value), 1.0);
+}