Compositor: Support implicit conversion across 2D vectors

This patch adds the necessary functions needed to support implicit
conversion in GPU execution across 2D vectors in the compositor.

Pull Request: https://projects.blender.org/blender/blender/pulls/147975

source/blender/compositor/intern/shader_operation.cc

@@ -531,7 +531,7 @@ void ShaderOperation::generate_code(void *thunk,
   shader_create_info.local_group_size(16, 16);
 
   /* Add implementation for implicit conversion operations inserted by the code generator. This
-   * file should include the functions [float|vec3|vec4]_from_[float|vec3|vec4]. */
+   * file should include the functions [float|vec2|vec3|vec4]_from_[float|vec2|vec3|vec4]. */
   shader_create_info.typedef_source("gpu_shader_compositor_type_conversion.glsl");
 
   /* The source shader is a compute shader with a main function that calls the dynamically

source/blender/compositor/shaders/library/gpu_shader_compositor_type_conversion.glsl

@@ -330,9 +330,34 @@ float float_from_vec3(float3 vector)
   return dot(vector, float3(1.0f)) / 3.0f;
 }
 
+float float_from_vec2(float2 vector)
+{
+  return dot(vector, float2(1.0f)) / 2.0f;
+}
+
+float2 vec2_from_vec4(float4 vector)
+{
+  return vector.xy;
+}
+
+float2 vec2_from_vec3(float3 vector)
+{
+  return vector.xy;
+}
+
+float2 vec2_from_float(float value)
+{
+  return float2(value);
+}
+
 float3 vec3_from_vec4(float4 vector)
 {
-  return vector.rgb;
+  return vector.xyz;
+}
+
+float3 vec3_from_vec2(float2 vector)
+{
+  return float3(vector, 0.0f);
 }
 
 float3 vec3_from_float(float value)
@@ -340,6 +365,11 @@ float3 vec3_from_float(float value)
   return float3(value);
 }
 
+float4 vec4_from_vec2(float2 vector)
+{
+  return float4(vector, 0.0f, 1.0f);
+}
+
 float4 vec4_from_vec3(float3 vector)
 {
   return float4(vector, 1.0f);