Fix Cycles blackbody shader not taking into account OpenColorIO config

Keep the existing Rec.709 fit and convert to other colorspace if needed, it
seems accurate enough in practice, and keeps the same performance for the
default case.

1 files changed, 36 insertions, 3 deletions

diff --git a/intern/cycles/scene/shader.cpp b/intern/cycles/scene/shader.cpp
index 8a08f2a5be9..e1af92ea8cf 100644
--- a/intern/cycles/scene/shader.cpp
+++ b/intern/cycles/scene/shader.cpp
@@ -579,6 +579,10 @@ void ShaderManager::device_update_common(Device * /*device*/,
   kfilm->xyz_to_g = float3_to_float4(xyz_to_g);
   kfilm->xyz_to_b = float3_to_float4(xyz_to_b);
   kfilm->rgb_to_y = float3_to_float4(rgb_to_y);
+  kfilm->rec709_to_r = float3_to_float4(rec709_to_r);
+  kfilm->rec709_to_g = float3_to_float4(rec709_to_g);
+  kfilm->rec709_to_b = float3_to_float4(rec709_to_b);
+  kfilm->is_rec709 = is_rec709;
 }
 
 void ShaderManager::device_free_common(Device *, DeviceScene *dscene, Scene *scene)
@@ -740,6 +744,11 @@ float ShaderManager::linear_rgb_to_gray(float3 c)
   return dot(c, rgb_to_y);
 }
 
+float3 ShaderManager::rec709_to_scene_linear(float3 c)
+{
+  return make_float3(dot(rec709_to_r, c), dot(rec709_to_g, c), dot(rec709_to_b, c));
+}
+
 string ShaderManager::get_cryptomatte_materials(Scene *scene)
 {
   string manifest = "{";
@@ -802,11 +811,29 @@ void ShaderManager::init_xyz_transforms()
 {
   /* Default to ITU-BT.709 in case no appropriate transform found.
    * Note XYZ here is defined as having a D65 white point. */
-  xyz_to_r = make_float3(3.2404542f, -1.5371385f, -0.4985314f);
-  xyz_to_g = make_float3(-0.9692660f, 1.8760108f, 0.0415560f);
-  xyz_to_b = make_float3(0.0556434f, -0.2040259f, 1.0572252f);
+  const Transform xyz_to_rec709 = make_transform(3.2404542f,
+                                                 -1.5371385f,
+                                                 -0.4985314f,
+                                                 0.0f,
+                                                 -0.9692660f,
+                                                 1.8760108f,
+                                                 0.0415560f,
+                                                 0.0f,
+                                                 0.0556434f,
+                                                 -0.2040259f,
+                                                 1.0572252f,
+                                                 0.0f);
+
+  xyz_to_r = float4_to_float3(xyz_to_rec709.x);
+  xyz_to_g = float4_to_float3(xyz_to_rec709.y);
+  xyz_to_b = float4_to_float3(xyz_to_rec709.z);
   rgb_to_y = make_float3(0.2126729f, 0.7151522f, 0.0721750f);
 
+  rec709_to_r = make_float3(1.0f, 0.0f, 0.0f);
+  rec709_to_g = make_float3(0.0f, 1.0f, 0.0f);
+  rec709_to_b = make_float3(0.0f, 0.0f, 1.0f);
+  is_rec709 = true;
+
 #ifdef WITH_OCIO
   /* Get from OpenColorO config if it has the required roles. */
   OCIO::ConstConfigRcPtr config = OCIO::GetCurrentConfig();
@@ -857,6 +884,12 @@ void ShaderManager::init_xyz_transforms()
 
   const Transform rgb_to_xyz = transform_inverse(xyz_to_rgb);
   rgb_to_y = float4_to_float3(rgb_to_xyz.y);
+
+  const Transform rec709_to_rgb = xyz_to_rgb * transform_inverse(xyz_to_rec709);
+  rec709_to_r = float4_to_float3(rec709_to_rgb.x);
+  rec709_to_g = float4_to_float3(rec709_to_rgb.y);
+  rec709_to_b = float4_to_float3(rec709_to_rgb.z);
+  is_rec709 = transform_equal_threshold(xyz_to_rgb, xyz_to_rec709, 0.0001f);
 #endif
 }