Add Khronos PBR Neutral tone mapper

A tone mapper designed specifically for PBR color accuracy, to get sRGB
colors in the output render that match as faithfully as possible the input
sRGB baseColor under gray-scale lighting. This is aimed toward product
photography use cases, where the scene is well-exposed and HDR color values
are mostly restricted to small specular highlights.

Fixes #118824: Proposal: add a view transform for Khronos PBR Neutral Tone Mapper

Co-authored-by: Emmett Lalish <elalish@google.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/118936

release/datafiles/colormanagement/config.ocio

@@ -57,6 +57,7 @@ roles:
 displays:
   sRGB:
     - !<View> {name: Standard, colorspace: sRGB}
+    - !<View> {name: Khronos PBR Neutral, colorspace: Khronos PBR Neutral sRGB}
     - !<View> {name: AgX, colorspace: AgX Base sRGB}
     - !<View> {name: Filmic, colorspace: Filmic sRGB}
     - !<View> {name: Filmic Log, colorspace: Filmic Log}
@@ -78,7 +79,7 @@ displays:
     - !<View> {name: False Color, colorspace: AgX False Color Rec.2020}
     - !<View> {name: Raw, colorspace: Non-Color}
 active_displays: [sRGB, Display P3, Rec.1886, Rec.2020]
-active_views: [Standard, AgX, Filmic, Filmic Log, False Color, Raw]
+active_views: [Standard, Khronos PBR Neutral, AgX, Filmic, Filmic Log, False Color, Raw]
 inactive_colorspaces: [Luminance Compensation Rec.2020, Luminance Compensation sRGB, Luminance Compensation P3, AgX False Color Rec.709, AgX False Color P3, AgX False Color Rec.1886, AgX False Color Rec.2020]
 
 colorspaces:
@@ -485,6 +486,21 @@ colorspaces:
         - !<ColorSpaceTransform> {src: Linear CIE-XYZ E, dst: AgX False Color Rec.709}
         - !<ColorSpaceTransform> {src: Rec.1886, dst: Rec.2020}
 
+  - !<ColorSpace>
+    name: Khronos PBR Neutral sRGB
+    family: Khronos PBR Neutral
+    equalitygroup:
+    bitdepth: 32f
+    description: |
+      Khronos PBR Neutral Image Encoding for sRGB Display
+    isdata: false
+    from_scene_reference: !<GroupTransform>
+      children:
+        - !<ColorSpaceTransform> {src: Linear CIE-XYZ E, dst: Linear Rec.709}
+        - !<AllocationTransform> {allocation: lg2, vars: [-9, 10]}
+        - !<FileTransform> {src: pbrNeutral.cube, interpolation: tetrahedral}
+        - !<ColorSpaceTransform> {src: Linear Rec.709, dst: sRGB}
+
 looks:
   - !<Look>
     name: Very High Contrast
@@ -744,4 +760,4 @@ looks:
           style: log
           contrast: {rgb: [0.7, 0.7, 0.7], master: 1}
           saturation: 1.15
-          pivot: {contrast: -0.2}
+          pivot: {contrast: -0.2}

scripts/startup/bl_ui/properties_render.py

@@ -113,7 +113,8 @@ class RENDER_PT_color_management_display_settings(RenderButtonsPanel, Panel):
         col = layout.column(align=True)
         sub = col.row()
         sub.active = (not view.view_transform.startswith("Filmic") and not view.view_transform.startswith("AgX") and not
-                      view.view_transform.startswith("False Color"))
+                      view.view_transform.startswith("False Color") and not 
+                      view.view_transform.startswith("Khronos PBR Neutral"))
         sub.prop(view, "use_hdr_view")