[Bf-blender-cvs] [c79b55fc056] master: USD export: add scale and bias for normal maps.

[Michael Kowalski]

Commit: c79b55fc056bbe63818fdb5c697085dd1e0eaceb
Author: Michael Kowalski
Date:   Mon Jan 30 11:32:03 2023 -0500
Branches: master
https://developer.blender.org/rBc79b55fc056bbe63818fdb5c697085dd1e0eaceb

USD export: add scale and bias for normal maps.

Changes authored by Michael B Johnson (drwave).

This addresses the issue in T102911.

Add scale and bias inputs to ensure the normals are
in tangent space [(-1,-1,-1), (1,1,1)].

This is following the convention as set in the USD Spec
(https://graphics.pixar.com/usd/dev/spec_usdpreviewsurface.html).

Differential Revision: https://developer.blender.org/D17072

===================================================================

M	source/blender/io/usd/intern/usd_writer_material.cc

===================================================================

diff --git a/source/blender/io/usd/intern/usd_writer_material.cc b/source/blender/io/usd/intern/usd_writer_material.cc
index 3e2f34b1b1e..1f758bee86a 100644
--- a/source/blender/io/usd/intern/usd_writer_material.cc
+++ b/source/blender/io/usd/intern/usd_writer_material.cc
@@ -61,6 +61,8 @@ static const pxr::TfToken normal("normal", pxr::TfToken::Immortal);
 static const pxr::TfToken ior("ior", pxr::TfToken::Immortal);
 static const pxr::TfToken file("file", pxr::TfToken::Immortal);
 static const pxr::TfToken raw("raw", pxr::TfToken::Immortal);
+static const pxr::TfToken scale("scale", pxr::TfToken::Immortal);
+static const pxr::TfToken bias("bias", pxr::TfToken::Immortal);
 static const pxr::TfToken sRGB("sRGB", pxr::TfToken::Immortal);
 static const pxr::TfToken sourceColorSpace("sourceColorSpace", pxr::TfToken::Immortal);
 static const pxr::TfToken Shader("Shader", pxr::TfToken::Immortal);
@@ -114,6 +116,7 @@ static bNode *traverse_channel(bNodeSocket *input, short target_type);
 template<typename T1, typename T2>
 void create_input(pxr::UsdShadeShader &shader, const InputSpec &spec, const void *value);
 
+void set_normal_texture_range(pxr::UsdShadeShader &usd_shader, const InputSpec &input_spec);
 void create_usd_preview_surface_material(const USDExporterContext &usd_export_context,
                                          Material *material,
                                          pxr::UsdShadeMaterial &usd_material,
@@ -162,6 +165,7 @@ void create_usd_preview_surface_material(const USDExporterContext &usd_export_co
 
       preview_surface.CreateInput(input_spec.input_name, input_spec.input_type)
           .ConnectToSource(created_shader.ConnectableAPI(), input_spec.source_name);
+      set_normal_texture_range(created_shader, input_spec);
     }
     else if (input_spec.set_default_value) {
       /* Set hardcoded value. */
@@ -200,6 +204,40 @@ void create_usd_preview_surface_material(const USDExporterContext &usd_export_co
   }
 }
 
+void set_normal_texture_range(pxr::UsdShadeShader &usd_shader, const InputSpec &input_spec)
+{
+  /* Set the scale and bias for normal map textures
+   * The USD spec requires them to be within the -1 to 1 space
+   * */
+
+  // Only run if this input_spec is for a normal
+  if (input_spec.input_name != usdtokens::normal)
+    return;
+
+  // Make sure this is a texture shader prim
+  pxr::TfToken shader_id;
+  if (!usd_shader.GetIdAttr().Get(&shader_id) || shader_id != usdtokens::uv_texture)
+    return;
+
+  // We should only be setting this if the colorspace is raw. sRGB will not map the same.
+  pxr::TfToken colorspace;
+  auto colorspace_attr = usd_shader.GetInput(usdtokens::sourceColorSpace);
+  if (!colorspace_attr || !colorspace_attr.Get(&colorspace) || colorspace != usdtokens::raw)
+    return;
+
+  // Get or Create the scale attribute and set it
+  auto scale_attr = usd_shader.GetInput(usdtokens::scale);
+  if (!scale_attr)
+    scale_attr = usd_shader.CreateInput(usdtokens::scale, pxr::SdfValueTypeNames->Float4);
+  scale_attr.Set(pxr::GfVec4f(2.0f, 2.0f, 2.0f, 2.0f));
+
+  // Get or Create the bias attribute and set it
+  auto bias_attr = usd_shader.GetInput(usdtokens::bias);
+  if (!bias_attr)
+    bias_attr = usd_shader.CreateInput(usdtokens::bias, pxr::SdfValueTypeNames->Float4);
+  bias_attr.Set(pxr::GfVec4f(-1.0f, -1.0f, -1.0f, -1.0f));
+}
+
 void create_usd_viewport_material(const USDExporterContext &usd_export_context,
                                   Material *material,
                                   pxr::UsdShadeMaterial &usd_material)