--Set default fallback material handling

src/esp/assets/ResourceManager.cpp

@@ -2138,7 +2138,8 @@ Mn::Trade::MaterialData ResourceManager::setMaterialDefaultUserAttributes(
     ObjectInstanceShaderType shaderTypeToUse,
     bool hasVertObjID,
     bool hasTxtrObjID,
-    int txtrIdx) const {
+    int txtrIdx,
+    bool isFallback) const {
   // New material's attributes
   Cr::Containers::Array<Mn::Trade::MaterialAttributeData> newAttributes;
   arrayAppend(newAttributes, Cr::InPlaceInit, "hasPerVertexObjectId",
@@ -2150,6 +2151,8 @@ Mn::Trade::MaterialData ResourceManager::setMaterialDefaultUserAttributes(
   arrayAppend(newAttributes, Cr::InPlaceInit, "shaderTypeToUse",
               static_cast<int>(shaderTypeToUse));
 
+  arrayAppend(newAttributes, Cr::InPlaceInit, "isFallbackMaterial", isFallback);
+
   Cr::Containers::Optional<Mn::Trade::MaterialData> finalMaterial =
       Mn::MaterialTools::merge(
           material, Mn::Trade::MaterialData{{}, std::move(newAttributes), {}});
@@ -2250,9 +2253,20 @@ void ResourceManager::initDefaultMaterials() {
 
   // Build default material for fallback material
   Mn::Trade::MaterialData fallbackMaterial = buildDefaultMaterial();
-  // Set expected user-defined attributes
+  // Make fallback magenta so visibly obvious
+  fallbackMaterial.mutableAttribute<Mn::Color4>(
+      Mn::Trade::MaterialAttribute::AmbientColor) =
+      Mn::Color4{1.0f, 0.0f, 1.0f, 1.0f};
+  fallbackMaterial.mutableAttribute<Mn::Color4>(
+      Mn::Trade::MaterialAttribute::DiffuseColor) =
+      Mn::Color4{1.0f, 0.0f, 1.0f, 1.0f};
+  fallbackMaterial.mutableAttribute<Mn::Color4>(
+      Mn::Trade::MaterialAttribute::SpecularColor) =
+      Mn::Color4{1.0f, 0.0f, 1.0f, 1.0f};
+  // Set expected user-defined attributes - specify Flat shader to use since
+  // this indicates that the asset did not load a material for some reason.
   fallbackMaterial = setMaterialDefaultUserAttributes(
-      fallbackMaterial, ObjectInstanceShaderType::Flat);
+      fallbackMaterial, ObjectInstanceShaderType::Flat, false, false, -1, true);
   // Add to shaderManager as fallback material
   shaderManager_.setFallback<Mn::Trade::MaterialData>(
       std::move(fallbackMaterial));

src/esp/assets/ResourceManager.h

@@ -751,14 +751,17 @@ class ResourceManager {
    * ids for semantics.
    * @param txtrIdx The absolute index in the @ref textures_ store for the semantic
    * annotation texture.
+   * @param isFallback This material is default fallback material for missing
+   * materials.
    * @return the updated material
    */
   Mn::Trade::MaterialData setMaterialDefaultUserAttributes(
       const Mn::Trade::MaterialData& material,
       ObjectInstanceShaderType shaderTypeToUse,
       bool hasVertObjID = false,
       bool hasTxtrObjID = false,
-      int txtrIdx = -1) const;
+      int txtrIdx = -1,
+      bool isFallback = false) const;
 
   /**
    * @brief Configure the importerManager_ GL Extensions appropriately based on

src/esp/gfx/Drawable.h

@@ -157,6 +157,13 @@ class Drawable : public Magnum::SceneGraph::Drawable3D {
     setMaterialValuesInternal(material, true);
   }
 
+  /**
+   * @brief Whether this drawable has a specified material or was assigned the
+   * default fallback material, meaning the material for the object was either
+   * not loaded or is otherwise missing.
+   */
+  bool getUsesFallbackMaterial() const { return usingFallbackMaterial_; }
+
  private:
   /**
    * Set or change this drawable's @ref Magnum::Trade::MaterialData values from passed material.
@@ -171,6 +178,15 @@ class Drawable : public Magnum::SceneGraph::Drawable3D {
       CORRADE_UNUSED bool reset) {}
 
  protected:
+  /**
+   * @brief Whether this drawable has a specified material or was assigned the
+   * default fallback material, meaning the material for the object was either
+   * not loaded or is otherwise missing.
+   */
+  void setUsesFallbackMaterial(bool _usingFallbackMaterial) {
+    usingFallbackMaterial_ = _usingFallbackMaterial;
+  }
+
   /**
    * @brief resize the jointTransformArray_
    */
@@ -253,6 +269,13 @@ class Drawable : public Magnum::SceneGraph::Drawable3D {
 
   Corrade::Containers::Array<Magnum::Matrix4> jointTransformations_;
 
+  /**
+   * @brief Whether or not this drawable is being rendered using the default
+   * fallback material, which implies either that materials were not loaded, or
+   * else no material existed for the source asset to load.
+   */
+  bool usingFallbackMaterial_ = false;
+
   bool glMeshExists() const { return mesh_ != nullptr; }
 
  private:

src/esp/gfx/GenericDrawable.cpp

@@ -120,6 +120,12 @@ void GenericDrawable::setMaterialValuesInternal(
   if (meshAttributeFlags_ & Drawable::Flag::HasVertexColor) {
     flags_ |= Mn::Shaders::PhongGL::Flag::VertexColor;
   }
+
+  // Set whether this drawable is being rendered using a fallback material; This
+  // would infer that either materials were not loaded or no materials were
+  // found for the source asset
+  setUsesFallbackMaterial(materialData->attribute<bool>("isFallbackMaterial"));
+
   // If not reset then make sure the same shader is used
   if (!reset) {
     flags_ = oldFlags;

src/esp/gfx/PbrDrawable.cpp

@@ -332,6 +332,10 @@ void PbrDrawable::setMaterialValuesInternal(
   if (meshAttributeFlags_ & Drawable::Flag::HasVertexColor) {
     flags_ |= PbrShader::Flag::VertexColor;
   }
+  // Set whether this drawable is being rendered using a fallback material; This
+  // would infer that either materials were not loaded or no materials were
+  // found for the source asset
+  setUsesFallbackMaterial(materialData->attribute<bool>("isFallbackMaterial"));
 
   // Skin support
   (skinData_ != nullptr) ? flags_ |= PbrShader::Flag::SkinnedMesh