--initial commit; Make fallback material noticeable

--make material color magenta
--add flag that this material is a fallback for an object lacking any other materials
--remove default phong material function; specifying phong shader to use should be sufficient for depth sensor.

src/esp/assets/ResourceManager.cpp

@@ -2162,7 +2162,7 @@ Mn::Trade::MaterialData createUniversalMaterial(
   Mn::Trade::MaterialData newMaterialData{flags, std::move(newAttributes)};
 
   return newMaterialData;
-}  // namespace
+}  // createUniversalMaterial
 
 }  // namespace
 
@@ -2181,23 +2181,13 @@ Mn::Trade::MaterialData ResourceManager::buildDefaultMaterial() {
   return materialData;
 }  // ResourceManager::buildDefaultMaterial
 
-// Specifically for building materials that relied on old defaults
-Mn::Trade::MaterialData ResourceManager::buildDefaultPhongMaterial() {
-  Mn::Trade::MaterialData materialData{
-      Mn::Trade::MaterialType::Phong,
-      {{Mn::Trade::MaterialAttribute::AmbientColor, Mn::Color4{0.1}},
-       {Mn::Trade::MaterialAttribute::DiffuseColor, Mn::Color4{0.7 * 0.175}},
-       {Mn::Trade::MaterialAttribute::SpecularColor, Mn::Color4{0.2 * 0.175}},
-       {Mn::Trade::MaterialAttribute::Shininess, 80.0f}}};
-  return materialData;
-}  // ResourceManager::buildDefaultPhongMaterial
-
 Mn::Trade::MaterialData ResourceManager::setMaterialDefaultUserAttributes(
     const Mn::Trade::MaterialData& material,
     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",
@@ -2209,6 +2199,8 @@ 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), {}});
@@ -2308,17 +2300,28 @@ void ResourceManager::initDefaultMaterials() {
                                               std::move(vertIdMaterialData));
 
   // Build default material for fallback material
-  // TODO: Skinning only works with Phong.
+  Mn::Trade::MaterialData fallbackMaterial = buildDefaultMaterial();
+  // 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};
+  // TODO: Currently skinning only works with Phong.
   //       The default material is loaded when the simulation is only using
   //       depth sensors. We set the fallback as Phong to avoid breaking
   //       skinning with depth sensors.
-  auto fallBackMaterial = buildDefaultPhongMaterial();
-  // Set expected user-defined attributes
-  fallBackMaterial = setMaterialDefaultUserAttributes(
-      fallBackMaterial, ObjectInstanceShaderType::Phong);
+  // Set expected user-defined attributes - specify Phong shader to use
+  fallbackMaterial = setMaterialDefaultUserAttributes(
+      fallbackMaterial, ObjectInstanceShaderType::Phong, false, false, -1,
+      true);
   // Add to shaderManager as fallback material
   shaderManager_.setFallback<Mn::Trade::MaterialData>(
-      std::move(fallBackMaterial));
+      std::move(fallbackMaterial));
 }  // ResourceManager::initDefaultMaterials
 
 void ResourceManager::loadMaterials(Importer& importer,

src/esp/assets/ResourceManager.h

@@ -721,11 +721,6 @@ class ResourceManager {
    */
   Mn::Trade::MaterialData buildDefaultMaterial();
 
-  /**
-   * @brief Build a default Phong material.
-   */
-  Mn::Trade::MaterialData buildDefaultPhongMaterial();
-
   /**
    * @brief Define and set user-defined attributes for the passed
    * @ref Magnum::Trade::MaterialData.
@@ -739,14 +734,17 @@ 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