From 822b2406943f4bc426b9260a5bba523d65aabe26 Mon Sep 17 00:00:00 2001
From: Adam <adam.v.beili@gmail.com>
Date: Tue, 8 Nov 2022 23:09:50 +0200
Subject: [PATCH 1/9] Support both pbrSpecGlos and materials_specular

---
 code/AssetLib/glTF2/glTF2Asset.h         | 17 +++++++++++++
 code/AssetLib/glTF2/glTF2Asset.inl       | 22 +++++++++++++++-
 code/AssetLib/glTF2/glTF2AssetWriter.h   |  1 +
 code/AssetLib/glTF2/glTF2AssetWriter.inl | 27 ++++++++++++++++++--
 code/AssetLib/glTF2/glTF2Exporter.cpp    | 32 +++++++++++++++++++++---
 code/AssetLib/glTF2/glTF2Exporter.h      |  2 ++
 code/AssetLib/glTF2/glTF2Importer.cpp    | 15 ++++++++++-
 include/assimp/material.h                |  1 +
 8 files changed, 110 insertions(+), 7 deletions(-)

diff --git a/code/AssetLib/glTF2/glTF2Asset.h b/code/AssetLib/glTF2/glTF2Asset.h
index 3becc4d9b..b241a4b59 100644
--- a/code/AssetLib/glTF2/glTF2Asset.h
+++ b/code/AssetLib/glTF2/glTF2Asset.h
@@ -44,6 +44,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * glTF Extensions Support:
  *   KHR_materials_pbrSpecularGlossiness full
+ *   KHR_materials_specular full
  *   KHR_materials_unlit full
  *   KHR_lights_punctual full
  *   KHR_materials_sheen full
@@ -718,6 +719,7 @@ const vec4 defaultBaseColor = { 1, 1, 1, 1 };
 const vec3 defaultEmissiveFactor = { 0, 0, 0 };
 const vec4 defaultDiffuseFactor = { 1, 1, 1, 1 };
 const vec3 defaultSpecularFactor = { 1, 1, 1 };
+const vec3 defaultSpecularColorFactor = { 0, 0, 0 };
 const vec3 defaultSheenFactor = { 0, 0, 0 };
 const vec3 defaultAttenuationColor = { 1, 1, 1 };
 
@@ -761,6 +763,16 @@ struct PbrSpecularGlossiness {
     void SetDefaults();
 };
 
+struct MaterialSpecular {
+    float specularFactor;
+    vec3 specularColorFactor;
+    TextureInfo specularTexture;
+    TextureInfo specularColorTexture;
+
+    MaterialSpecular() { SetDefaults(); }
+    void SetDefaults();
+};
+
 struct MaterialSheen {
     vec3 sheenColorFactor;
     float sheenRoughnessFactor;
@@ -818,6 +830,9 @@ struct Material : public Object {
     //extension: KHR_materials_pbrSpecularGlossiness
     Nullable<PbrSpecularGlossiness> pbrSpecularGlossiness;
 
+    //extension: KHR_materials_specular
+    Nullable<MaterialSpecular> materialSpecular;
+
     //extension: KHR_materials_sheen
     Nullable<MaterialSheen> materialSheen;
 
@@ -1098,6 +1113,7 @@ public:
     //! Keeps info about the enabled extensions
     struct Extensions {
         bool KHR_materials_pbrSpecularGlossiness;
+        bool KHR_materials_specular;
         bool KHR_materials_unlit;
         bool KHR_lights_punctual;
         bool KHR_texture_transform;
@@ -1112,6 +1128,7 @@ public:
 
         Extensions() :
                 KHR_materials_pbrSpecularGlossiness(false), 
+                KHR_materials_specular(false), 
                 KHR_materials_unlit(false), 
                 KHR_lights_punctual(false), 
                 KHR_texture_transform(false), 
diff --git a/code/AssetLib/glTF2/glTF2Asset.inl b/code/AssetLib/glTF2/glTF2Asset.inl
index db47915d6..aaa652dcd 100644
--- a/code/AssetLib/glTF2/glTF2Asset.inl
+++ b/code/AssetLib/glTF2/glTF2Asset.inl
@@ -1236,7 +1236,7 @@ inline void Material::Read(Value &material, Asset &r) {
     ReadMember(material, "alphaCutoff", this->alphaCutoff);
 
     if (Value *extensions = FindObject(material, "extensions")) {
-        if (r.extensionsUsed.KHR_materials_pbrSpecularGlossiness) {
+        if (r.extensionsUsed.KHR_materials_pbrSpecularGlossiness) {  //TODO: Maybe ignore this if KHR_materials_specular is also defined
             if (Value *curPbrSpecularGlossiness = FindObject(*extensions, "KHR_materials_pbrSpecularGlossiness")) {
                 PbrSpecularGlossiness pbrSG;
 
@@ -1249,6 +1249,19 @@ inline void Material::Read(Value &material, Asset &r) {
                 this->pbrSpecularGlossiness = Nullable<PbrSpecularGlossiness>(pbrSG);
             }
         }
+        
+        if (r.extensionsUsed.KHR_materials_specular) {
+            if (Value *curMatSpecular = FindObject(*extensions, "KHR_materials_specular")) {
+                MaterialSpecular specular;
+
+                ReadMember(*curMatSpecular, "specularFactor", specular.specularFactor);
+                ReadTextureProperty(r, *curMatSpecular, "specularTexture", specular.specularTexture);
+                ReadMember(*curMatSpecular, "specularColorFactor", specular.specularColorFactor);
+                ReadTextureProperty(r, *curMatSpecular, "specularColorTexture", specular.specularColorTexture);
+
+                this->materialSpecular = Nullable<MaterialSpecular>(specular);
+            }
+        }
 
         // Extension KHR_texture_transform is handled in ReadTextureProperty
 
@@ -1337,6 +1350,12 @@ inline void PbrSpecularGlossiness::SetDefaults() {
     glossinessFactor = 1.0f;
 }
 
+inline void MaterialSpecular::SetDefaults() {
+    //KHR_materials_specular properties
+    SetVector(specularColorFactor, defaultSpecularColorFactor);
+    specularFactor = 0.f;
+}
+
 inline void MaterialSheen::SetDefaults() {
     //KHR_materials_sheen properties
     SetVector(sheenColorFactor, defaultSheenFactor);
@@ -2018,6 +2037,7 @@ inline void Asset::ReadExtensionsUsed(Document &doc) {
     }
 
     CHECK_EXT(KHR_materials_pbrSpecularGlossiness);
+    CHECK_EXT(KHR_materials_specular);
     CHECK_EXT(KHR_materials_unlit);
     CHECK_EXT(KHR_lights_punctual);
     CHECK_EXT(KHR_texture_transform);
diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.h b/code/AssetLib/glTF2/glTF2AssetWriter.h
index 089a15844..5489ec2d4 100644
--- a/code/AssetLib/glTF2/glTF2AssetWriter.h
+++ b/code/AssetLib/glTF2/glTF2AssetWriter.h
@@ -45,6 +45,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * glTF Extensions Support:
  *   KHR_materials_pbrSpecularGlossiness: full
+ *   KHR_materials_specular: full
  *   KHR_materials_unlit: full
  *   KHR_materials_sheen: full
  *   KHR_materials_clearcoat: full
diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.inl b/code/AssetLib/glTF2/glTF2AssetWriter.inl
index 0be139595..c57603bb0 100644
--- a/code/AssetLib/glTF2/glTF2AssetWriter.inl
+++ b/code/AssetLib/glTF2/glTF2AssetWriter.inl
@@ -418,6 +418,25 @@ namespace glTF2 {
           exts.AddMember("KHR_materials_unlit", unlit, w.mAl);
         }
 
+        if (m.materialSpecular.isPresent) {
+            Value materialSpecular(rapidjson::Type::kObjectType);
+            materialSpecular.SetObject();
+
+            MaterialSpecular &specular = m.materialSpecular.value;
+
+            if (specular.specularFactor != 0.f) {
+                WriteFloat(materialSpecular, specular.specularFactor, "specularFactor", w.mAl);
+                WriteTex(materialSpecular, specular.specularTexture, "specularTexture", w.mAl);
+            }
+            if (specular.specularColorFactor[0] != defaultSpecularColorFactor[0] && specular.specularColorFactor[1] != defaultSpecularColorFactor[1] && specular.specularColorFactor[2] != defaultSpecularColorFactor[2]) {
+                WriteVec(materialSpecular, specular.specularColorFactor, "specularColorFactor", w.mAl);
+                WriteTex(materialSpecular, specular.specularColorTexture, "specularColorTexture", w.mAl);
+            }
+
+            if (!materialSpecular.ObjectEmpty()) {
+                exts.AddMember("KHR_materials_specular", materialSpecular, w.mAl);
+        }
+
         if (m.materialSheen.isPresent) {
             Value materialSheen(rapidjson::Type::kObjectType);
 
@@ -536,7 +555,7 @@ namespace glTF2 {
 
     inline void Write(Value& obj, Mesh& m, AssetWriter& w)
     {
-		/****************** Primitives *******************/
+        /****************** Primitives *******************/
         Value primitives;
         primitives.SetArray();
         primitives.Reserve(unsigned(m.primitives.size()), w.mAl);
@@ -915,6 +934,10 @@ namespace glTF2 {
               exts.PushBack(StringRef("KHR_materials_unlit"), mAl);
             }
 
+            if (this->mAsset.extensionsUsed.KHR_materials_specular) {
+                exts.PushBack(StringRef("KHR_materials_specular"), mAl);
+            }
+
             if (this->mAsset.extensionsUsed.KHR_materials_sheen) {
                 exts.PushBack(StringRef("KHR_materials_sheen"), mAl);
             }
@@ -962,7 +985,7 @@ namespace glTF2 {
         if (d.mObjs.empty()) return;
 
         Value* container = &mDoc;
-		const char* context = "Document";
+        const char* context = "Document";
 
         if (d.mExtId) {
             Value* exts = FindObject(mDoc, "extensions");
diff --git a/code/AssetLib/glTF2/glTF2Exporter.cpp b/code/AssetLib/glTF2/glTF2Exporter.cpp
index 3bfe49fba..15c193d36 100644
--- a/code/AssetLib/glTF2/glTF2Exporter.cpp
+++ b/code/AssetLib/glTF2/glTF2Exporter.cpp
@@ -644,7 +644,10 @@ bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlo
     bool result = false;
     // If has Glossiness, a Specular Color or Specular Texture, use the KHR_materials_pbrSpecularGlossiness extension
     // NOTE: This extension is being considered for deprecation (Dec 2020), may be replaced by KHR_material_specular
-
+    // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
+    if (mat.Get(AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS) != AI_SUCCESS) {
+        return false;
+    }
     if (mat.Get(AI_MATKEY_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) == AI_SUCCESS) {
         result = true;
     } else {
@@ -674,6 +677,24 @@ bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlo
     return result;
 }
 
+bool glTF2Exporter::GetMatSpecular(const aiMaterial &mat, glTF2::MaterialSpecular &specular) {
+    // Specular requires either/or
+    if (GetMatColor(mat, specular.specularColorFactor, AI_MATKEY_COLOR_SPECULAR) != AI_SUCCESS && mat.Get(AI_MATKEY_SPECULAR_FACTOR, specular.specularFactor) != AI_SUCCESS) {
+        return false;
+    }
+
+    // default factors of zero disables specular, so do not export
+    if (specular.specularFactor == 0.0f && (specular.specularColorFactor[0] == defaultSpecularColorFactor[0] && specular.specularColorFactor[1] == defaultSpecularColorFactor[1] && specular.specularColorFactor[2] == defaultSpecularColorFactor[2])) {
+        return false;
+    }
+
+    // Add any appropriate textures
+    GetMatTex(mat, specular.specularTexture, aiTextureType_SPECULAR);
+    GetMatTex(mat, specular.specularColorTexture, aiTextureType_SPECULAR);
+
+    return true;
+}
+
 bool glTF2Exporter::GetMatSheen(const aiMaterial &mat, glTF2::MaterialSheen &sheen) {
     // Return true if got any valid Sheen properties or textures
     if (GetMatColor(mat, sheen.sheenColorFactor, AI_MATKEY_SHEEN_COLOR_FACTOR) != aiReturn_SUCCESS) {
@@ -816,7 +837,7 @@ void glTF2Exporter::ExportMaterials() {
 
         {
             // KHR_materials_pbrSpecularGlossiness extension
-            // NOTE: This extension is being considered for deprecation (Dec 2020)
+            // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
             PbrSpecularGlossiness pbrSG;
             if (GetMatSpecGloss(mat, pbrSG)) {
                 mAsset->extensionsUsed.KHR_materials_pbrSpecularGlossiness = true;
@@ -833,7 +854,12 @@ void glTF2Exporter::ExportMaterials() {
         } else {
             // These extensions are not compatible with KHR_materials_unlit or KHR_materials_pbrSpecularGlossiness
             if (!m->pbrSpecularGlossiness.isPresent) {
-                // Sheen
+                MaterialSpecular specular;
+                if (GetMatSpecular(mat, specular)) {
+                    mAsset->extensionsUsed.KHR_materials_specular = true;
+                    m->materialSpecular = Nullable<MaterialSpecular>(specular);
+                }
+
                 MaterialSheen sheen;
                 if (GetMatSheen(mat, sheen)) {
                     mAsset->extensionsUsed.KHR_materials_sheen = true;
diff --git a/code/AssetLib/glTF2/glTF2Exporter.h b/code/AssetLib/glTF2/glTF2Exporter.h
index 99425228e..f211d2d53 100644
--- a/code/AssetLib/glTF2/glTF2Exporter.h
+++ b/code/AssetLib/glTF2/glTF2Exporter.h
@@ -76,6 +76,7 @@ struct OcclusionTextureInfo;
 struct Node;
 struct Texture;
 struct PbrSpecularGlossiness;
+struct MaterialSpecular;
 struct MaterialSheen;
 struct MaterialClearcoat;
 struct MaterialTransmission;
@@ -116,6 +117,7 @@ protected:
     aiReturn GetMatColor(const aiMaterial &mat, glTF2::vec4 &prop, const char *propName, int type, int idx) const;
     aiReturn GetMatColor(const aiMaterial &mat, glTF2::vec3 &prop, const char *propName, int type, int idx) const;
     bool GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlossiness &pbrSG);
+    bool GetMatSpecular(const aiMaterial &mat, glTF2::MaterialSpecular &specular);
     bool GetMatSheen(const aiMaterial &mat, glTF2::MaterialSheen &sheen);
     bool GetMatClearcoat(const aiMaterial &mat, glTF2::MaterialClearcoat &clearcoat);
     bool GetMatTransmission(const aiMaterial &mat, glTF2::MaterialTransmission &transmission);
diff --git a/code/AssetLib/glTF2/glTF2Importer.cpp b/code/AssetLib/glTF2/glTF2Importer.cpp
index 947edc8d5..1757026fe 100644
--- a/code/AssetLib/glTF2/glTF2Importer.cpp
+++ b/code/AssetLib/glTF2/glTF2Importer.cpp
@@ -283,8 +283,9 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
         aimat->AddProperty(&mat.alphaCutoff, 1, AI_MATKEY_GLTF_ALPHACUTOFF);
 
         // pbrSpecularGlossiness
-        if (mat.pbrSpecularGlossiness.isPresent) {
+        if (mat.pbrSpecularGlossiness.isPresent) { // TODO: Consider importing this only if KHR_materials_specular isn't also defined
             PbrSpecularGlossiness &pbrSG = mat.pbrSpecularGlossiness.value;
+            aimat->AddProperty(new int(1), 1, AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS);
 
             SetMaterialColorProperty(r, pbrSG.diffuseFactor, aimat, AI_MATKEY_COLOR_DIFFUSE);
             SetMaterialColorProperty(r, pbrSG.specularFactor, aimat, AI_MATKEY_COLOR_SPECULAR);
@@ -307,6 +308,18 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
 
         aimat->AddProperty(&shadingMode, 1, AI_MATKEY_SHADING_MODEL);
 
+        // KHR_materials_specular
+        if (mat.materialSpecular.isPresent) {
+            MaterialSpecular &specular = mat.materialSpecular.value;
+            // Default values of zero disables Specular
+            if (std::memcmp(specular.specularColorFactor, defaultSpecularColorFactor, sizeof(glTFCommon::vec3)) != 0 || specular.specularFactor != 0.0f) {
+                SetMaterialColorProperty(r, specular.specularColorFactor, aimat, AI_MATKEY_COLOR_SPECULAR);
+                aimat->AddProperty(&specular.specularFactor, 1, AI_MATKEY_SPECULAR_FACTOR);
+                SetMaterialTextureProperty(embeddedTexIdxs, r, specular.specularTexture, aimat, aiTextureType_SPECULAR);
+                SetMaterialTextureProperty(embeddedTexIdxs, r, specular.specularColorTexture, aimat, aiTextureType_SPECULAR);
+            }
+        }
+
         // KHR_materials_sheen
         if (mat.materialSheen.isPresent) {
             MaterialSheen &sheen = mat.materialSheen.value;
diff --git a/include/assimp/material.h b/include/assimp/material.h
index 0052888d1..92f7ab8ca 100644
--- a/include/assimp/material.h
+++ b/include/assimp/material.h
@@ -1000,6 +1000,7 @@ extern "C" {
 // Specular Color.
 // Note: Metallic/Roughness may also have a Specular Color
 // AI_MATKEY_COLOR_SPECULAR
+#define AI_MATKEY_USE_PBR_SPECULAR_GLOSSINESS "$mat.useGltfPbrSpecularGlossiness", 0, 0
 #define AI_MATKEY_SPECULAR_FACTOR "$mat.specularFactor", 0, 0
 // Glossiness factor. 0.0 = Completely Rough, 1.0 = Perfectly Smooth
 #define AI_MATKEY_GLOSSINESS_FACTOR "$mat.glossinessFactor", 0, 0

From ffaf378ee6107221c3a731039d3872910801137f Mon Sep 17 00:00:00 2001
From: Adam <adam.v.beili@gmail.com>
Date: Thu, 10 Nov 2022 20:37:46 +0200
Subject: [PATCH 2/9] fixed misnamed matkey

---
 include/assimp/material.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/assimp/material.h b/include/assimp/material.h
index 92f7ab8ca..3a623d10e 100644
--- a/include/assimp/material.h
+++ b/include/assimp/material.h
@@ -1000,7 +1000,7 @@ extern "C" {
 // Specular Color.
 // Note: Metallic/Roughness may also have a Specular Color
 // AI_MATKEY_COLOR_SPECULAR
-#define AI_MATKEY_USE_PBR_SPECULAR_GLOSSINESS "$mat.useGltfPbrSpecularGlossiness", 0, 0
+#define AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS "$mat.useGltfPbrSpecularGlossiness", 0, 0
 #define AI_MATKEY_SPECULAR_FACTOR "$mat.specularFactor", 0, 0
 // Glossiness factor. 0.0 = Completely Rough, 1.0 = Perfectly Smooth
 #define AI_MATKEY_GLOSSINESS_FACTOR "$mat.glossinessFactor", 0, 0

From 1cd5841b2f331ba630d7a873a4e59dbf3449d711 Mon Sep 17 00:00:00 2001
From: Adam <adam.v.beili@gmail.com>
Date: Fri, 18 Nov 2022 17:24:37 +0200
Subject: [PATCH 3/9] .

---
 code/AssetLib/glTF2/glTF2AssetWriter.inl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.inl b/code/AssetLib/glTF2/glTF2AssetWriter.inl
index c57603bb0..de1e25fc1 100644
--- a/code/AssetLib/glTF2/glTF2AssetWriter.inl
+++ b/code/AssetLib/glTF2/glTF2AssetWriter.inl
@@ -435,6 +435,7 @@ namespace glTF2 {
 
             if (!materialSpecular.ObjectEmpty()) {
                 exts.AddMember("KHR_materials_specular", materialSpecular, w.mAl);
+            }
         }
 
         if (m.materialSheen.isPresent) {

From fa00571049b601d970ebc61331fc9fbb66e217ce Mon Sep 17 00:00:00 2001
From: Adam Beili <54665621+Beilinson@users.noreply.github.com>
Date: Sun, 26 Mar 2023 14:52:44 +0200
Subject: [PATCH 4/9] fixed compilation bug

---
 code/AssetLib/glTF2/glTF2Exporter.cpp | 35 ++++++++++++---------------
 code/AssetLib/glTF2/glTF2Importer.cpp | 25 +++++++++----------
 2 files changed, 28 insertions(+), 32 deletions(-)

diff --git a/code/AssetLib/glTF2/glTF2Exporter.cpp b/code/AssetLib/glTF2/glTF2Exporter.cpp
index 464a045b9..17140aa6a 100644
--- a/code/AssetLib/glTF2/glTF2Exporter.cpp
+++ b/code/AssetLib/glTF2/glTF2Exporter.cpp
@@ -640,14 +640,16 @@ aiReturn glTF2Exporter::GetMatColor(const aiMaterial &mat, vec3 &prop, const cha
     return result;
 }
 
+// This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
 bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlossiness &pbrSG) {
-    bool result = false;
-    // If has Glossiness, a Specular Color or Specular Texture, use the KHR_materials_pbrSpecularGlossiness extension
-    // NOTE: This extension is being considered for deprecation (Dec 2020), may be replaced by KHR_material_specular
-    // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
-    if (mat.Get(AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS) != AI_SUCCESS) {
+    int usePbrSpecGloss;
+    if (mat.Get(AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS, usePbrSpecGloss) != AI_SUCCESS) {
         return false;
     }
+    
+    bool result = false;
+    
+    // If has Glossiness, a Specular Color or Specular Texture, use the KHR_materials_pbrSpecularGlossiness extension
     if (mat.Get(AI_MATKEY_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) == AI_SUCCESS) {
         result = true;
     } else {
@@ -678,21 +680,16 @@ bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlo
 }
 
 bool glTF2Exporter::GetMatSpecular(const aiMaterial &mat, glTF2::MaterialSpecular &specular) {
-    // Specular requires either/or
-    if (GetMatColor(mat, specular.specularColorFactor, AI_MATKEY_COLOR_SPECULAR) != AI_SUCCESS && mat.Get(AI_MATKEY_SPECULAR_FACTOR, specular.specularFactor) != AI_SUCCESS) {
-        return false;
+    // Specular requires either/or, default factors of zero disables specular, so do not export
+    bool result = false;
+    if (GetMatColor(mat, specular.specularColorFactor, AI_MATKEY_COLOR_SPECULAR) == AI_SUCCESS && specular.specularFactor != 0.0f) {
+        GetMatTex(mat, specular.specularColorTexture, aiTextureType_SPECULAR);
+        result = true;
+    } else if (mat.Get(AI_MATKEY_SPECULAR_FACTOR, specular.specularFactor) == AI_SUCCESS && !(specular.specularColorFactor[0] == defaultSpecularColorFactor[0] && specular.specularColorFactor[1] == defaultSpecularColorFactor[1] && specular.specularColorFactor[2] == defaultSpecularColorFactor[2])) {
+        GetMatTex(mat, specular.specularTexture, aiTextureType_SPECULAR);
+        result = true;
     }
-
-    // default factors of zero disables specular, so do not export
-    if (specular.specularFactor == 0.0f && (specular.specularColorFactor[0] == defaultSpecularColorFactor[0] && specular.specularColorFactor[1] == defaultSpecularColorFactor[1] && specular.specularColorFactor[2] == defaultSpecularColorFactor[2])) {
-        return false;
-    }
-
-    // Add any appropriate textures
-    GetMatTex(mat, specular.specularTexture, aiTextureType_SPECULAR);
-    GetMatTex(mat, specular.specularColorTexture, aiTextureType_SPECULAR);
-
-    return true;
+    return result;
 }
 
 bool glTF2Exporter::GetMatSheen(const aiMaterial &mat, glTF2::MaterialSheen &sheen) {
diff --git a/code/AssetLib/glTF2/glTF2Importer.cpp b/code/AssetLib/glTF2/glTF2Importer.cpp
index 805ae0548..f298e7037 100644
--- a/code/AssetLib/glTF2/glTF2Importer.cpp
+++ b/code/AssetLib/glTF2/glTF2Importer.cpp
@@ -278,8 +278,19 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
         aimat->AddProperty(&alphaMode, AI_MATKEY_GLTF_ALPHAMODE);
         aimat->AddProperty(&mat.alphaCutoff, 1, AI_MATKEY_GLTF_ALPHACUTOFF);
 
+        // KHR_materials_specular
+        if (mat.materialSpecular.isPresent) {
+            MaterialSpecular &specular = mat.materialSpecular.value;
+            // Default values of zero disables Specular
+            if (std::memcmp(specular.specularColorFactor, defaultSpecularColorFactor, sizeof(glTFCommon::vec3)) != 0 || specular.specularFactor != 0.0f) {
+                SetMaterialColorProperty(r, specular.specularColorFactor, aimat, AI_MATKEY_COLOR_SPECULAR);
+                aimat->AddProperty(&specular.specularFactor, 1, AI_MATKEY_SPECULAR_FACTOR);
+                SetMaterialTextureProperty(embeddedTexIdxs, r, specular.specularTexture, aimat, aiTextureType_SPECULAR);
+                SetMaterialTextureProperty(embeddedTexIdxs, r, specular.specularColorTexture, aimat, aiTextureType_SPECULAR);
+            }
+        }
         // pbrSpecularGlossiness
-        if (mat.pbrSpecularGlossiness.isPresent) { // TODO: Consider importing this only if KHR_materials_specular isn't also defined
+        else if (mat.pbrSpecularGlossiness.isPresent) {
             PbrSpecularGlossiness &pbrSG = mat.pbrSpecularGlossiness.value;
             aimat->AddProperty(new int(1), 1, AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS);
 
@@ -304,18 +315,6 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
 
         aimat->AddProperty(&shadingMode, 1, AI_MATKEY_SHADING_MODEL);
 
-        // KHR_materials_specular
-        if (mat.materialSpecular.isPresent) {
-            MaterialSpecular &specular = mat.materialSpecular.value;
-            // Default values of zero disables Specular
-            if (std::memcmp(specular.specularColorFactor, defaultSpecularColorFactor, sizeof(glTFCommon::vec3)) != 0 || specular.specularFactor != 0.0f) {
-                SetMaterialColorProperty(r, specular.specularColorFactor, aimat, AI_MATKEY_COLOR_SPECULAR);
-                aimat->AddProperty(&specular.specularFactor, 1, AI_MATKEY_SPECULAR_FACTOR);
-                SetMaterialTextureProperty(embeddedTexIdxs, r, specular.specularTexture, aimat, aiTextureType_SPECULAR);
-                SetMaterialTextureProperty(embeddedTexIdxs, r, specular.specularColorTexture, aimat, aiTextureType_SPECULAR);
-            }
-        }
-
         // KHR_materials_sheen
         if (mat.materialSheen.isPresent) {
             MaterialSheen &sheen = mat.materialSheen.value;

From 83053f3d564a0ba624c0165364403e8b2e6bcba3 Mon Sep 17 00:00:00 2001
From: Adam Beili <54665621+Beilinson@users.noreply.github.com>
Date: Sun, 26 Mar 2023 16:55:38 +0200
Subject: [PATCH 5/9] Made usePbrSpecGloss a exportproperty, fixed mat_specular
 to spec

---
 code/AssetLib/glTF2/glTF2Exporter.cpp | 34 +++++++++++++--------------
 code/AssetLib/glTF2/glTF2Importer.cpp |  1 -
 include/assimp/config.h.in            | 11 +++++++++
 include/assimp/material.h             |  1 -
 test/unit/utglTF2ImportExport.cpp     |  4 +++-
 5 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/code/AssetLib/glTF2/glTF2Exporter.cpp b/code/AssetLib/glTF2/glTF2Exporter.cpp
index 17140aa6a..3a1441ad9 100644
--- a/code/AssetLib/glTF2/glTF2Exporter.cpp
+++ b/code/AssetLib/glTF2/glTF2Exporter.cpp
@@ -642,13 +642,7 @@ aiReturn glTF2Exporter::GetMatColor(const aiMaterial &mat, vec3 &prop, const cha
 
 // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
 bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlossiness &pbrSG) {
-    int usePbrSpecGloss;
-    if (mat.Get(AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS, usePbrSpecGloss) != AI_SUCCESS) {
-        return false;
-    }
-    
     bool result = false;
-    
     // If has Glossiness, a Specular Color or Specular Texture, use the KHR_materials_pbrSpecularGlossiness extension
     if (mat.Get(AI_MATKEY_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) == AI_SUCCESS) {
         result = true;
@@ -681,15 +675,21 @@ bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlo
 
 bool glTF2Exporter::GetMatSpecular(const aiMaterial &mat, glTF2::MaterialSpecular &specular) {
     // Specular requires either/or, default factors of zero disables specular, so do not export
-    bool result = false;
-    if (GetMatColor(mat, specular.specularColorFactor, AI_MATKEY_COLOR_SPECULAR) == AI_SUCCESS && specular.specularFactor != 0.0f) {
-        GetMatTex(mat, specular.specularColorTexture, aiTextureType_SPECULAR);
-        result = true;
-    } else if (mat.Get(AI_MATKEY_SPECULAR_FACTOR, specular.specularFactor) == AI_SUCCESS && !(specular.specularColorFactor[0] == defaultSpecularColorFactor[0] && specular.specularColorFactor[1] == defaultSpecularColorFactor[1] && specular.specularColorFactor[2] == defaultSpecularColorFactor[2])) {
-        GetMatTex(mat, specular.specularTexture, aiTextureType_SPECULAR);
-        result = true;
+    if (GetMatColor(mat, specular.specularColorFactor, AI_MATKEY_COLOR_SPECULAR) != AI_SUCCESS || mat.Get(AI_MATKEY_SPECULAR_FACTOR, specular.specularFactor) != AI_SUCCESS) {
+        return false;
     }
-    return result;
+    // The spec states that the default is 1.0 and [1.0, 1.0, 1.0]. We if both are 0, which should disable specular. Otherwise, if one is 0, set to 1.0
+    const bool colorFactorIsZero = specular.specularColorFactor[0] == defaultSpecularColorFactor[0] && specular.specularColorFactor[1] == defaultSpecularColorFactor[1] && specular.specularColorFactor[2] == defaultSpecularColorFactor[2];
+    if (specular.specularFactor == 0.0f && colorFactorIsZero) {
+        return false;
+    } else if (specular.specularFactor == 0.0f) {
+        specular.specularFactor = 1.0f;
+    } else if (colorFactorIsZero) {
+        specular.specularColorFactor[0] = specular.specularColorFactor[1] = specular.specularColorFactor[2] = 1.0f;
+    }
+    GetMatTex(mat, specular.specularColorTexture, aiTextureType_SPECULAR);
+    GetMatTex(mat, specular.specularTexture, aiTextureType_SPECULAR);
+    return true;
 }
 
 bool glTF2Exporter::GetMatSheen(const aiMaterial &mat, glTF2::MaterialSheen &sheen) {
@@ -755,7 +755,7 @@ bool glTF2Exporter::GetMatEmissiveStrength(const aiMaterial &mat, glTF2::Materia
     return mat.Get(AI_MATKEY_EMISSIVE_INTENSITY, emissiveStrength.emissiveStrength) == aiReturn_SUCCESS;
 }
 
-void glTF2Exporter::ExportMaterials() {
+void glTF2Exporter::ExportMaterials(ExportProperties *pProperties) {
     aiString aiName;
     for (unsigned int i = 0; i < mScene->mNumMaterials; ++i) {
         ai_assert(mScene->mMaterials[i] != nullptr);
@@ -836,9 +836,9 @@ void glTF2Exporter::ExportMaterials() {
             m->alphaMode = alphaMode.C_Str();
         }
 
-        {
+        // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
+        if (pProperties->GetPropertyBool(AI_CONFIG_USE_GLTF_PBR_SPECULAR_GLOSSINESS)) {
             // KHR_materials_pbrSpecularGlossiness extension
-            // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
             PbrSpecularGlossiness pbrSG;
             if (GetMatSpecGloss(mat, pbrSG)) {
                 mAsset->extensionsUsed.KHR_materials_pbrSpecularGlossiness = true;
diff --git a/code/AssetLib/glTF2/glTF2Importer.cpp b/code/AssetLib/glTF2/glTF2Importer.cpp
index f298e7037..4a3ee4928 100644
--- a/code/AssetLib/glTF2/glTF2Importer.cpp
+++ b/code/AssetLib/glTF2/glTF2Importer.cpp
@@ -292,7 +292,6 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
         // pbrSpecularGlossiness
         else if (mat.pbrSpecularGlossiness.isPresent) {
             PbrSpecularGlossiness &pbrSG = mat.pbrSpecularGlossiness.value;
-            aimat->AddProperty(new int(1), 1, AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS);
 
             SetMaterialColorProperty(r, pbrSG.diffuseFactor, aimat, AI_MATKEY_COLOR_DIFFUSE);
             SetMaterialColorProperty(r, pbrSG.specularFactor, aimat, AI_MATKEY_COLOR_SPECULAR);
diff --git a/include/assimp/config.h.in b/include/assimp/config.h.in
index ad16fa88c..9e843a20d 100644
--- a/include/assimp/config.h.in
+++ b/include/assimp/config.h.in
@@ -1065,6 +1065,17 @@ enum aiComponent
  */
 #define AI_CONFIG_EXPORT_POINT_CLOUDS "EXPORT_POINT_CLOUDS"
 
+/** @brief Specifies whether to use the deprecated KHR_materials_pbrSpecularGlossiness extension
+ * 
+ * When this flag is undefined any material with specularity will use the new KHR_materials_specular
+ * extension. Enabling this flag will revert to the deprecated extension. Note that exporting
+ * KHR_materials_pbrSpecularGlossiness with extensions other than KHR_materials_unlit is unsupported,
+ * including the basic pbrMetallicRoughness spec.
+ *
+ * Property type: Bool. Default value: false.
+ */
+#define AI_CONFIG_USE_GLTF_PBR_SPECULAR_GLOSSINESS "USE_GLTF_PBR_SPECULAR_GLOSSINESS"
+
 /**
  * @brief Specifies the blob name, assimp uses for exporting.
  * 
diff --git a/include/assimp/material.h b/include/assimp/material.h
index f583ad8a8..80551e53d 100644
--- a/include/assimp/material.h
+++ b/include/assimp/material.h
@@ -1000,7 +1000,6 @@ extern "C" {
 // Specular Color.
 // Note: Metallic/Roughness may also have a Specular Color
 // AI_MATKEY_COLOR_SPECULAR
-#define AI_MATKEY_USE_GLTF_PBR_SPECULAR_GLOSSINESS "$mat.useGltfPbrSpecularGlossiness", 0, 0
 #define AI_MATKEY_SPECULAR_FACTOR "$mat.specularFactor", 0, 0
 // Glossiness factor. 0.0 = Completely Rough, 1.0 = Perfectly Smooth
 #define AI_MATKEY_GLOSSINESS_FACTOR "$mat.glossinessFactor", 0, 0
diff --git a/test/unit/utglTF2ImportExport.cpp b/test/unit/utglTF2ImportExport.cpp
index ef3fc4137..c7d01fbcb 100644
--- a/test/unit/utglTF2ImportExport.cpp
+++ b/test/unit/utglTF2ImportExport.cpp
@@ -220,7 +220,9 @@ TEST_F(utglTF2ImportExport, importglTF2AndExport_KHR_materials_pbrSpecularGlossi
             aiProcess_ValidateDataStructure);
     EXPECT_NE(nullptr, scene);
     // Export
-    EXPECT_EQ(aiReturn_SUCCESS, exporter.Export(scene, "glb2", ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured_out.glb"));
+    ExportProperties props;
+    props.SetPropertyBool(, true);
+    EXPECT_EQ(aiReturn_SUCCESS, exporter.Export(scene, "glb2", ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured_out.glb", 0, &props));
 
     // And re-import
     EXPECT_TRUE(importerMatTest(ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured_out.glb", true));

From b6ecba9114e4bfa5edcf93b9f7ceea5c73b4fd9b Mon Sep 17 00:00:00 2001
From: Adam Beili <54665621+Beilinson@users.noreply.github.com>
Date: Sun, 26 Mar 2023 17:03:46 +0200
Subject: [PATCH 6/9] fix

---
 code/AssetLib/glTF2/glTF2Exporter.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/code/AssetLib/glTF2/glTF2Exporter.cpp b/code/AssetLib/glTF2/glTF2Exporter.cpp
index 3a1441ad9..777df50fd 100644
--- a/code/AssetLib/glTF2/glTF2Exporter.cpp
+++ b/code/AssetLib/glTF2/glTF2Exporter.cpp
@@ -755,7 +755,7 @@ bool glTF2Exporter::GetMatEmissiveStrength(const aiMaterial &mat, glTF2::Materia
     return mat.Get(AI_MATKEY_EMISSIVE_INTENSITY, emissiveStrength.emissiveStrength) == aiReturn_SUCCESS;
 }
 
-void glTF2Exporter::ExportMaterials(ExportProperties *pProperties) {
+void glTF2Exporter::ExportMaterials() {
     aiString aiName;
     for (unsigned int i = 0; i < mScene->mNumMaterials; ++i) {
         ai_assert(mScene->mMaterials[i] != nullptr);
@@ -837,7 +837,7 @@ void glTF2Exporter::ExportMaterials(ExportProperties *pProperties) {
         }
 
         // This extension has been deprecated, only export with the specific flag enabled, defaults to false. Uses KHR_material_specular default.
-        if (pProperties->GetPropertyBool(AI_CONFIG_USE_GLTF_PBR_SPECULAR_GLOSSINESS)) {
+        if (mProperties->GetPropertyBool(AI_CONFIG_USE_GLTF_PBR_SPECULAR_GLOSSINESS)) {
             // KHR_materials_pbrSpecularGlossiness extension
             PbrSpecularGlossiness pbrSG;
             if (GetMatSpecGloss(mat, pbrSG)) {

From 8ac0af5c58788e48412dc19fca49808fdd357c3f Mon Sep 17 00:00:00 2001
From: Adam Beili <54665621+Beilinson@users.noreply.github.com>
Date: Sun, 26 Mar 2023 17:13:16 +0200
Subject: [PATCH 7/9] .

---
 code/AssetLib/glTF2/glTF2Asset.inl       | 2 +-
 code/AssetLib/glTF2/glTF2AssetWriter.inl | 2 +-
 test/unit/utglTF2ImportExport.cpp        | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/code/AssetLib/glTF2/glTF2Asset.inl b/code/AssetLib/glTF2/glTF2Asset.inl
index db773513b..3a3ba376e 100644
--- a/code/AssetLib/glTF2/glTF2Asset.inl
+++ b/code/AssetLib/glTF2/glTF2Asset.inl
@@ -1236,7 +1236,7 @@ inline void Material::Read(Value &material, Asset &r) {
     ReadMember(material, "alphaCutoff", this->alphaCutoff);
 
     if (Value *extensions = FindObject(material, "extensions")) {
-        if (r.extensionsUsed.KHR_materials_pbrSpecularGlossiness) {  //TODO: Maybe ignore this if KHR_materials_specular is also defined
+        if (r.extensionsUsed.KHR_materials_pbrSpecularGlossiness) { 
             if (Value *curPbrSpecularGlossiness = FindObject(*extensions, "KHR_materials_pbrSpecularGlossiness")) {
                 PbrSpecularGlossiness pbrSG;
 
diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.inl b/code/AssetLib/glTF2/glTF2AssetWriter.inl
index ef1c66b3b..f6fc7adff 100644
--- a/code/AssetLib/glTF2/glTF2AssetWriter.inl
+++ b/code/AssetLib/glTF2/glTF2AssetWriter.inl
@@ -424,7 +424,7 @@ namespace glTF2 {
 
             MaterialSpecular &specular = m.materialSpecular.value;
 
-            if (specular.specularFactor != 0.f) {
+            if (specular.specularFactor != 0.0f) {
                 WriteFloat(materialSpecular, specular.specularFactor, "specularFactor", w.mAl);
                 WriteTex(materialSpecular, specular.specularTexture, "specularTexture", w.mAl);
             }
diff --git a/test/unit/utglTF2ImportExport.cpp b/test/unit/utglTF2ImportExport.cpp
index c7d01fbcb..b63fd3944 100644
--- a/test/unit/utglTF2ImportExport.cpp
+++ b/test/unit/utglTF2ImportExport.cpp
@@ -221,7 +221,7 @@ TEST_F(utglTF2ImportExport, importglTF2AndExport_KHR_materials_pbrSpecularGlossi
     EXPECT_NE(nullptr, scene);
     // Export
     ExportProperties props;
-    props.SetPropertyBool(, true);
+    props.SetPropertyBool(AI_CONFIG_USE_GLTF_PBR_SPECULAR_GLOSSINESS, true);
     EXPECT_EQ(aiReturn_SUCCESS, exporter.Export(scene, "glb2", ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured_out.glb", 0, &props));
 
     // And re-import

From 3a09fd0c859cafea48dd272ac3a66bced00b5ee8 Mon Sep 17 00:00:00 2001
From: Kim Kulling <kimkulling@users.noreply.github.com>
Date: Tue, 23 May 2023 09:50:20 +0200
Subject: [PATCH 8/9] Fix review finding

Test with glossiness disabled and enabled.
---
 test/unit/utglTF2ImportExport.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/test/unit/utglTF2ImportExport.cpp b/test/unit/utglTF2ImportExport.cpp
index 56f79d307..91ac87ee5 100644
--- a/test/unit/utglTF2ImportExport.cpp
+++ b/test/unit/utglTF2ImportExport.cpp
@@ -219,7 +219,11 @@ TEST_F(utglTF2ImportExport, importglTF2AndExport_KHR_materials_pbrSpecularGlossi
     const aiScene *scene = importer.ReadFile(ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured.gltf",
             aiProcess_ValidateDataStructure);
     EXPECT_NE(nullptr, scene);
-    // Export
+    
+    // Export with specular glossiness disabled
+    EXPECT_EQ(aiReturn_SUCCESS, exporter.Export(scene, "glb2", ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured_out.glb"));
+    
+    // Export with specular glossiness enabled
     ExportProperties props;
     props.SetPropertyBool(AI_CONFIG_USE_GLTF_PBR_SPECULAR_GLOSSINESS, true);
     EXPECT_EQ(aiReturn_SUCCESS, exporter.Export(scene, "glb2", ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured_out.glb", 0, &props));

From b7a8c4ba75501554cec5069ad67c6fe6508db714 Mon Sep 17 00:00:00 2001
From: Kim Kulling <kimkulling@users.noreply.github.com>
Date: Tue, 23 May 2023 10:33:14 +0200
Subject: [PATCH 9/9] Update glTF2Asset.inl

---
 code/AssetLib/glTF2/glTF2Asset.inl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/code/AssetLib/glTF2/glTF2Asset.inl b/code/AssetLib/glTF2/glTF2Asset.inl
index da5ef182b..bd6435766 100644
--- a/code/AssetLib/glTF2/glTF2Asset.inl
+++ b/code/AssetLib/glTF2/glTF2Asset.inl
@@ -1250,7 +1250,7 @@ inline void Material::Read(Value &material, Asset &r) {
     ReadMember(material, "alphaCutoff", this->alphaCutoff);
 
     if (Value *extensions = FindObject(material, "extensions")) {
-        if (r.extensionsUsed.KHR_materials_pbrSpecularGlossiness) { 
+        if (r.extensionsUsed.KHR_materials_pbrSpecularGlossiness) {
             if (Value *curPbrSpecularGlossiness = FindObject(*extensions, "KHR_materials_pbrSpecularGlossiness")) {
                 PbrSpecularGlossiness pbrSG;