From 383c97e380517303ef4755a8ba6039e4dbabe0fd Mon Sep 17 00:00:00 2001
From: Danny Kabrane <danny.kabrane@4dpipeline.com>
Date: Wed, 23 Dec 2020 10:43:21 +0100
Subject: [PATCH] Add KHR_materials_transmission during export

---
 code/AssetLib/glTF2/glTF2AssetWriter.h   |  1 +
 code/AssetLib/glTF2/glTF2AssetWriter.inl | 20 ++++++++++++++++++++
 code/AssetLib/glTF2/glTF2Exporter.cpp    | 14 ++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.h b/code/AssetLib/glTF2/glTF2AssetWriter.h
index a31d79312..bf4f80dbe 100644
--- a/code/AssetLib/glTF2/glTF2AssetWriter.h
+++ b/code/AssetLib/glTF2/glTF2AssetWriter.h
@@ -48,6 +48,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *   KHR_materials_unlit: full
  *   KHR_materials_sheen: full
  *   KHR_materials_clearcoat: full
+ *   KHR_materials_transmission: full
  */
 #ifndef GLTF2ASSETWRITER_H_INC
 #define GLTF2ASSETWRITER_H_INC
diff --git a/code/AssetLib/glTF2/glTF2AssetWriter.inl b/code/AssetLib/glTF2/glTF2AssetWriter.inl
index 81ce1fd6e..65fddaec5 100644
--- a/code/AssetLib/glTF2/glTF2AssetWriter.inl
+++ b/code/AssetLib/glTF2/glTF2AssetWriter.inl
@@ -458,6 +458,22 @@ namespace glTF2 {
             }
         }
 
+        if (m.materialTransmission.isPresent) {
+            Value materialTransmission(rapidjson::Type::kObjectType);
+
+            MaterialTransmission &transmission = m.materialTransmission.value;
+
+            if (transmission.transmissionFactor != 0.f) {
+                WriteFloat(materialTransmission, transmission.transmissionFactor, "transmissionFactor", w.mAl);
+            }
+
+            WriteTex(materialTransmission, transmission.transmissionTexture, "transmissionTexture", w.mAl);
+                                   
+            if (!materialTransmission.ObjectEmpty()) {
+                exts.AddMember("KHR_materials_transmission", materialTransmission, w.mAl);
+            }
+        }
+
         if (!exts.ObjectEmpty()) {
             obj.AddMember("extensions", exts, w.mAl);
         }
@@ -857,6 +873,10 @@ namespace glTF2 {
             if (this->mAsset.extensionsUsed.KHR_materials_clearcoat) {
                 exts.PushBack(StringRef("KHR_materials_clearcoat"), mAl);
             }
+
+            if (this->mAsset.extensionsUsed.KHR_materials_transmission) {
+                exts.PushBack(StringRef("KHR_materials_transmission"), mAl);
+            }
         }
 
         if (!exts.Empty())
diff --git a/code/AssetLib/glTF2/glTF2Exporter.cpp b/code/AssetLib/glTF2/glTF2Exporter.cpp
index ba60be919..596ea6d28 100644
--- a/code/AssetLib/glTF2/glTF2Exporter.cpp
+++ b/code/AssetLib/glTF2/glTF2Exporter.cpp
@@ -747,6 +747,20 @@ void glTF2Exporter::ExportMaterials()
 
             m->materialClearcoat = Nullable<MaterialClearcoat>(clearcoat);
         }
+
+        bool hasMaterialTransmission = false;
+        mat->Get(AI_MATKEY_GLTF_MATERIAL_TRANSMISSION, hasMaterialTransmission);
+
+        if (hasMaterialTransmission) {
+            mAsset->extensionsUsed.KHR_materials_transmission = true;
+
+            MaterialTransmission transmission;
+
+            mat->Get(AI_MATKEY_GLTF_MATERIAL_TRANSMISSION_FACTOR, transmission.transmissionFactor);
+            GetMatTex(mat, transmission.transmissionTexture, AI_MATKEY_GLTF_MATERIAL_TRANSMISSION_TEXTURE);
+
+            m->materialTransmission = Nullable<MaterialTransmission>(transmission);
+        }
     }
 }