glTF 2.0: Import scale for normal textures and strength for occlusion textures

resolves #1693

code/glTF2Asset.h

@@ -181,13 +181,17 @@ namespace glTF2
 	#define _AI_MATKEY_GLTF_MAPPINGID_BASE "$tex.mappingid"
 	#define _AI_MATKEY_GLTF_MAPPINGFILTER_MAG_BASE "$tex.mappingfiltermag"
 	#define _AI_MATKEY_GLTF_MAPPINGFILTER_MIN_BASE "$tex.mappingfiltermin"
+    #define _AI_MATKEY_GLTF_SCALE_BASE "$tex.scale"
+    #define _AI_MATKEY_GLTF_STRENGTH_BASE "$tex.strength"
 
 	#define AI_MATKEY_GLTF_TEXTURE_TEXCOORD _AI_MATKEY_GLTF_TEXTURE_TEXCOORD_BASE, type, N
 	#define AI_MATKEY_GLTF_MAPPINGNAME(type, N) _AI_MATKEY_GLTF_MAPPINGNAME_BASE, type, N
 	#define AI_MATKEY_GLTF_MAPPINGID(type, N) _AI_MATKEY_GLTF_MAPPINGID_BASE, type, N
 	#define AI_MATKEY_GLTF_MAPPINGFILTER_MAG(type, N) _AI_MATKEY_GLTF_MAPPINGFILTER_MAG_BASE, type, N
 	#define AI_MATKEY_GLTF_MAPPINGFILTER_MIN(type, N) _AI_MATKEY_GLTF_MAPPINGFILTER_MIN_BASE, type, N
-
+    #define AI_MATKEY_GLTF_TEXTURE_SCALE(type, N) _AI_MATKEY_GLTF_SCALE_BASE, type, N
+    #define AI_MATKEY_GLTF_TEXTURE_STRENGTH(type, N) _AI_MATKEY_GLTF_STRENGTH_BASE, type, N
+    
     #ifdef ASSIMP_API
         #include "./../include/assimp/Compiler/pushpack1.h"
     #endif

code/glTF2Importer.cpp

@@ -211,6 +211,24 @@ inline void SetMaterialTextureProperty(std::vector<int>& embeddedTexIdxs, Asset&
     }
 }
 
+inline void SetMaterialTextureProperty(std::vector<int>& embeddedTexIdxs, Asset& r, glTF2::NormalTextureInfo& prop, aiMaterial* mat, aiTextureType texType, unsigned int texSlot = 0)
+{
+    SetMaterialTextureProperty( embeddedTexIdxs, r, (glTF2::TextureInfo) prop, mat, texType, texSlot );
+
+    if (prop.texture && prop.texture->source) {
+         mat->AddProperty(&prop.scale, 1, AI_MATKEY_GLTF_TEXTURE_SCALE(texType, texSlot));
+    }
+}
+
+inline void SetMaterialTextureProperty(std::vector<int>& embeddedTexIdxs, Asset& r, glTF2::OcclusionTextureInfo& prop, aiMaterial* mat, aiTextureType texType, unsigned int texSlot = 0)
+{
+    SetMaterialTextureProperty( embeddedTexIdxs, r, (glTF2::TextureInfo) prop, mat, texType, texSlot );
+
+    if (prop.texture && prop.texture->source) {
+        mat->AddProperty(&prop.strength, 1, AI_MATKEY_GLTF_TEXTURE_STRENGTH(texType, texSlot));
+    }
+}
+
 static aiMaterial* ImportMaterial(std::vector<int>& embeddedTexIdxs, Asset& r, Material& mat)
 {
     aiMaterial* aimat = new aiMaterial();