From 036318e94e6b9f7d84daf5667368605ec034b28a Mon Sep 17 00:00:00 2001
From: Robert Beckebans <robert.beckebans@gmail.com>
Date: Wed, 4 Sep 2024 21:37:46 +0200
Subject: [PATCH] Fixed glTF normals when transforms have not been applied in
 Blender. close #929

---
 neo/idlib/MapFile_gltf.cpp | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/neo/idlib/MapFile_gltf.cpp b/neo/idlib/MapFile_gltf.cpp
index 1a99a951..442de586 100644
--- a/neo/idlib/MapFile_gltf.cpp
+++ b/neo/idlib/MapFile_gltf.cpp
@@ -153,14 +153,11 @@ MapPolygonMesh* MapPolygonMesh::ConvertFromMeshGltf( const gltfMesh_Primitive* p
 						bin.Seek( attrBv->byteStride - ( attrib->elementSize * attrAcc->typeSize ), FS_SEEK_CUR );
 					}
 
-					idVec3 normal;
-
-					normal.x = vec.x;
-					normal.y = vec.y;
-					normal.z = vec.z;
-
-					normal *= transform;
+					// w = 0 because we only want to rotate the normal
+					idVec4 normal4D( vec.x, vec.y, vec.z, 0.0f );
+					normal4D *= transform;
 
+					idVec3 normal = normal4D.ToVec3();
 					// renormalize because previous transforms may contain scale operations
 					normal.Normalize();
 
@@ -203,13 +200,10 @@ MapPolygonMesh* MapPolygonMesh::ConvertFromMeshGltf( const gltfMesh_Primitive* p
 						bin.Seek( attrBv->byteStride - ( attrib->elementSize * attrAcc->typeSize ), FS_SEEK_CUR );
 					}
 
-					idVec3 tangent;
+					idVec4 tangent4D( vec.x, vec.y, vec.z, 0.0f );
+					tangent4D *= transform;
 
-					tangent.x = vec.x;
-					tangent.y = vec.y;
-					tangent.z = vec.z;
-
-					tangent *= transform;
+					idVec3 tangent = tangent4D.ToVec3();
 					tangent.Normalize();
 
 					mesh->verts[i].SetTangent( tangent );