From 7220104c37a40810ba725875e0fcc83e4d05cceb Mon Sep 17 00:00:00 2001
From: Josiah VanderZee <josiah_vanderzee@mediacombb.net>
Date: Sat, 12 Nov 2022 07:43:44 -0600
Subject: [PATCH] Test vertex normals on cube

---
 source/Irrlicht/CGLTFMeshFileLoader.cpp       | 23 ++++++++++++++++++-
 .../tests/testCGLTFMeshFileLoader.cpp         | 13 +++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/source/Irrlicht/CGLTFMeshFileLoader.cpp b/source/Irrlicht/CGLTFMeshFileLoader.cpp
index 3b533363..a1ef7b3f 100644
--- a/source/Irrlicht/CGLTFMeshFileLoader.cpp
+++ b/source/Irrlicht/CGLTFMeshFileLoader.cpp
@@ -87,7 +87,8 @@ static core::vector2df readVec2DF(const BufferOffset& readFrom)
 
 }
 
-static core::vector3df readVec3DF(const BufferOffset& readFrom, const float scale)
+static core::vector3df readVec3DF(const BufferOffset& readFrom,
+		const float scale = 1.0f)
 {
 	// glTF coordinates are right-handed, minetest ones are left-handed
 	// 1 glTF coordinate is equivalent to 10 Irrlicht coordinates
@@ -130,6 +131,20 @@ static void copyPositions(const tinygltf::Model& model,
 	}
 }
 
+static void copyNormals(const tinygltf::Model& model,
+		const Span<video::S3DVertex> vertices,
+		const std::size_t accessorId)
+{
+	const auto& view = model.bufferViews[
+		model.accessors[accessorId].bufferView];
+	const auto& buffer = model.buffers[view.buffer];
+	for (std::size_t i = 0; i < model.accessors[accessorId].count; ++i) {
+		const auto n = readVec3DF(BufferOffset(
+			buffer.data, view.byteOffset + 3 * sizeof(float) * i));
+		vertices.buffer[i].Normal = n;
+	}
+}
+
 static void copyTCoords(const tinygltf::Model& model,
 		const Span<video::S3DVertex> vertices,
 		const std::size_t accessorId)
@@ -153,6 +168,12 @@ static video::S3DVertex* getVertices(const tinygltf::Model& model,
 		vertexBuffer, model.accessors[accessorId].count};
 	copyPositions(model, vertices, accessorId);
 
+	const auto normalsField
+		= model.meshes[0].primitives[0].attributes.find("NORMAL");
+	if (normalsField != model.meshes[0].primitives[0].attributes.end()) {
+		copyNormals(model, vertices, normalsField->second);
+	}
+
 	const auto tCoordsField
 		= model.meshes[0].primitives[0].attributes.find("TEXCOORD_0");
 	if (tCoordsField != model.meshes[0].primitives[0].attributes.end()) {
diff --git a/source/Irrlicht/tests/testCGLTFMeshFileLoader.cpp b/source/Irrlicht/tests/testCGLTFMeshFileLoader.cpp
index a0a14052..74d10f0f 100644
--- a/source/Irrlicht/tests/testCGLTFMeshFileLoader.cpp
+++ b/source/Irrlicht/tests/testCGLTFMeshFileLoader.cpp
@@ -93,6 +93,19 @@ TEST_CASE("blender cube") {
 		CHECK(indices[2] == 9);
 	}
 
+	SECTION("vertex normals are correct") {
+		REQUIRE(sm.getMesh()->getMeshBuffer(0)->getVertexCount() == 24);
+		const auto* vertices = reinterpret_cast<irr::video::S3DVertex*>(
+			sm.getMesh()->getMeshBuffer(0)->getVertices());
+		CHECK(vertices[0].Normal == irr::core::vector3df{1.0f, 0.0f, 0.0f});
+		CHECK(vertices[1].Normal == irr::core::vector3df{0.0f, -1.0f, 0.0f});
+		CHECK(vertices[2].Normal == irr::core::vector3df{0.0f, 0.0f, 1.0f});
+		CHECK(vertices[3].Normal == irr::core::vector3df{1.0f, 0.0f, 0.0f});
+		CHECK(vertices[6].Normal == irr::core::vector3df{1.0f, 0.0f, 0.0f});
+		CHECK(vertices[23].Normal == irr::core::vector3df{-1.0f, 0.0f, 0.0f});
+
+	}
+
 	SECTION("texture coords are correct") {
 		REQUIRE(sm.getMesh()->getMeshBuffer(0)->getVertexCount() == 24);
 		const auto* vertices = reinterpret_cast<irr::video::S3DVertex*>(