From 27025092c0ad7d7b3f500d4ae1dabb7570daf813 Mon Sep 17 00:00:00 2001
From: Mikulas Florek <mikulas.florek@gamedev.sk>
Date: Wed, 18 Dec 2024 11:40:15 +0100
Subject: [PATCH] fbx import - properly handle empty meshes

---
 external/openfbx/ofbx.cpp            | 17 ++++++++++++-----
 external/openfbx/ofbx.h              | 11 +++++++++--
 src/renderer/editor/fbx_importer.cpp |  2 ++
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/external/openfbx/ofbx.cpp b/external/openfbx/ofbx.cpp
index 83ba9e2afe..b2551b8b5f 100644
--- a/external/openfbx/ofbx.cpp
+++ b/external/openfbx/ofbx.cpp
@@ -1157,6 +1157,7 @@ struct GeometryPartitionImpl {
 };
 
 struct GeometryDataImpl : GeometryData {
+	bool has_vertices = false;
 	Vec3AttributesImpl positions;
 	Vec3AttributesImpl normals;
 	Vec3AttributesImpl tangents;
@@ -1176,6 +1177,8 @@ struct GeometryDataImpl : GeometryData {
 		return res;
 	}
 
+	bool hasVertices() const override { return has_vertices; }
+
 	Vec3Attributes getPositions() const override { return positions; }
 	Vec3Attributes getNormals() const override { return patchAttributes<Vec3Attributes>(normals); }
 	Vec2Attributes getUVs(int index) const override { return patchAttributes<Vec2Attributes>(uvs[index]); }
@@ -3126,16 +3129,22 @@ static OptionalError<Object*> parseAnimationCurve(const Scene& scene, const Elem
 	return curve;
 }
 
-static OptionalError<Object*> parseGeometry(const Element& element, GeometryImpl& geom, std::vector<ParseDataJob> &jobs, bool ignore_geometry, Allocator& allocator) {
+static OptionalError<Object*> parseGeometry(const Element& element, GeometryImpl& geom, std::vector<ParseDataJob> &jobs, u16 flags, Allocator& allocator) {
 	assert(element.first_property);
 
-	if (!parseGeometryMaterials(geom, element, jobs)) return Error("Invalid materials");
+	const bool ignore_geometry = (flags & (u16)LoadFlags::IGNORE_GEOMETRY) != 0;
+	const bool keep_matertial_map = (flags & (u16)LoadFlags::KEEP_MATERIAL_MAP) != 0;
+
+	if (keep_matertial_map || !ignore_geometry) {
+		if (!parseGeometryMaterials(geom, element, jobs)) return Error("Invalid materials");
+	}
 	
 	const Element* vertices_element = findChild(element, "Vertices");
 	if (!vertices_element || !vertices_element->first_property) {
 		return &geom;
 	}
 
+	geom.has_vertices = true;
 	const Element* polys_element = findChild(element, "PolygonVertexIndex");
 	if (!polys_element || !polys_element->first_property) return Error("Indices missing");
 
@@ -3451,9 +3460,7 @@ static bool parseObjects(const Element& root, Scene& scene, u16 flags, Allocator
 			if (last_prop && last_prop->value == "Mesh")
 			{
 				GeometryImpl* geom = allocator.allocate<GeometryImpl>(scene, *iter.second.element);
-				if (!ignore_geometry || keep_matertial_map) {
-					parseGeometry(*iter.second.element, *geom, jobs, ignore_geometry, allocator);
-				}
+				parseGeometry(*iter.second.element, *geom, jobs, flags, allocator);
 				obj = geom;
 				scene.m_geometries.push_back(geom);
 			}
diff --git a/external/openfbx/ofbx.h b/external/openfbx/ofbx.h
index 28154572c7..4717fc30af 100644
--- a/external/openfbx/ofbx.h
+++ b/external/openfbx/ofbx.h
@@ -536,6 +536,7 @@ struct GeometryPartition {
 	const int triangles_count; // number of triangles after polygon triangulation, can be used for preallocation
 };
 
+// if we use LoadFlags::IGNORE_GEOMETRY, values here are empty/invalid, with a few exceptions
 struct GeometryData {
 	virtual ~GeometryData() {}
 	
@@ -544,10 +545,16 @@ struct GeometryData {
 	virtual Vec2Attributes getUVs(int index = 0) const = 0;
 	virtual Vec4Attributes getColors() const = 0;
 	virtual Vec3Attributes getTangents() const = 0;
-	virtual const int getMaterialMapSize() const = 0;
-	virtual const int* getMaterialMap() const = 0;
 	virtual int getPartitionCount() const = 0;
 	virtual GeometryPartition getPartition(int partition_index) const = 0;
+	
+	// if we use LoadFlags::KEEP_MATERIAL_MAP, following is valid even if we use IGNORE_GEOMETRY
+	virtual const int getMaterialMapSize() const = 0;
+	virtual const int* getMaterialMap() const = 0;
+
+	// returns true if there are vertices in the geometry
+	// this has valid value even if we use LoadFlags::IGNORE_GEOMETRY
+	virtual bool hasVertices() const = 0;
 };
 
 
diff --git a/src/renderer/editor/fbx_importer.cpp b/src/renderer/editor/fbx_importer.cpp
index 60016ee84c..8b95b245a3 100644
--- a/src/renderer/editor/fbx_importer.cpp
+++ b/src/renderer/editor/fbx_importer.cpp
@@ -1114,6 +1114,8 @@ struct FBXImporter : ModelImporter {
 			// mark used materials/partitions
 			StackArray<bool, 16> used_materials(m_allocator);
 			used_materials.resize(mat_count);
+			if (!geom.hasVertices()) continue;
+
 			if (mat_count == 1) {
 				used_materials[0] = true;
 			}