Adding mesh view scene

Author: AurelienBesnier

scenes/MeshView.tscn

@@ -0,0 +1,24 @@
+[gd_scene format=3 uid="uid://w8375y4hfvw0"]
+
+[ext_resource type="Script" uid="uid://dusuxv2yqo31o" path="res://scripts/mesh_loader.gd" id="1_4ebgs"]
+[ext_resource type="Script" uid="uid://demefs1tns4yw" path="res://addons/goutte.camera.trackball/trackball_camera.gd" id="2_ae8pf"]
+[ext_resource type="Shader" uid="uid://dojlkwvd3613r" path="res://shaders/eye_light.gdshader" id="2_xp361"]
+
+[sub_resource type="ShaderMaterial" id="ShaderMaterial_r74bk"]
+render_priority = 0
+shader = ExtResource("2_xp361")
+shader_parameter/albedo = Color(0, 0.735357, 0, 1)
+shader_parameter/shininess = 24.0
+
+[node name="MeshView" type="Node3D" unique_id=2065950553]
+
+[node name="MeshInstance3D" type="MeshInstance3D" parent="." unique_id=279862154]
+script = ExtResource("1_4ebgs")
+material = SubResource("ShaderMaterial_r74bk")
+
+[node name="TrackballCamera" type="Camera3D" parent="." unique_id=419741164]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 5)
+script = ExtResource("2_ae8pf")
+zoom_strength = 5.0
+zoom_maximum = 1000.0
+metadata/_custom_type_script = "uid://demefs1tns4yw"

scripts/mesh_loader.gd

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+extends MeshInstance3D
+
+@export
+var material: ShaderMaterial
+
+@onready var camera = $"../TrackballCamera"
+
+func _ready() -> void:
+	var test_path := "res://assets/Archicrop.obj"
+	var imported_mesh = load_obj_at_runtime(test_path)
+	if imported_mesh:
+		self.mesh = imported_mesh
+		self.mesh.surface_set_material(0, material)
+		update_camera_position()
+	else:
+		print("Error reading OBJ file")
+
+func update_camera_position():
+	var max_position = self.mesh.get_aabb().get_longest_axis_size()
+	var initial_position = camera.position
+	camera.position = Vector3(initial_position.x,initial_position.y,max_position)
+
+func load_obj_at_runtime(file_path: String) -> ArrayMesh:
+	var file = FileAccess.open(file_path, FileAccess.READ)
+	if not file: return
+	var text = file.get_as_text()
+	file.close()
+
+	var vertices: PackedVector3Array = []
+	var uvs: PackedVector2Array = []
+	var normals: PackedVector3Array = []
+	
+	var st = SurfaceTool.new()
+	st.begin(Mesh.PRIMITIVE_TRIANGLES)
+
+	var lines = text.split("\n")
+	for line in lines:
+		line = line.strip_edges()
+		if line.is_empty() or line.begins_with("#"):
+			continue
+			
+		var parts = line.split(" ", false)
+		var line_type = parts[0]
+
+		match line_type:
+			"v": # Position
+				vertices.append(Vector3(float(parts[1]), float(parts[2]), float(parts[3])))
+			"vt": # UVs
+				# OBJ Y-axis for UVs is inverted compared to Godot
+				uvs.append(Vector2(float(parts[1]), 1.0 - float(parts[2])))
+			"vn": # Normal
+				normals.append(Vector3(float(parts[1]), float(parts[2]), float(parts[3])))
+			"f": # Faces
+				if parts.size() == 4:
+					_add_face_vertex(parts[1], vertices, uvs, normals, st)
+					_add_face_vertex(parts[2], vertices, uvs, normals, st)
+					_add_face_vertex(parts[3], vertices, uvs, normals, st)
+				elif parts.size() == 5:
+					_add_face_vertex(parts[1], vertices, uvs, normals, st)
+					_add_face_vertex(parts[2], vertices, uvs, normals, st)
+					_add_face_vertex(parts[3], vertices, uvs, normals, st)
+					
+					_add_face_vertex(parts[1], vertices, uvs, normals, st)
+					_add_face_vertex(parts[3], vertices, uvs, normals, st)
+					_add_face_vertex(parts[4], vertices, uvs, normals, st)
+
+	if normals.is_empty():
+		st.generate_normals()
+	if not uvs.is_empty():
+		st.generate_tangents()
+
+	return st.commit()
+
+func _add_face_vertex(token: String, vertices: PackedVector3Array, uvs: PackedVector2Array, normals: PackedVector3Array, st: SurfaceTool) -> void:
+	var indices = token.split("/")
+	if indices.size() > 1 and not indices[1].is_empty():
+		var uv_index = int(indices[1]) - 1
+		if uv_index < uvs.size():
+			st.set_uv(uvs[uv_index])
+
+	if indices.size() > 2 and not indices[2].is_empty():
+		var normal_index = int(indices[2]) - 1
+		if normal_index < normals.size():
+			st.set_normal(normals[normal_index])
+
+	var vertex_index = int(indices[0]) - 1
+	if vertex_index < vertices.size():
+		st.add_vertex(vertices[vertex_index])

shaders/eye_light.gdshader

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+shader_type spatial;
+render_mode blend_mix, depth_draw_opaque, cull_disabled, unshaded;
+
+uniform vec4 albedo : source_color = vec4(1.0);
+uniform float shininess = 0.24;
+
+void fragment() {
+	vec3 camera_dir = vec3(0.0, 0.0, 1.0);
+	vec3 view_normal = normalize((VIEW_MATRIX * vec4(NORMAL, 0.0)).xyz);
+	
+	if (!FRONT_FACING) {
+		view_normal = -view_normal;
+	}
+	
+	float diffuse = max(dot(view_normal, camera_dir), 0.0);
+	float specular = pow(max(dot(view_normal, camera_dir), 0.0), shininess);
+	vec3 final_color = (albedo.rgb * diffuse) + vec3(specular * 0.4);
+	
+	ALBEDO = final_color;
+}