private fun read_face_index_set(face: ObjFace): Bool
	do
		var token = read_token

		var parts = token.split('/')
		if parts.is_empty or parts.first.is_empty then return false

		var v = new ObjVertex
		for i in parts.length.times, part in parts do
			part = part.trim

			var n = null
			if not part.is_empty and part.is_numeric then n = part.to_i

			if i == 0 then
				n = n or else 0 # Error if n == null
				if n < 0 then n = geometry.vertex_points.length + n
				v.vertex_point_index = n
			else if i == 1 then
				if n != null and n < 0 then n = geometry.texture_coords.length + n
				v.texture_coord_index = n
			else if i == 2 then
				if n != null and n < 0 then n = geometry.normals.length + n
				v.normal_index = n
			else abort
		end
		face.vertices.add v

		return true
	end