This is a small debug drawing script, which you can setup as an auto-load singleton. It lets you print text on the screen, draw boxes or lines from anywhere in your code. It is mostly geared towards 3D at the moment.
Once installed under addons/zylann.debug_draw, add the debug_draw.gd script as an auto-load to your project and start using it as a singleton.
Example with a singleton named DebugDraw:
func _process(delta):
# Some test variables, usually you'd get them from game logic
var time = Time.get_ticks_msec() / 1000.0
var box_pos = Vector3(0, sin(time * 4.0), 0)
var line_begin = Vector3(-1, sin(time * 4.0), 0)
var line_end = Vector3(1, cos(time * 4.0), 0)
DebugDraw.draw_box(box_pos, Vector3(1, 2, 1), Color(0, 1, 0))
DebugDraw.draw_box_aabb(AABB(Vector3(3, 0, 0), Vector3(2, 1, 1)), Color(0, 1, 0.5))
DebugDraw.draw_line_3d(line_begin, line_end, Color(1, 1, 0))
DebugDraw.draw_axes(Transform3D(Basis().rotated(Vector3(0,1,0), time), Vector3(-2, 0, 0)))
DebugDraw.draw_cube(Vector3(-1, 2, 0), 0.1, Color(sin(time * 10.0) * 0.5 + 0.5, 0.5, 0.5))
var cube_trans = Transform3D(
Basis().scaled(Vector3(2,1,0.5)).rotated(Vector3(0,1,0), time).rotated(Vector3(1,0,0),
0.5*time), Vector3(-3.5, 0, 0))
DebugDraw.draw_transformed_cube(cube_trans, Color(1,0.5,0))
DebugDraw.set_text("Time", str(time))
DebugDraw.set_text("Frames drawn", str(Engine.get_frames_drawn()))
DebugDraw.set_text("FPS", str(Engine.get_frames_per_second()))
DebugDraw.set_text("delta", str(delta))
DebugDraw.draw_mesh(_mesh,
Transform3D(Basis().rotated(Vector3(1,1,0.5).normalized(), time), Vector3(3.5,0,3)),
Color(0.5+0.5*sin(time*2.0), 0.5+0.5*cos(time*2.0), 1.0))