Instructions:

• Add DrawLine3D.gd to the Godot AutoLoad list
• Call DrawLine3D.DrawLine, DrawLine3D.DrawRay, or DrawLine3D.DrawCube from any script

OR

• Add an instance of the DrawLine3D to the scene:

var LineDrawer = preload("res://DrawLine3D.gd").new() #In 'global' scope  
...
add_child(LineDrawer) #At some point before calling the desired draw function(s) e.g. in '_ready()'

• Call LineDrawer.DrawLine, LineDrawer.DrawRay, or LineDrawer.DrawCube from the script that created the DrawLine3D node

DrawLine parameters: start point, end point, color, time (optional)
DrawRay parameters: start point, velocity (direction and magnitude), color, time (optional)
DrawCube parameters: start point, half extents (float), color, time (optional)

Examples

• DrawLine3D.DrawLine(Vector3(0, 0, 0), Vector3(1, 2, 0), Color(0, 0, 1), 1.5) Draws a line from (0, 0, 0) to (1, 2, 0) colored blue and will last for 1.5 seconds
• DrawLine3D.DrawCube(Vector3(0, 1, 0), 0.5, Color(1, 0, 0)) Draws a cube at (0, 1, 0) with a half extent size of 0.5 and colored red