Oh also one other thing to mention - one way to get a line on "both sides" right now is to drag out a construction line.
When you drag out a construction line, the "endpoints" of the construction line are available as snaps, so that lets you build the line like you want.
So for example say you have this line:
And you want to draw another one at the end from the midpoint, making a T shape.
To do that, start up the Line command, and move your mouse to the end, like this:
But instead of clicking the point there to place the start of the line, instead press down, and hold down and drag - that creates a construction line instead of placing the point. Drag the line downwards along the perpendicular, like this:
Release the mouse where you want the start of your "T" cross line to begin. Now that construction line will have an "end" snap right there where you can click for the start point of your line, and then one cool feature of construction lines is that it gives you that same distance between the cline start and end points reflected on to the other side, so you can go over here:
And find another "end" snap there to place your line in the straddling position that you wanted:
This is the main reason why MoI doesn't have all those line options like Rhino does - all of those things can generally be handled by using construction lines instead.
The cool part of this is that construction lines are available to any drawing command when you are placing a point, not just as special options just within a particular Line command.
However, I don't think it is bad to add a "Both sides" option to line anyway, I don't think it will be a problem to add that in for v2.
But once you get used to construction lines, I think you should find it pretty quick to make this kind of thing using them. There are also a lot of other options like capturing a direction or distance and applying it to a new location (kind of like a measuring stick) - setting up divisions like 1/3 of the way between 2 points, quickly getting the midpoint between 2 points, projecting a point to be equal height to something existing object, dragging z-lines to place points at a height above the plane in the 3D view, getting quick extension and intersection lines, .... see here for some details:
http://moi3d.com/1.0/docs/moi_command_reference10.htm#constructionlines
- Michael