relative constraint with polylines drawing...

 From:  labuzz
547.1 

Hi,
Newbie here. I am a 3d real time artist mainly, my final output is polys. Very often I build a high poly mesh that is useful for things like normal map, backing...
Thats why I am interested by tools like MoI.
I would like to know if there's a fast way to draw a line segment ( 2d) with a relative constraint ( angular ) to the previous one ( not based on the world grid->straight snap ). To summarize, what is the fastest way to draw 2 perpendiculars( angular snap )?
Another question, is there a way to have a snap increment when you relocate(/reorient relative to the previous state) cline?
Is there any plan for an eps/ai importer ?
Possible to print in the future like in rhino4 ( very good scale control ) ?

I am french.
Tky.