I need a program to make a 3D drawing easy and carefully at a half of a day.
3D drawing consists of:
1 vectors,
2 lines,
3 arcs for angle between two vectors or lines vector,
4 vector, line, arc labels.
Label requirements:
1 Greek symbols (phi, alpha, theta, ...)
2 showing a fraction ability (phi/2)
3 font style such as italic, bold, ...
I need to insert this drawing in my paper, but it will be great if an editor allow to watch the image in 3D.
If you don't mind doing some programming, I would consider Sketch. It provides a nice high-level programming language that can be used to generate TikZ code that you can directly compile into a PDF or a vector graphics file.
Since it's designed to interoperate with LaTeX, it will also give you the ability to include Greek letters and mathematical symbols in your 3D drawings (this was part of the requirements of the question)
You can see some examples here. Here is an example from their website:
A very easy 3D sketching tool is Google SketchUp.
"SketchUp is the finest (and most innovative) tool available for anyone designing anything from coffee pots to skyscrapers." – McCall & Associates
Continuing the Open Source tradition established in the present answers and comments, I'll hereby suggest the vector graphics editor Inkscape:
It will definitely do what you want, and the many features should make the learning curve worthwhile to climb - here's an Inkscape tutorial for 3D.
EDIT: for Greek letters, maybe you'll need to type the Unicodes [PDF] by first typing Ctrl+U.
You need Math illustrations. They are in 2D now but for the feature...In Math illustrations you can create constrained sketch like in Solidworks.So you don't need static snaps like in old Autocad,Adobe Illustartor,Inkscape and many other stupid modern programs wich don`t create and keep relations between objects.
