I do a research for a 3d CAD open format.
Can I use COLLADA for this reason?
I will create my own OpenGL CAD renderer, so I don’t care about implementations.
The question is only about specification. Can I use COLLADA for CAD purposes?
SVG is good enough for me but it is only 2D, so I must reject it.
COLLADA 1.5 is the core component of automationML, http://www.automationml.org/ , an interchange XML standard for the automation (robot) industry, used in car manufacturing for instance. the Automation ML group has some software (.NET/C#) that may be useful to you, you may want to contact them.