Hi Njen,
Thanks for your post.
I would respectfully like to use this post as example to the forum community. When you're asking for support, please include a detailed description of the specific steps you've taken, what your objective is, and what the problems are that you're experiencing. It's also helpful to know which version of Terragen is being used, and including the TGD file and screen shots will go a long way to helping us diagnose the situation.
In this case, to say "...the motion vector output is not correct." doesn't provide a clue of how it was created and how you're intending to apply the 2D motion blur element in post production. In other words, we have make a lot of assumptions and take guesses at what "might" be the issue, instead of focusing on duplicating the problem to see if a bug really exists.
Again, I'm not trying to pick on Njen's support request and am quite happy to help solve any issues, but it seems that lately we've seen a number of posts that don't paint a complete picture of what the user is trying to accomplish.
Njen, I assume you're using Terragen 4 Professional and the render layers feature with Surface 2D Motion Vector and Cloud 2D Motion Vector outputs enabled. What version of Terragen 4 are you using, and what 2D software package are you using to apply motion vector data? What value range are you using in the 2D software package for the motion blur, and have you tried "extreme" values just to see if the motion blur data is being read by the 2D package?
Also, here's a link to the wiki documentation for compositing Terragen render elements, which includes a section on the 2D motion blur element:
https://planetside.co.uk/wiki/index.php?title=Compositing_Terragen_Render_Elements
