How much contribution justifies being a co-author of paper
The standards for co-authorship vary greatly from field to field.  In some fields, you can be a co-author merely by supplying a useful reagent, where in others you need to be much more heavily involved with the actual work.  I don't know what the culture for computer graphics in particular is, but no matter how you draw the line, the general principle is the same everywhere:

The authors of a paper should be precisely the people who meaningfully contributed to the success of the work.

Some advocate for the tighter definition laid out in the Vancouver Protocol, which requires every author to be a significant writer of the paper as well.  That, however, has some serious problems, particularly in tending to unfairly exclude students from authorship.

Applying this to the case of your authorship, the answer is not immediately obvious from your question whether you should be an author or be named in an acknowledgements section, because it depends on the value of the work that you did and that's something that only you and your co-authors are in a position to just.  For example, if your work with the data set was just reformatting it from one format to another, then it's clearly not worth authorship.  If you did some real curation of the data set, e.g., evaluating the information to remove artifacts, and this made a big difference in obtaining the results, then authorship is certainly reasonable.  Note that the amount of work that you did is not actually a good measure: if you whipped up a curation script in a few hours and then let it run, it's no less valuable than spending months inefficiently curating by hand.

Finally, it's fine to err on the side of inclusiveness.  If your contributions are a borderline case, and the primary authors found your work valuable enough to merit a co-authorship, nobody will be hurt by including you in a minor author position in the author list.