I have the following problem. Suppose I have a 3D triangle in world coordinates, and I know their corresponding projected image coordinates. Is it possible to find the view and projection transform?

The image points are actually found by feature point detection algorithm, which is why I do not know the view/proj matrices. But I want to project more 3D points, which is why I need to solve/approximate the view/projection matrices.

You generally need the images of 5 points to determine a projective transformation, since a projective frame for a 3-dimensional projective space has 5 points.

I might be able to get 5. Do you have a link for solving for this projective frame?

Searching the web, this is the first relevant thing I found: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=26&ved=0ahUKEwi905aElfXTAhUBQCYKHe12CMMQFgi-ATAZ&url=http%3A%2F%2Fwww-ljk.imag.fr%2FPublications%2FBasilic%2Fcom.lmc.publi.PUBLI_Inproceedings%401176ddd04d5_1b01047%2FTriggs-dlt-iccv99.pdf&usg=AFQjCNE5QZ_O2DgRUF_e5iYgOI7E6asTmg&sig2=tuzvfOj7e2EUKOtxB0_-DA

I can try to think of a solution myself, but it doesn't seem like a trivial problem.