collision detection with markers

[tailta1l]

Hi,
i'm a newbie with AR Toolkit, and would like some others to shed some light on the following problem.

we have 2 markers
1 marker produces a projected object.
and we intend to use the 2nd marker to catch that projected object.

so basically we are interested in determining whether the project object has collided with the 2nd marker.
is this possible with the current toolkit?

cheers

[tbuffry]

there is no such tools delivered with the artoolkit, you should try to get the markers positions and then compare the distance.

[Graham]

It is most likly something you will need to implement yourself. There are systems in the AR toolkit for recognising when markers are fixed together, but this is probably not what you want.

The only problem that can occur with directly comparing distances between markers is that the z-axis distance is often decieving.
Unless the camera is calibrated perfectly (which in reality is close to impossible to do) then you will not be guarenteed exact depth values. They may vary by a few cm.
This is understandable, because when a marker gets very small, a single pixel change in size can represent the marker being *significantly* further away from the camera.
What you may want to do is project the position of one marker (towards the camera) onto the plane of the other marker, and compare the intersection point to the centre of the other marker. This I am doing in one of my own projects for example.