Dual cameras for better results in Photoscan

[Photogrammetryfacts]

So I came over this interesting blog post today:

http://blog.kiteandlightning.la/breakthrough-a-3d-head-scan-using-one-camera/

Here the author claims that using "stereo pairs when using photogrammetry results in superbly clean meshes".

Have anyone tried something like this?

[Kiesel]

Yes, Mark Florquin with three cameras see:http://www.agisoft.com/forum/index.php?topic=970.msg4733#msg4733

Karsten

[Marcel]

There is a difference between subject matter:

If you are doing human scans then multiple cameras will be better (faster acquisition so less movement between photos).

If you do fully static objects then a single camera will give you exactly the same quality as using multiple cameras.

Capturing with two cameras at a known distance from each other has no benefit in Photoscan (apart from capturing twice as fast). This distance information is not used so you do not gain processing speed or accuracy.

[Alexey Pasumansky]

Capturing with two cameras at a known distance from each other has no benefit in Photoscan (apart from capturing twice as fast). This distance information is not used so you do not gain processing speed or accuracy.

In PhotoScan Pro version 1.1.0 it is possible to create scale-bars between pairs of camera centers and use this information for scaling and optimization purposes. However, the stereobase should not be negligibly small compared to the distance to object.

[Kiesel]

Of course the better scan quality came in this case from no movement between shots. The use of the known distance between cameras inside PhotoScan was an old feature request and seams now been implemented, thank you to Agisoft team. Another advantage is besides faster shooting that you have allways working stereo or triple pairs.

Karsten

[Marcel]

Capturing with two cameras at a known distance from each other has no benefit in Photoscan (apart from capturing twice as fast). This distance information is not used so you do not gain processing speed or accuracy.

In PhotoScan Pro version 1.1.0 it is possible to create scale-bars between pairs of camera centers and use this information for scaling and optimization purposes. However, the stereobase should not be negligibly small compared to the distance to object.

Hey, that is awesome!

Could you tell us what the actual effect is on processing speed and quality?

[Photogrammetryfacts]

There is a difference between subject matter:

If you are doing human scans then multiple cameras will be better (faster acquisition so less movement between photos).

If you do fully static objects then a single camera will give you exactly the same quality as using multiple cameras.

Capturing with two cameras at a known distance from each other has no benefit in Photoscan (apart from capturing twice as fast). This distance information is not used so you do not gain processing speed or accuracy.

Well consider this: If you take 40 shots of a model "free handed", chances are that some images might not align properly or that the angle or distance makes for various numbers of points successfully generated between image pairs. Now if you have two cameras positioned in an ideal angle, the success rate for these image pairs will always be 100%, though between n image pairs there might still be variance in terms of the number of successful points. I'll hypothesize that on average you'll get more points generated with a dual camera rig than a single camera with equal numbers of pictures in the data set. And I'll hypothesize that this will be true no matter if the subject is static or moving slightly. Do anyone know the ideal angle between two cameras BTW?

Capturing with two cameras at a known distance from each other has no benefit in Photoscan (apart from capturing twice as fast). This distance information is not used so you do not gain processing speed or accuracy.

In PhotoScan Pro version 1.1.0 it is possible to create scale-bars between pairs of camera centers and use this information for scaling and optimization purposes. However, the stereobase should not be negligibly small compared to the distance to object.

Do you know if there is any good documentation on this? I want to try it out, but I'm not sure I completely understand how it's supposed to work. Also, do you know the ideal positioning of the two cameras?

[Kiesel]

Now if you have two cameras positioned in an ideal angle, the success rate for these image pairs will always be 100%, though between n image pairs there might still be variance in terms of the number of successful points. I'll hypothesize that on average you'll get more points generated with a dual camera rig than a single camera with equal numbers of pictures in the data set. And I'll hypothesize that this will be true no matter if the subject is static or moving slightly.

That was meant with the advantage of "allways working stereo pairs".

Do anyone know the ideal angle between two cameras BTW?

It is a compromise of ideal intersection angle (a little bit more than 90 degrees) and better feature matching with closer angles. But generally the ratio between stereo base and distance should be in the rang of 1/5 to 1/10.

Karsten