Cordel from United States  [7 posts]
13 year
I ran across this module last night but couldnt find any help info for it.
Is this module still in development? If not, will this allow to to measure the distance a blob ID is from a given camera?
Anonymous 13 year

The module is stable but the solution was not, in our opinion, insufficient for general use. We have been investigating alternative techniques but nothing yet ready for launch.

But in your case with a blob you can determine the distance from the camera at much greater speed if you are detecting a specific blob. Namely, detect the blob in both images (assuming stereo images) and then determine the offset difference of the COG of both blobs. This offset is proportion to the distance of the object from the camera (i.e. disparity).

Have a look at


for more information or provide the two stereo images and we can provide a sample robofile. (please also note what object you are extracting to create a blob)

Cordel from United States  [7 posts] 13 year
The robo file in that thread is very helpful.

One thing that is limiting though, is the fact that Center of Gravity subtraction between 2 stereo images will only work if your trying to get the distance for just 1 object. Having multiple objects would throw it off. My grand goal is to track 5-10 targets.

Actually my project is this. I am going to be tracking soap bubbles. Neutrally boyant, helium and smoke filled smoke bubbles. As they float around my bedroom, I am going to have 5-10 Lazer pen pointers that lock on and shoot the individual smoke bubbles, which will cause them to illuminate like an orb creating an amazing effect. Since i will have several servo turrets spread across a board, the trigonometry and distance of the bubbles from the camera will be important so I can shoot them accurately. I would like to be able to track/shoot 5-10 bubbles at a time
Anonymous 13 year

Can you include a stereo pair of images for multiple bubbles? It is possible to use this technique to compare more than one object in the image but it requires a little more checking. This is not unlike what our Blob Tracking module performs on subsequent images. Ie if two detected blobs have similar shape, are on the same Y axis (colinear requirement of stereo) and are perhaps a similar color then they can be matched and distance calculated. If you can provide some images we can probably create a module which would perform this matching and the distance to each object automatically.


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