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Lighting
Anonymous
10 years
Hi guys,

I'm using this software to control my Lego NXT and having great fun with it.  It's great for autonomous machines.   I was wondering what's lighting conditions give the best results.  I find that my robot is very picky about shadows, lighting intensity etc.

Thanks,
PT

Lighting, lighting, lighting!!
Anonymous
10 years
PT,

Lighting is perhaps the biggest issue in computer vision. This will make or break your vision algorithm and there is not any full proof way to avoid lighting issues completely. This will also be based on what you are trying to accomplish. For example, color in different lighting appears as a different color! Our brain has a way of adapting to that (think of putting on colored sun glasses ... after a while you don't notice the green or blue hue anymore until you take them off!). The most robust lighting techniques normally have their basis in edge detection since a light edge and a dark edge can still be considered an edge ... but even then a threshold in normally used which is somewhat dependent on lighting!

RoboRealm allows you to experiment around with different modules to try and eliminate the lighting considerations but so far those are mainly dealing with pixel manipulations. The larger solution will have to work at a higher level that can understand a shadow is over part of an actually coherent object. This requires many more factors to be included in segmentation which is a very active area of research and something that we are also involved with. Perhaps in the future we will have something that will better deal with shadows and lighting adjustments ... but that will not be for a while!

STeven.

Lighting
Anonymous
10 years
Cool.  Like I said, I'm more interested in autonomous robots rather than fixed, production-like machines.  I always jump in the deep end.  I have a project on the go that I hope to post soon.  Looking forward to further developments on your side!

Thanks Steve.
Lighting
Anonymous
10 years
Cool.  Like I said, I'm more interested in autonomous robots rather than fixed, production-like machines.  I always jump in the deep end.  I have a project on the go that I hope to post soon.  Looking forward to further developments on your side!

Thanks Steve.
Lighting trick
Pt from Ireland  [2 posts]
10 years
Hi Steve,

I was wondering if it was possible to trick our robots to make them less sensitive to changes in light?  What if we had a material that absorbs a lot of light on objects we want to trace.  Add some thresholding and negative filter.

Then, regardless of lighting levels, only the piece of light-absorbing material would be visible to  the machine.  

What do you think?  Any ideas what material to use?
Anonymous 10 years
Well first off you would not have to invert it, the threshold would simply have to be for dark objects. However, i doubt that this would really help with the lighting problem... e.g. If the lens gets hit by direct sunlight after beeing adjusted to a dark room, the object you want to track disappears for some time while the camera re-adjusts. You can try to prevent this by putting barn doors around your camera.

The most light absorbant material i can think of is black molleton felt, like it is used for backdrops in theater. However i doubt that it will allways look the same for a web-cam. Another possibility would be to go to the "bright" side and have the object you want to track send out infrared light in all directions (CMOS webcams are sensitive to it and "see" it as bright white, im not sure about CCD sensors)...

When detecting shapes, humans have one major "hardware" benefit to most machines, we can see in stereo. So we can not only distinguish between hue and intensity differences but also depth. Processing wise, the human brain is much more flexible than any non-Ai coputer, so besides basic edge detecting, shape matching, and COG calculations there isnt allot you can do.

About the shadows... I am currently working on a convolution-like filter looking for simulatinous decreases in RGB (shadows :) ) and then lighting them up, however i lack programmen skills to really get this to work...

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