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[DPRG] Re: Games
Subject: [DPRG] Re: Games
From: Chris Jang
cjang at ix.netcom.com
Date: Wed Jun 20 00:35:51 CDT 2007
>What a neat floor - and the CdS cells on the claw sure worked well.
>
>I'm just chiming in with some feedback about Drifter's chances of detecting
>the lines on that floor with the camera.
>
>The current vision system is exclusively blob based and it expects well
>defined and saturated hues on the target. Pushing the system to detect off
>white and white, or black, involves shifting the detectable color model on
>the brightness axis to such an extent that brightness info overwhelms hue.
>Every shadow then looks like a black target. At the other end of the scale
>every reflection, light source, white wall, and light color will merge to
>become a target blob.
>
>Using the camera Drifter would follow the those lines for a short distance
>and then would take off chasing a reflected light source. Shiny black looks
>nearly identical to white and this floor will likely need a different vision
>library or some line sensors.
A lot of early road segmentation research used luminance images only.
In practice, I've found that the combination of luminance and chrominance
is really necessary. This is reflected in computer vision systems such as
on Stanford's Grand Challenge robot that work directly in RGB color space.
Their classification of shadow areas is based on a combination of reduced
luminance and blue dominating red and green. For an environment like the
Science Place with a mixture of natural and artificial light, it would
probably be different.
This gets on to how at least some real world vision systems actually work.
One way around the problem is to have your own light. Some systems that
appear purely passive actually have IR illuminators to try and mitigate
the effect of ambient light.
For instance, the interactive signage you might see at a shopping mall,
those systems use an IR illuminator next to the camera. Some installations
might be near large windows which will always tend to cause problems for
vision systems as sunlight changes. The active source can compensate. Also
note the display surface is a special material with high reflectance.
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