pic: Three Trackballs?

After one of the practice matches at the San Diego Regional, there appeared to be five trackballs on the field. Here are three of them.

During one of the quarter finals or semis in San Diego Beach Bots was working on a ball which popped, about 30 seconds later a referee replaced it with another track ball.

Those reflections are SO BAD at the end of the field…

Sometimes you avoid things that arent there… sometimes you don’t avoid things that are there… :ahh:


I didn’t notice it too badly at Oregon, but then again I wasn’t driving…

You have to be behind the glass to see it. It can be brutal.

I totally fell for the “avoiding thing that arent there and running into things that are there” thing. thats why i always wanted to get the #2 position! its the best spot ever, you get to see both sides of the field!:smiley:

Trust me, there was plenty of reflection at Oregon. It’s very annoying.

I remember one match when I got all excited because it didn’t look like the Blue Alliance was fielding any robots. Then I realized it was just the reflections… :o

This is one of the reasons why I do not fully agree with the current state of G22. While setting up the field at the Connecticut Regional today, I noticed the large “blind spots” when trying to look through the lane divider diagonally.

Warning: Science Content! Basically what is happening is that when light passes through a transparent medium (such as in our case, the polycarbonate), there is always an angle (called the critical angle) as which light stops refracting through the medium and starts reflecting off the medium. As it happens, the low “angle of incidence” at which we try to look through the polycarbonate towards the opposite corner of the field is greater the “critical angle”. This causes what we perceive to be behind the polycarbonate to actually be a reflection of what we see on one’s side at the far end of the field. Thus, we end up with a large blind spot where we cannot see anything on the far corner of the field.

As such, I can easily see how a driver would now have no idea where there robot might be in this blind spot, and how easy it can be for them to inadvertently back up too much (and accidentally cross the lane marker) before they can correct what is going on.

Having seen the field first hand I will say that the reflections are quite bad–At times our drive team thought that an alliance was fielding four robots and it can be quite disconcerting to see two of your robot racing down the lane. It seems that the drivers stations are in the perfect position for these reflections as when acting as robocoach I experienced no problems and the audience doesn’t see them.

Now the real question is

Do you think FIRST and the GDC did this on purpose? Or is this just as unexpected to FIRST as it is to the people who have to drive the robots :)?

I think it’s an unintended consequence. It varies from arena to arena, depending on the lighting conditions. Wherever the prototype field was set up, it may not have been so bad.

It’s a variant of Pepper’s Ghost, a simple trick developed by Henry Dircks in 1862. If you’ve gone to Disney’s Haunted Mansion you saw it in the huge Ballroom scene.

BTW I remember seeing photos somewhere on CD showing this effect on the field and how robots vanish.

I hate to pimp, but we talk about this a bit in the latest episode of FIRSTcast…

Here is the thread with the pictures.

Thanks Phyrxes. Gosh, no wonder I couldn’t find it – wrong thread name, wrong poster. It’s a wonder I can find my way out of bed in the morning…

Looking at those photos again I wonder why they even have those upper panels. The bottom ones I could see, if only for sonar and to match the outside walls. Come to think of it, the outside outside “protector” walls (if you follow me) don’t have the panels. Wouldn’t it be easier to make a rule “no robots can go thru the wall”? Well, it makes for good post-season rule changes.

actually all sides should have panels - outside walls and the divider (basically everything in the center of the field both inside and out have panels… I think…

whats sad is I put this field together and I can’t remember for the life of me if there was a side w/o them. A sign of old age :-p and too many field put together.

2003…Oh wait, this is 2008.

Every side has panels. Two have diamond-plate and Lexan panels, four have chain-link panels (this year), and the remaining ones have Lexan on pipes. Even the gates have panels; those are just easily movable by a human.

I could have sworn the field at VCU did not have polycarb on the pipes making up the outside perimeter (at least on the side nearest the stands).

Now you guys have got me wondering. A quick search found me this photo which may exhibit my thinking.

The ends of the field where the drivers are have the big lexan panels. The angled corners are the chainlink fence. The center divider are 3 high lexan panels. The low outside sidewalls have lexan, but the outer outside walls are just the metal pipe - no lexan. At least I can’t see any. There are no zip-ties holding the panels anyway, like the center divider wall has. I remember at the end of Final matches before the awards they were taking the pipes down on the audience side but no lexan.

I realize there is a need for a protector/divider both at center divider and the long side walls, to keep the trackballs from going all over the place, but the lexan? Keeping robots on own side? Make a rule against it, or add another horizontal pipe. Entangling? Well, the robots do that now on the overpass. I’m sure there was a reason. :confused:

I always figured it was to prevent manipulators and/or robots from “trying” to go through the center divider, that is the drive base goes under the lowest section of horizontal pipe and your manipulator gets demolished as your entire robot attempts to take a “short cut.” It also presents a “solid” object on the “left” to bounce ultrasonic range finders off of.