12-03-2008 22:53

chaoticprout

Re: pic: Three Trackballs?

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.

12-03-2008 23:01

Qbranch

Re: pic: Three Trackballs?

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...

-q

12-03-2008 23:27

danshaffer

Re: pic: Three Trackballs?

I didn't notice it too badly at Oregon, but then again I wasn't driving...

12-03-2008 23:32

IndySam

Re: pic: Three Trackballs?

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

12-03-2008 23:39

Burnout

Re: pic: Three Trackballs?

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!

12-03-2008 23:42

=Martin=Taylor=

Re: pic: Three Trackballs?

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....

13-03-2008 00:14

artdutra04

Re: pic: Three Trackballs?

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.

13-03-2008 00:19

Matt H.

Re: pic: Three Trackballs?

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.

13-03-2008 06:14

mtaman02

Re: pic: Three Trackballs?

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 ?

13-03-2008 06:27

GaryVoshol

Re: pic: Three Trackballs?

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.

13-03-2008 08:47

Roger

Re: pic: Three Trackballs?

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.

13-03-2008 09:46

Joe Matt

Re: pic: Three Trackballs?

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

http://www.chiefdelphi.com/forums/sh...ad.php?t=65621

13-03-2008 09:52

Phyrxes

Re: pic: Three Trackballs?

Here is the thread with the pictures.
http://www.chiefdelphi.com/forums/sh...5&postcount=52

13-03-2008 10:49

Roger

Re: pic: Three Trackballs?

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.

13-03-2008 11:11

mtaman02

Re: pic: Three Trackballs?

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.

13-03-2008 11:20

EricH

Re: pic: Three Trackballs?

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.

13-03-2008 11:26

Phyrxes

Re: pic: Three Trackballs?

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).

13-03-2008 12:14

Roger

Re: pic: Three Trackballs?

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.

13-03-2008 12:55

Phyrxes

Re: pic: Three Trackballs?

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.

13-03-2008 14:16

EricH

Re: pic: Three Trackballs?

Oh, the OUTSIDE ones! I was thinking of the normal field walls. You're right, those don't have any visible. I'd say that's so refs, spectators, and camera people have a clear view with no chance of reflection.

14-03-2008 03:39

KarenH

Re: pic: Three Trackballs?

You're both correct. The center wall has larger diameter pipes, and the reflective panels are laced in place with substantial cable ties. The look reminds me of leathercraft projects from childhood day camps (moccasins?). The bases for the uprights are covered with carpet pieces. The thing is a bit of a nuisance to assemble, and the cable ties are a nuisance when taking it down, but it looks to me like the greatest nuisance for the field crew is keeping the carpet pieces securely taped down. One robot in San Diego ate one of the carpet pieces, along with the sticky tape, and got "indigestion."

The bases of the outer walls are placed outside the normal side rails of the field. The outer walls have no polycarbonate panels, and have smaller diameter pipes than the inner walls. They also require little or no maintenance during the competition.

From the differing construction, I conclude that the purpose of the center divider is to prevent both trackballs and robots from crossing the center of the field, so it has to be strong enough to withstand lots of rough treatment. But the purpose of the outer fences is merely to keep the trackballs from escaping. So they are neither as robust nor as impermeable as the center divider.

Furthermore, I suspect that the GDC knew very well what the effect of reflective panels would be. After all, they DIDN'T use the stuff on the corner panels.

14-03-2008 05:48

Chief Samwize

Re: pic: Three Trackballs?

the reflections on the opposite end of the field are extremely distracting. When driving into the other corner its like going in blind. During a practice match I ran into our own partners, who I didn't see, that were trying to pick up the ball.

Oh well, just another element to the game.

-Sam

14-03-2008 09:21

Roger

Re: pic: Three Trackballs?

The corner chainlink panels -- wasn't that so the IR can go thru it? But I agree GDC must have seen (or not ) how the center panels act. But I don't think they purposely designed it that way: they probably figured it would be part of the game -- a classic "it's not a bug -- it's a feature!"

I would think if the middle row of panels were removed and another horizontal bar put in would be a better alternate -- do not cross or you will get entangled (or get your parts sliced off!) might be enough of a punishment. I'm thinking of all those robots that tangled up in the overpass.

The sonar can still bounce off the bottom panels, either the inside wall or the outer wall. After all, the outside wall is low anyway.

Last night I tried standing in front of our drivers as they practiced. They got annoyed until I show them those photos. "Oh yeah..." Then we tried the "use the force Luke" approach -- close your eyes and use verbal commands only. Good thing our Robo-Coach has those hand-signals...

Methinks that hat is on too tight EricH ; but I did fear my "the outside outside 'protector' walls (if you follow me)" didn't quite emphasize which I meant.

14-03-2008 12:18

ReaperGoat

Re: pic: Three Trackballs?

Oh man...that's just...ridiculous

Couldn't they have made the top two out of the chain link fencing they used on the Robo-Coach stations? Or chicken wire, even? There are better ways to keep robots from going through without killing the visibility and putting teams at a disadvantage.

14-03-2008 14:19

Jeff Waegelin

Re: pic: Three Trackballs?

Could they have? Yes, of course. But then we would probably be complaining about robots getting caught in the fencing/chicken wire instead of visibility. I am sure the GDC considered their options, and decided that (even with its flaws) the Lexan was the best choice for drivers, spectators, and robots.

14-03-2008 17:22

ZInventor

Re: pic: Three Trackballs?

i can't remember what the stuff's called, but i know that somewhere, i've seen a type of plastic that lets you see through at any angle, and just plain refuses to reflect or refract light.

i've used the stuff at a tech museum (OMSI) where i volunteer, and it's a pain, since the only part of it that you can see are fingerprints on the serface whenever we use it, we have to wash it in windex so that it doesn't look like there are fingerpeints floating in mid air...

i think it's the same stuff they use in stop-motion movies when they have to make something appear to fly

if FIRST had been able to use that stuff (which is just as strong as lexan) instead, itwould be SOOOOOOOOOOOOOO much easier to controll the bot on the lane you currently can't see... lols...

Z

14-03-2008 20:00

GaryVoshol

Re: pic: Three Trackballs?

Remember that if you are in your home stretch and you should poke an appendage through the proposed perforated lane divider, you would have generated a 10-point penalty for breaking the plane. The lane divider is directly above the lane marker.

I noticed something in the animation today - there doesn't appear to be any panels in the lane divider. Whether this was an oversight, the initial field design, or just too hard to animate, I wouldn't know.