I created a turtle in NetLogo which is moving randomly and there are some obstacles. Is it possible to get its current direction? I want to get the turtle to walk back to the center when it sees an obstacle. I can calculate distance to the center, but since I don't know its direction I can't say forward or backwards, for example.
The turtle's current direction is given by the heading variable. You can both read and write to this variable in order to change the turtle's heading. You can also change it using facexy as N. Payette mentioned.
The facexy primitive will allow you to set your turtle's heading toward the origin:
http://ccl.northwestern.edu/netlogo/docs/dictionary.html#facexy
ask turtle <who>
[If (patch-ahead = obstacle)
[
facexy origin
fd distance origin
]
]
Here obstacle and origin are the respective patches.
Building on what Jose M Vidal and N. Payette have already said.
Related
I want to know the Relationship between turtle size and patch size in Netlogo. Also I want to make those sizes in a way such that any turtle moves from one patch to another at every tick.
Patch size is measured in pixels. It is configurable in the "Model Settings" dialog.
You can think of turtle size as measured in "patches". A turtle of size 1 should appear to be the size of one patch. (Note, however, that turtle size is a "display only" property. Conceptually, turtles are just points. They don't really occupy space in the NetLogo world even if they appear to do so.)
Changing the xcor or the ycor of a turtle by 1 should move it by exactly one patch. If you want them to move diagonally, things are a bit more messy. You might be better off targeting destination patches directly, e.g.:
; move to the patch north-east of current position:
ask one-of turtles [ move-to patch-at 1 1 ]
; move to an adjacent patch at random:
ask one-of turtles [ move-to one-of neighbors ]
Those are just examples, of course. The code to use will depend on what exactly you are trying to do. If you tell us more in a separate question, we might be able to help you.
when we ask a turtle to forward 2, does it mean:
on its heading direction, move to the second nearest patch
on its heading direction, move to the second nearest patch's center point
on its heading direction, move to the second nearest patch's center point which is (pxcor, pycor)
which one is correct? or are they the same answer?
How do we define the nearest patch this turtle is pointing to? Is the following understanding correct?
top patch: if heading is between -45(315) and 45 degree
right patch: if heading is between 45 and 135 degree
bottom patch: if heading is between 135 and 225 degree
left patch: if heading is between 225 and 315 degree
It means to move forward a distance of 1. The easiest way to see this is with the following code:
to setup
clear-all
create-turtles 1
[ setxy 0 0
set heading 45
forward 1
print xcor
print ycor
]
end
Try changing the heading and see what happens. Note that patches are exactly 1 unit wide and the centre of the patch is at integer values (so patch 0 0 extends from xcor -0.5 to xcor +0.5)
forward totally ignores patch boundaries and patch centers, so 1–3 are all incorrect. Patches don't enter into it; it's just trigonometry on the turtle's x and y coordinates. Specifically, forward 1 just means setxy (xcor + sin heading) (ycor + cos heading). The destination patch is simply whatever patch the new x and y coordinates happen to lie within. The destination may or may not be a patch center.
forward 1 might leave the turtle in the same patch (e.g. if the turtle is in the southwest corner of a patch facing northeast; the length of the diagonal is 1.414..., so forward 1 isn't enough to reach a new patch). Or, forward 1 might take the turtle to the nearest patch ahead, or to the second nearest patch ahead. (The latter can occur if the turtle just grazes the corner of a patch.)
A good model to play with to explore and understand all of these possibilities is Next Patch Example, in the Code Examples section of NetLogo's Models Library
As for the second part of your question, your definition is only correct if the turtle is initially standing on a patch center. For the general case, Next Patch Example answers that too. The next-patch procedure in that model is like your definition, but handles the general case.
In order for two way traffic to flow along a road that is the thickness of a single patch it is necessary for the position of each turtle to be to either the left or the right of the patch on which they are travelling. How can I control where a turtle resides on a patch while travelling along it so that there is enough space for two opposing flows of traffic on the same road?
You can use set xcor ... and set ycor ..., or setxy ... ..., or any other turtle motion command such as fd or bk, to position the turtle however you like. If the turtle's coordinates are both integers, it's on a patch center. If either or both aren't integers, then the turtle is in some other location in the patch.
I have enclosed turtles in between walls and obstacles and want them to move to a specific goal spot. Each tick I forward turtle only a specific amount. How do I implement this in terms to variating the turtle heading?
Explaining more
In the above figure:
1. Consider all turtles inside the box at the start
2. You want turtles to reach goal spot above,(where turtles present currently in figure)
3. You have obstacles that is, walls in between which 1 opening that is the rectangle in the figure with the gap. Turtles have to pass this gap only.
How I tried
I make turtles face the goal spot using facexy and bounce back after colliding with wall but in doing so the turtles on extreme left and right of box keep colliding with wall since after each collision they again have the direction from facexy
Please help. Thanks in advance.
An easy fix (according to what I read about making the turtles bounce).
goal-xcor is the x-coordinate of goal.
goal-ycor is the y-coordinate
of goal.
random-number is a random number between 1 and 10(?).
`If COLLISION: `
if they're in the left make them facexy goal-xcor + random-number goal-ycor
if they're in the right make them facexy goal-xcor - random-number goal-ycor
If there is not any collision it means they're in the right way and they should keep going the goal direction.
It's important that you facexy goal-xcor goal-ycor every time you make them turn around. To be more clear: Pseudo-code:
1 setup-turtles-inside-box
loop:
2 ask all turtles to face goal.
3 ask all turtles to go forward.
4 if collision
5 if turtle-in-left
6 ask turtle to face goal-xcor + random-number goal-ycor
else
ask turtle to face goal-xcor - random-number goal-ycor
7 loop until all turtles are in goal.
Let us know of any doubt!
Here is another approach:
http://rur-ple.sourceforge.net/en/random.htm
A turtle reaches a point and for a set amount of time, can relate it's heading to other turtles within it's range.
Pseudo code
if any? turtles within 5
[pass on heading to other turtle]
The other turtle I'm assuming would need a call to use this heading, so something like
Pseudo code
if has received heading?
set heading new heading
Also I need to reverse this heading, so that the turtle receiving the heading does not travel at this heading, but rather travels in the opposite direction i.e the direction the other turtle was travelling from
ask turtles in-radius 5 [
set heading [ heading ] of myself
]
myself, aka the worst named primitive in NetLogo, refers to the turtle doing the asking.