multi layered navmesh ictopen2011

7/24/2019 Multi Layered Navmesh ICTOPEN2011

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Multi-Layered NavigationMeshes

Wouter G. van Toll, Atlas F. Cook IV, oland GeraertsICT.OPEN 2011


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Motivation

!ath "lanning in ga#es andsi#ulations

$end virtual %hara%ters &ro# start to goal' in a s#oothan visually convincing way

such that they pay attention to other %hara%ters

in real-ti#e, even for large crowds

Ty"i%al solution( navigation #esh

Subdivision of the walkable spaceinto 2D "olygons

Allows sooth, !e"ible oveent

Shouldbe built auto#ati%ally


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esear%h is ne%essary)

I& you think "ath "lanning in ga#es is*solved+'


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What to do

Whats the "role# /u#an error

!oor data stru%tures

!oor algorith#s

What do 0e 0ant

A general &ra#e0ork, as auto#ati% as"ossile

1ur &ra#e0ork( "ath "lanning 0ith%orridors Autoatically built navigation esh

%lobal path planning

&ocal forces

1ur "a"er


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23 data stru%ture( The#edial a4is

The set o& all "oints 0ith at least t0o%losest osta%le "oints

*The #iddle+ o& the0alkale s"a%e

Ma4i#u# %learan%eto osta%les

!reserves %onne%tivity

A use&ul road#a" ()f there*s no path on

the edial a"is, thenthere*s no path at all+


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The 54"li%it Corridor Ma"65CM7

Annotated #edial a4is 6Geraerts,28987

All event points storea %losest osta%le "oint

on oth sides 54a%tsudivision o&

the 0alkale s"a%e

A navigation #esh O(n)storage

O(n logn)uild ti#e


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The 54"li%it Corridor Ma"65CM7 - 2

Features o& the 5CM Gloal "lanning

.n the A only0 ecient

3esult0 "ath4%orridor

Indi%ative oute Method 56araou7as et al, 299:;

$hort "aths 0ith %learan%e

Collision avoidan%e

Lo%al u"dates (A 3A ?12

5:%ient, ;e4ile "ath "lanning < %ro0d

si#ulation


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Multi-layered navigation

Cro0d si#ulation is o&ten a 23 "role# Many *=3+ environ#ents have a 23 to" vie0

(footprint)

>ut 0hat aout #ulti-layered

environ#ents Its not 23

Its not =3

Its a set o& %onne%ted 23 "role#s

54isting #ethods are approximating

=3 grid( loss o& "re%ision

1ur #ethod is exact


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This "a"er

We e4tend the 5CM to #ulti-layeredenviron#ents It is %onstru%ted auto#ati%ally

Assu#"tion( layers are given >an be e"tracted fro #D data

All 23 algorith#s 0ill still 0ork

3eal@tie crowd siulation in ulti@layered environents

e%all( The 5CM is an annotated #edial a4is 1ur algorith# ?rst uilds the multila!ere"

me"ial axis

$a#e annotations( multila!ere" EC#


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C01

Multi-layered( 3e?nitions

What is a #ulti-layered environ#ent A realisticset o& la!ersand connections

Layer $i >ounded "lanar area 0ith a "olygonal

&oot"rint 23

Conne%tion C%& Line seg#ent %onne%ting $%to $&

/al& osta%le in $%, hal& 0indo0 to $&6a%%ess

side7

Also a""ears in $&, 0ith ;i""ed sides

*ealisti%+

Layers are logi%ally %onne%ted

All &oot"rints are taken &ro# 9 to" vie0


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Co#"uting the M-L #ediala4is

Constru%tion algorith#9.>uild the 23 #edial a4is o& ea%h layer'

treating connections as ipassable obstacles

>orrect, e"cept inin;uen%e @ones ie the areas with an access sideas a closest

obstacle

hese ust be Blled in


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Co#"uting the M-L #ediala4is - 2

Constru%tion algorith#2.1"en u" the %onne%tions one y one

>hoose any connection, say C%&between layers LAand LB

Cind the %onne%tion s%ene'%&0 all obstacles adacent to

CAB

>opute the edial a"is of SAB

erge it with the edial a"esof LAand LB

reat LAand LB as one layer

fro now on

=. e"eat until all %onne%tions are o"en

esult(9 %ontinuous #edial a4is o& the 0hole

environ#ent$

%

$&

C%&


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Co#"uting the M-L #ediala4is - =

54a#"le Note( e4tra verti%es on layer transitions

Co#"le4ity

n Bosta%le verti%es B%onne%tions

$torage( 16n7 usually 16n7 worst@case

Constru%tion( 16nlog n7 usually 16nlog n7worst@case

Eorst case is very uncoon

In%re#ental a""roa%h handles every %ase)

Conne%tions #ay e %lose together

1rder o& o"ening does not #atter


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esult( Multi-layered 5CM

Add %losest-"oint annotations 5CM %o#"uted in DE ms

eal-ti#e #ulti-layered %ro0d si#ulation


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54"eri#ental results

Adding osta%les hardly ae%tsstit%hing ti#e

Conne%tion in;uen%e is usually lo%al

unning ti#e in%reases 0ithB%onne%tions

I#"rove#ents are "ossile

We %an steer very large %ro0ds inreal-ti#e

Tens o& thousands o& %hara%ters


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Con%lusion

1ur in%re#ental algorith#' uilds the #edial a4is o& a #ulti-layered

environ#ent

e4tends this to the #ulti-layered 54"li%itCorridor Ma"

1ur navigation #esh'

is uilt auto#ati%ally, given the se"aratelayers

is the ?rst e4a%t #esh &or "olygonal#ulti-layered environ#ents

su""orts e:%ient and ;e4ile %ro0dsi#ulation


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Future 0ork

What %an still e added Faster auto#ati% layer e4tra%tion

.ngoing Sc proects

1ther ga#e a%tions and environ#ents

Fuping, #D surfaces,

There 0ill al0ays e ne0 interesting

"role#s


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The 5nd

Thank you)

multi layered navmesh ictopen2011

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