NavMeshesCMSC425.01Spring2019

Stillattables…

Administrivia

• Hw2posted

• Project2outlineready,fulldescriptionsoon

• Practiceexamslinked

• Anychoicesonwhatwedoafterbreak?• Gamedesignbigsubject,lotsoftopicswecanchoosefrom

Project2:CrabSoup,Anyone?

• Goal:Playermustretrievetreasurefromchestonfarisland• Problem:MutatedCrabswillattack

Project2:CrabSoup,Anyone?

• Goal:Playermustretrievetreasurefromchestonfarisland• Problem:MutatedCrabswillattack

• NewUnityelements:• Terrain• NavMesh• AnimatedfiguresforPlayerandCrabs

Yourinstructorplays…

Details

• Part1:Makeittothetreasure!MakeaterrainwithaNavMesh,navigatetotheTreasure,andhavetheCrabschase.Playerhumanoid,Crabsblocks.Winifyoumakeittothetreasurewithoutbeing“crabbed”

• Part2:AnimatePlayerandCrabswithMixamo animations.Addakeythatmustbefoundtoopenchest,returntodocktowin.AddUIgraphictoshowthatkeyispickedup.

• Reach?:Makeitunderwaterwithswimminganimation• Freeto:addelementstomakeitmoreplayable,changethemeifspiritiskept

Today’squestion

HowNPCsmovearound:NavMeshes

Navigationproblems• Navigatingfromplacetoplace• Densecrowdnavigation• Coordinatedteammovement• Pursuit• Movingcomplex/articulatedshape

• Pianomoversproblem(rigid)• Skeleton(articulated)

@UMD:DineshandMing

• Densecrowdsimulations• Howtomovemanyagentsnaturally

• Video

NavigationVersion1:UseamapCreategraphstructureUseDijkstra'salgorithm

Shortestpath

Assumption:Worldisrigid,limitedlanesformovement

Whatis"shortest"path?

• Distance?

Whatis"shortest"path?

• Distance?• Speed?• Energycost?• Exposuretoenemy?

• Hexmap• 6directions• Terraintypes=>speedcosts

NavigationVersion2:OpenTerrain

• Mixofobstaclesandopenspaces:"freespacegeometry"• Moreoptionsfordirection• Howpickpath?

Howpickbestpath?

• Shortestmaynotbemostnatural(dashedline)• Needwaytodetectnaturalcorridors

Solution1:Waypointroadmap

• Preprocessspaceintographofwaypoints• Placewaypointsalongnaturalcorridors

Solution1:Waypointroadmap

• Preprocessspaceintographofwaypoints• Placewaypointsalongnaturalcorridors• Drawbacks• Couldneedlotsofwaypoints• Hardertoplanforcoordinatedteammovement

Solution2:Navmesh

• Preprocessspaceintomeshoffreeareasaspolygons• Planmovementbetweenpolygons• Betweenedges• Betweencenters

• Multiplelevelgraphsearch• Firstbetweenregions• Thenpickentryandexitpoints

Navmeshes canbe

• Labeledwithdifferentterraintypes• Setwith"gates"

• 2Dmanifoldswhicharetopologicallycomplex(eg,non-planar)

UsingNavmesh

• Insideregionusedirectpath

• Regions(andsubregions)canbelabeledwithdifferentterraintypesandcosts

CreatingNavmeshes fromterrain

• Step1:Findwalkablesurfaces• Aslargepolygon"map"

• Step2:Simplifyboundaries• Simplifypolygon"map"

• Step3:Triangulate"map"• Coverwithsetoftriangles

CreatingNavmeshes fromterrain

• Step1:Findwalkablesurfacesbasedonagentheight,width,slopeability

• Variationonpianomoversproblem

(a) (b)

h

too shortok

too steep

CreatingNavmeshes fromterrain

• Step2:Simplifyboundaries• Simplifypolygon"map"

• Recursiverefinementofstraightline

CreatingNavmeshes fromterrain

• Step3:Triangulate"map"• Coverwithsetoftriangles

• Bridgeholes• Cutears(!)

(a) (b)

v0

v1v2

vi�1

vi+1

viear

(c)

vn

chord

chordbridging

UseNavmesh:findpath

• Discretizebyaddingpoints• Findshortestpath

(b) (c)(a)

UseNavmesh:refine

• Smoothandcleanpath

(a) (b) (c)

t

s

t

s

t

s

Navmeshes inUnity

• Createterrain• Terraineditor

• Setagentnavigationproperties• Height,widthofagent• Slopecapability

• BakeNavmesh• Findsnavigableregions• Createsmesh

Agentproperties

• Radius,Height• Stepheight• Maxslope

• Canhavemultipleagenttypes

Offmeshlinks

Question

• Howdoesthisallrelatetocolliders?

Readings

• LookatUnitymanualandtutorials• Terrain• https://docs.unity3d.com/Manual/terrain-UsingTerrains.html

• NavMesh• https://unity3d.com/learn/tutorials/topics/navigation/navmesh-agent• https://docs.unity3d.com/Manual/nav-BuildingNavMesh.html

• Animation• https://unity3d.com/learn/tutorials/topics/animation/animate-anything-mecanim• https://unity3d.com/learn/tutorials/s/animation