Homekeeping

This code has been declared by its author to be Public Domain code.

Homekeeping by Krischan

2009

Moving a player mesh far away from 0,0,0 results in mesh jitter due inaccuracy of vertex float positions (or even "jumping" meshes). If you want to use very large distances like in a space game (>100.000), the homekeeping function is the answer. It just moves the player mesh in a given distance (ex. 1000 Units) and puts it back to the opposite position while moving the world instead of the player. The world must be attached to a "masterpivot", even collisions work this way.

Here is a demo, homekeeping is disabled by default to show the jitter effect first. To enable homekeeping just uncomment this line in the main loop:

;HomeKeeping(player,masterpivot,1000)

Moving with mouse/arrow keys, SPACE=wireframe, LMB=Zoom 10x, RMB=Move 10x faster

demo.bb

Graphics3D 800,600,32,2

Include "homekeeping.bb"

Global GameSpeed%=60
Global Screenwidth%=GraphicsWidth()
Global Screenheight%=GraphicsHeight()
Global FramePeriod%=1000/GameSpeed
Global FrameTime%=MilliSecs()-FramePeriod

Global movetarget%,masterpivot%
Global player%,cam%,ship%,sun%,light%
Global iwc%,ihc%,iwk%,ihk%
Global kreuz%,cursor%

Global distance#=9000.0
Global rollspeed#=1.0
Global turnspeed#=2.0
Global maxroll#=20.0
Global speed#=100.0

Global wf%,mx%,my%,t1#,t2#,roll#,currentspeed#

InitWorld()

MoveMouse Screenwidth/2,Screenheight/2

While Not KeyHit(1)
	
	Local FrameElapsed%,FrameTicks%,FrameTween#,t%
	
	Repeat FrameElapsed=MilliSecs()-FrameTime Until FrameElapsed
	FrameTicks=FrameElapsed/FramePeriod
	FrameTween=Float(FrameElapsed Mod FramePeriod)/Float(FramePeriod)
	
	For t=1 To FrameTicks
		
		FrameTime=FrameTime+FramePeriod : If t=FrameTicks Then CaptureWorld
		
		Movement()
		
		localx=EntityX(player)
		localy=EntityY(player)
		localz=EntityZ(player)
		
        ;HomeKeeping(player,masterpivot,1000)
		
		UpdateWorld
		
	Next
	
	RenderWorld FrameTween
	
	CameraProject cam,EntityX(movetarget,1),EntityY(movetarget,1),EntityZ(movetarget,1)
	DrawImage kreuz,ProjectedX()-iwk,ProjectedY()-ihk
	DrawImage cursor,mx-iwc,my-ihc
	
	Text 0, 0,"Local Position....: "+localx+" | "+localy+" | "+localz
	Text 0,15,"Global Position...: "+globalx+" | "+globaly+" | "+globalz
	Text 0,30,"Simulated Position: "+(globalx+localx)+" | "+(globaly+localy)+" | "+(globalz+localz)
	Text 0,45,"Distance to Sun...: "+EntityDistance(player,sun)
	
	Flip 0
	
Wend

End


Function InitWorld()
	
	Local mesh%,surf%,cube%,i%,s#,d#
	
	masterpivot=CreatePivot()
	
	player=CreatePivot()
	PositionEntity player,0,1000,-10000
	
	ship=CreateCube(player)
	EntityFX ship,1
	EntityColor ship,0,128,255
	ScaleEntity ship,1,0.05,1
	PositionEntity ship,0,-0.5,1.5
	EntityOrder ship,-1000
	
	movetarget=CreatePivot(player)
	MoveEntity movetarget,0,0,distance
	
	cam=CreateCamera(player)
	PositionEntity cam,0,0.5,-1.5
	CameraFogMode cam,True
	CameraRange cam,1,1000000
	CameraFogRange cam,500000,1000000
	CameraZoom cam,1
	CameraClsColor cam,0,0,0
	CameraFogColor cam,0,0,0
	
	cursor=CreateImage(33,33)
	Color 255,0,0
	SetBuffer ImageBuffer(cursor)
	Rect 0,0,33,33,0
	iwc=ImageWidth(cursor)/2
	ihc=ImageHeight(cursor)/2
	
	kreuz=CreateImage(33,33)
	Color 0,255,0
	SetBuffer ImageBuffer(kreuz)
	Line 16,0,16,33
	Line 0,16,33,16
	iwk=ImageWidth(kreuz)/2
	ihk=ImageHeight(kreuz)/2
	
	SetBuffer BackBuffer()
	
	mesh=CreateMesh(masterpivot)
	surf=CreateSurface(mesh)
	EntityFX mesh,2
	
	sun=CreateSphere(32,masterpivot)
	EntityFX sun,1+8
	EntityColor sun,255,255,224
	ScaleMesh sun,6000,6000,6000
	
	light=CreateLight(2,masterpivot)
	LightRange light,50000
	AmbientLight 32,32,32
	
	cube=CreateCube()
	
	For i=1 To 25000
		
		s#=Rnd(10,100)
		If Rnd(1)>0.999 Then s=Rnd(100,1000)
		d#=Rnd(10000,100000)
		ScaleEntity cube,s,s,s
		PositionEntity cube,0,0,0
		
		RotateEntity cube,0,0,0
		TurnEntity cube,Rnd(-Rnd(0,90),Rnd(0,90)),Rnd(0,360),0
		MoveEntity cube,0,0,d
		PointEntity cube,sun
		
		AddToMesh(cube,mesh,128,128,128,1)
		
	Next
	
	FreeEntity cube
	
	UpdateNormals mesh
	
	PointEntity player,sun
	
End Function


Function Normalize#(value#=128.0,value_min#=0.0,value_max#=255.0,norm_min#=0.0,norm_max#=1.0)
	
	Return ((value-value_min)/(value_max-value_min))*(norm_max-norm_min)+norm_min
	
End Function


Function Movement()
	
	Local multi#,limit#
	
	roll=0
	
	If KeyDown(203) Then roll=rollspeed
	If KeyDown(205) Then roll=-rollspeed
	If KeyHit(57) Then wf=1-wf : WireFrame wf
	
	If MouseDown(1) Then CameraZoom cam,10 : limit=0.1 Else CameraZoom cam,1 : limit=1.0
	If MouseDown(2) Then multi=10 Else multi=1
	
	currentspeed=(KeyDown(200)-KeyDown(208))*speed*multi
	
	MoveEntity player,0,0,currentspeed
	
	mx=MouseX()
	my=MouseY()
	
	t1=Normalize(my,0,Screenheight,-1,1)
	t2=Normalize(mx,0,Screenwidth,1,-1)
	
	RotateEntity ship,t1*maxroll,t2*maxroll,t2*maxroll*2
	TurnEntity player,t1*turnspeed*limit,t2*turnspeed*limit,roll*turnspeed
	
End Function


Function AddToMesh(source%,target%,r%,g%,b%,a#)
	
	Local vert%[2],vr%[2],vg%[2],vb%[2],va#[2]
	Local oldvert%,i1%,i2%,v1%,v2%
	Local surf%,surf1%=GetSurface(source,1),surf2%
	
	v1=CountVertices(surf1)
	For v2=1 To CountSurfaces(target)
		
		surf=GetSurface(target,v2)
		If CountVertices(surf)+v1<64000 Then surf2=surf : Goto skip
		
	Next
	
	surf2=CreateSurface(target)
	
	.skip
	
	For i1=0 To CountTriangles(surf1)-1
		
		For i2=0 To 2
			
			oldvert = TriangleVertex(surf1,i1,i2)
			
			vr[i2]=r
			vg[i2]=g
			vb[i2]=b
			va[i2]=a
			
			TFormPoint VertexX(surf1,oldvert),VertexY(surf1,oldvert),VertexZ(surf1,oldvert),source,target
			vert[i2]=AddVertex(surf2,TFormedX(),TFormedY(),TFormedZ(),VertexU(surf1,oldvert),VertexV(surf1,oldvert))
			VertexColor surf2,vert[i2],r,g,b,a
			VertexNormal surf2,vert[i2],VertexNX(surf1,oldvert),VertexNY(surf1,oldvert),VertexNZ(surf1,oldvert)
			
		Next
		
		AddTriangle(surf2,vert[0],vert[1],vert[2])
		
	Next
	
End Function

Global localx#,localy#,localz#
Global globalx#,globaly#,globalz#
Global simx#,simy#,simz#

; keeps the player in a given distance while the world can move far away
Function HomeKeeping(player%,world%,homesize%=100)
	
	; store local player position
	localx=EntityX(player)
	localy=EntityY(player)
	localz=EntityZ(player)
	
	; check X axis
	While localx>homesize
		globalx=globalx+homesize
		localx=localx-homesize
		PositionEntity player,localx,localy,localz
		MoveEntity world,-homesize,0,0
	Wend
	While localx<-homesize
		globalx=globalx-homesize
		localx=localx+homesize
		PositionEntity player,localx,localy,localz
		MoveEntity world,homesize,0,0
	Wend
	
	; check Y axis
	While localy>homesize
		globaly=globaly+homesize
		localy=localy-homesize
		PositionEntity player,localx,localy,localz
		MoveEntity world,0,-homesize,0
	Wend
	While localy<-homesize
		globaly=globaly-homesize
		localy=localy+homesize
		PositionEntity player,localx,localy,localz
		MoveEntity world,0,homesize,0
	Wend
	
	; check Z axis
	While localz>homesize
		globalz=globalz+homesize
		localz=localz-homesize
		PositionEntity player,localx,localy,localz
		MoveEntity world,0,0,-homesize
	Wend
	While localz<-homesize
		globalz=globalz-homesize
		localz=localz+homesize
		PositionEntity player,localx,localy,localz
		MoveEntity world,0,0,homesize
	Wend
	
	; store simulated player position
	simx=localx+globalx
	simy=localy+globaly
	simz=localz+globalz
	
End Function

Comments

Oiduts Studios

2009

This may come in handy, Thanks!

RemiD

2014

I have done something similar but in a zone of 100x100x100units.
The next step is to find a way to save then delete then load then create the environment and entities in real time, without causing slowdown...

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