Fog/Shroud Radius

I'm using the code below to create Fog of War/Shroud for an rts.

It waits for the friendly unit to actually be in the new grid unit before it shows enemy units.

Is there a way I could use the entities radius to allow visibility to multiple grid units?

;the Psuedo Grid (500,500) is equal to real world 0,0
;VALUES if =0 then invisable area, =1 then visbale
Dim mapgrid(1000,1000)
;This is how large each grid square will be in real XZ world values, play with this to see how it works
Global gridindex=20

;tree type
Type tree
Field entity
Field woodleft
Field Visable
End Type


;all units have these properties
Type Unit
Field Friendly
Field Visable
Field Entity
End Type



Graphics3D 640,480

;create friendly unit
U.unit=New unit
u\friendly=True
u\visable=True
u\entity=CreateCube()
EntityColor u\entity,0,0,200
PositionEntity u\entity,Rand(-20,20),0,Rand(-20,20)

;create a few enemies
For i=1 To 5
U.unit=New unit
u\friendly=False
u\visable=False
u\entity=CreateCube()
EntityColor u\entity,200,0,0
PositionEntity u\entity,Rand(-35,35),0,Rand(-35,35)
Next



;put some ground underneath it all
ground=CreatePlane()
EntityColor ground,0,100,0


For I=1 To 100
t.tree=New tree
T\entity=CreateCone()
PositionEntity t\entity,Rand(-100,100),0,Rand(-100,100)
EntityAlpha t\entity,.2
EntityColor t\entity,0,200,0
ScaleEntity t\entity,4,4,4
Next

;our camera
camera=CreateCamera()
temp=CreatePivot()
PositionEntity camera,10,40,40
PointEntity camera,temp
FreeEntity temp
CameraFogMode camera,1
CameraFogColor camera,100,100,100
CameraFogRange camera,25,190

;main loop
While Not KeyDown(1)
For u.unit=Each unit
checkgridarea(u)
;if unit is friendly we change grid he is in to
;visable, if unit is enemy we just check to see if he is
;inside of a visable area or invisable area, in in visable
;we change his alpha and visable state.
If u\friendly=True Then
MoveEntity u\entity,0,0,.1
TurnEntity u\entity,0,-.35,0
Else
MoveEntity u\entity,0,0,-.1
TurnEntity u\entity,0,.35,0
EndIf
Next
RenderWorld()
UpdateWorld()
Flip
Wend


Function CheckGridArea(cu.unit)
entity=cu\entity
Px=EntityX(entity,1)
Pz=EntityZ(entity,1)
gridX=Int((px/gridindex))+500
gridZ=Int((pz/gridindex))+500
If cu\friendly=True Then
If MapGrid(Gridx,Gridz)=0 Then
mapgrid(gridx,gridz)=1
;tree check not neccessary in a rts game as
;you cn usually see the terrain. You could get
;by with only unit checks. wich are fast.
For t.tree=Each tree
If t\visable=0 Then
If EntityDistance(t\entity,entity)<=GridIndex Then
t\visable=1
EntityAlpha t\entity,1
EndIf
EndIf
Next
EndIf
Else
;enemy/unfriendly unit check.. does not reveal map
;only reveals unit if map area is already explored
If mapgrid(gridx,gridz)=1 Then
cu\visable=1
EntityAlpha cu\entity,1
Else
cu\visable=0
EntityAlpha cu\entity,.1
EndIf
EndIf
End Function