This example shows how you can create a continuous bezier spline using multiple bsplines
Hope it of some use :)
;**************************************************
;* Continuous Bezier Spline by Jeppe Nielsen 2003 *
;**************************************************
;* Email: nielsen_jeppe@... *
;**************************************************
;* Based on Wedoe´s bezier function *
;**************************************************
Global beziercontrolpoint
Graphics 800,600,16,2
SetBuffer BackBuffer()
beziernew(300,400,325,400,400,400,375,400)
bezier.bezier=Null
event=0
smooth#=0.01
Repeat
Cls
Text 400,0,"Continuous Bezier Spline by Jeppe Nielsen",1
Text 400,20,"Left mouse button to drag control points",1
Text 400,40,"Right mouse button to create a new bezier piece",1
Text 400,60,"+/- to control curve smoothness : " +smooth#,1,0
If MouseDown(1)
Select event
Case 0
bezier=bezierselect.bezier(MouseX(),MouseY())
If bezier<>Null
event=1
EndIf
Case 1
beziermovepoint(bezier,beziercontrolpoint,MouseX(),MouseY())
End Select
Else
event=0
EndIf
;new bezier
If MouseHit(2)
lb.bezier=Last bezier
;last bezier´s end point
x=lb\x[1]
y=lb\z[1]
beziernew(x,y,x+25,y,x+100,y,x+75,y)
EndIf
If KeyDown(74)
smooth#=smooth#+0.01
If smooth#>1
smooth#=1
EndIf
EndIf
If KeyDown(78)
smooth#=smooth#-0.01
If smooth#<0.001
smooth#=0.001
EndIf
EndIf
bezierdraw(smooth#)
Flip
Until KeyDown(1)
End
;x,y,z[0..1] = End points
;x,y,z[2..3] = Control points
Type bezier
Field x#[3],z#[3]
Field b.bezier ;before
Field a.bezier ;after
Field length#
End Type
Function beziernew.bezier(x1#,z1#,vx1#,vz1#,x2#,z2#,vx2#,vz2#)
b.bezier=New bezier
b\x[0]=x1
b\z[0]=z1
b\x[1]=x2
b\z[1]=z2
b\x[2]=vx1
b\z[2]=vz1
b\x[3]=vx2
b\z[3]=vz2
bezierconnect()
Return b
End Function
Function bezierdelete(b.bezier)
Delete b
End Function
Function bezierdeleteall()
For b.bezier=Each bezier
bezierdelete(b)
Next
End Function
Function beziermovepoint(b.bezier,point,x#,z#)
b\x#[point]=x#
b\z#[point]=z#
Select point
Case 0
If b\b<>Null
dx#=(b\x[0]-b\x[2])
dz#=(b\z[0]-b\z[2])
b\b\x#[3]=b\x[0]+dx#
b\b\z#[3]=b\z[0]+dz#
EndIf
End Select
If b\b<>Null
Select point
Case 0
b\b\x#[1]=x#
b\b\z#[1]=z#
dx#=(b\x[0]-b\x[2])
dz#=(b\z[0]-b\z[2])
b\b\x#[3]=b\x[0]+dx#
b\b\z#[3]=b\z[0]+dz#
Case 2
dx#=(b\x[0]-b\x[2])
dz#=(b\z[0]-b\z[2])
b\b\x#[3]=b\x[0]+dx#
b\b\z#[3]=b\z[0]+dz#
End Select
EndIf
If b\a<>Null
Select point
Case 1
b\a\x#[0]=x#
b\a\z#[0]=z#
dx#=(b\x[1]-b\x[3])
dz#=(b\z[1]-b\z[3])
b\a\x#[2]=b\x[1]+dx#
b\a\z#[2]=b\z[1]+dz#
Case 3
dx#=(b\x[1]-b\x[3])
dz#=(b\z[1]-b\z[3])
b\a\x#[2]=b\x[1]+dx#
b\a\z#[2]=b\z[1]+dz#
End Select
EndIf
End Function
Function bezierconnect()
For b.bezier=Each bezier
b\a=Null
b\b=Null
For bb.bezier=Each bezier
If b<>bb
dx#=(bb\x[0]-b\x[1])
dz#=(bb\z[0]-b\z[1])
dist#=dx*dx+dz*dz
If dist<16
b\a=bb
EndIf
dx#=(bb\x[1]-b\x[0])
dz#=(bb\z[1]-b\z[0])
dist#=dx*dx+dz*dz
If dist<16
b\b=bb
EndIf
EndIf
Next
Next
End Function
Function bezierselect.bezier(x,y)
For b.bezier=Each bezier
For n=0 To 3
Oval b\x[n]-4,b\z[n]-4,8,8
If x>b\x[n]-4
If y>b\z[n]-4
If x<b\x[n]+4
If y<b\z[n]+4
beziercontrolpoint=n
Return b
EndIf
EndIf
EndIf
EndIf
Next
Next
End Function
Function bezierdraw(inc#=0.01)
b.bezier=First bezier
t#=0
pointx# = b\x[0]*(1-t)^3 + 3*b\x[2]*(1-t)^2*t + 3*b\x[3]*(1-t)*t^2 + b\x[1]*t^3
pointz# = b\z[0]*(1-t)^3 + 3*b\z[2]*(1-t)^2*t + 3*b\z[3]*(1-t)*t^2 + b\z[1]*t^3
lpointx#=pointx#
lpointz#=pointz#
While b<>Null
t#=0
For n=0 To 3
Oval b\x[n]-4,b\z[n]-4,8,8
Next
While t#<=1
pointx# = b\x[0]*(1-t)^3 + 3*b\x[2]*(1-t)^2*t + 3*b\x[3]*(1-t)*t^2 + b\x[1]*t^3
pointz# = b\z[0]*(1-t)^3 + 3*b\z[2]*(1-t)^2*t + 3*b\z[3]*(1-t)*t^2 + b\z[1]*t^3
Line pointx,pointz,lpointx,lpointz
lpointx#=pointx#
lpointz#=pointz#
t#=t#+inc#
Wend
t#=1
pointx# = b\x[0]*(1-t)^3 + 3*b\x[2]*(1-t)^2*t + 3*b\x[3]*(1-t)*t^2 + b\x[1]*t^3
pointz# = b\z[0]*(1-t)^3 + 3*b\z[2]*(1-t)^2*t + 3*b\z[3]*(1-t)*t^2 + b\z[1]*t^3
Line pointx,pointz,lpointx,lpointz
b=After b
Wend
End Function
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