TheDarthster asked about hermite splines the other day and so I decided to figure out how to use them, and see if they were of any use. Turns out they are potentially a lot more useful than catmull rom splines, as you can control the tangent and speed of the curve through the control points. You can see from the screen anyway
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`2D Hermite Splines in DBPro
`By Joseph Thomson
`12/05/04
randomize timer()
set display mode 800,600,32
type pointType
x as integer
y as integer
cx as integer
cy as integer
cmx as integer
cmy as integer
endtype
`Maximum number of points
maxPoints as integer = 100
dim points(maxPoints) as pointType
`Number of starting points (has to be at least 2)
numPoints as integer = 2
`Number of points between main points (displaying the curve)
numSections as integer = 50
pointSelected as integer
controlPointSelected as integer
controlPointMirrorSelected as integer
mouseHold as integer
spaceHold as integer
controlScale as float = 4.0
`Randomize the starting points coordinates and the control point coordinates
for x = 1 to 2
points(x).x = rnd(600)+100
points(x).y = rnd(400)+100
points(x).cx = rnd(100)-50
points(x).cy = rnd(100)-50
points(x).cmx = -points(x).cx
points(x).cmy = -points(x).cy
next x
`Create the vectors 1 to 5
tmp = make vector2(1)
tmp = make vector2(2)
tmp = make vector2(3)
tmp = make vector2(4)
tmp = make vector2(5)
sync on
sync rate 0
do
`User can control control scale
if upkey() = 1
inc controlScale,0.01
endif
if downkey() = 1
dec controlScale,0.01
endif
`Control addition of points
if mouseclick() = 2
if numPoints < maxPoints and mouseHold = 0
inc numPoints
points(numPoints).x = mousex()
points(numPoints).y = mousey()
points(numPoints).cx = rnd(100)-50
points(numPoints).cy = rnd(100)-50
points(numPoints).cmx = -points(numPoints).cx
points(numPoints).cmy = -points(numPoints).cy
endif
mouseHold = 1
endif
`Control deletion of points
if spacekey() = 1
if numPoints > 2 and spaceHold = 0
dec numPoints
endif
spaceHold = 1
else
spaceHold = 0
endif
mouseHoldSwitch = 0
`Loop through all points
for x = 1 to numPoints
`Control moving of points
if mouseclick() = 1
if mousex() >= points(x).x-3 and mousex() <= points(x).x+3 and mousey() >= points(x).y-3 and mousey() <= points(x).y+3 and mouseHold = 0
pointSelected = x
else
if mousex() >= points(x).x+points(x).cx-3 and mousex() <= points(x).x+points(x).cx+3 and mousey() >= points(x).y+points(x).cy-3 and mousey() <= points(x).y+points(x).cy+3 and mouseHold = 0
controlPointSelected = x
else
if mousex() >= points(x).x+points(x).cmx-3 and mousex() <= points(x).x+points(x).cmx+3 and mousey() >= points(x).y+points(x).cmy-3 and mousey() <= points(x).y+points(x).cmy+3 and mouseHold = 0
controlPointMirrorSelected = x
endif
endif
endif
mouseHoldSwitch = 1
endif
`Draw lines between the points
ink rgb(100,100,255),0
line points(x).x+points(x).cx,points(x).y+points(x).cy,points(x).x+points(x).cmx,points(x).y+points(x).cmy
`Draw point
ink rgb(255,255,0),0
box points(x).x-2,points(x).y-2,points(x).x+2,points(x).y+2
`Draw control point
ink rgb(0,0,255),0
box points(x).x+points(x).cx-2,points(x).y+points(x).cy-2,points(x).x+points(x).cx+2,points(x).y+points(x).cy+2
`Draw control point mirror
ink rgb(0,0,255),0
box points(x).x+points(x).cmx-2,points(x).y+points(x).cmy-2,points(x).x+points(x).cmx+2,points(x).y+points(x).cmy+2
next x
`Mouse hold for one click only
if mouseHoldSwitch = 1
mouseHold = 1
endif
`Move selected point if there is one
if pointSelected <> 0
points(pointSelected).x = mousex()
points(pointSelected).y = mousey()
endif
`Move selected control point if there is one
if controlPointSelected <> 0
points(controlPointSelected).cx = mousex()-points(controlPointSelected).x
points(controlPointSelected).cy = mousey()-points(controlPointSelected).y
points(controlPointSelected).cmx = -points(controlPointSelected).cx
points(controlPointSelected).cmy = -points(controlPointSelected).cy
endif
`Move selected control point mirror if there is one
if controlPointMirrorSelected <> 0
points(controlPointMirrorSelected).cmx = mousex()-points(controlPointMirrorSelected).x
points(controlPointMirrorSelected).cmy = mousey()-points(controlPointMirrorSelected).y
points(controlPointMirrorSelected).cx = -points(controlPointMirrorSelected).cmx
points(controlPointMirrorSelected).cy = -points(controlPointMirrorSelected).cmy
endif
ink rgb(255,255,255),0
`Loop through all active points
for x = 2 to numPoints
`Fill vectors with point coordinates
set vector2 1,points(x-1).x,points(x-1).y
set vector2 2,points(x-1).cx*controlScale,points(x-1).cy*controlScale
set vector2 3,points(x).x,points(x).y
set vector2 4,points(x).cx*controlScale,points(x).cy*controlScale
`Loop through the sections between points
for y = 1 to numSections-1
`Work out point on hermite spline (filledVector,pointA,pointB,pointC,pointD,value (0.0 = beginning of curve, 1.0 = end of curve, 0.5 = half way down curve))
`pointA = start of the curve, pointB = tangent of the curve at pointA (also has a distance), pointC = end of the curve, pointD = tangent of the curve at pointC (also has a distance)
hermite vector2 5,1,2,3,4,1.0/numSections*y
`Draw point
dot x vector2(5),y vector2(5)
next y
next x
`Reset one click variable and point selected if no mouse is clicked
if mouseclick() = 0
mouseHold = 0
pointSelected = 0
controlPointSelected = 0
controlPointMirrorSelected = 0
endif
`Info
ink rgb(255,255,255),0
text 10,10,"2D Hermite Splines"
text 10,25,"By Joseph Thomson 12/05/04"
text 10,45,"LMB to move points"
text 10,60,"RMB to add a point"
text 10,75,"Space bar to delete the last point"
text 10,90,"Up and down to change the control scale: "+str$(controlScale)
sync
cls
loop
Athelon XP 1600+/Radeon 9600 Pro/256 RAM
