TheGameCreators - CodeBase - Using Hermite Splines

Category: 3D Maths

Version: 1.0

Information

Uploaded: 12th May 2004 14:13

Modified: 1st Jan 1970 01:00

Author: Hamish McHaggis

Summary

This is a demontration of how to use vector2 commands to create a smooth curve between 2D points, using hermite splines.

Full Description

This is a demontration of how to use vector2 commands to create a smooth curve between 2D points, using hermite splines. Hermite splines use 4 control points, but by stringing lots together you can get a long smooth curve between points.<br /> <br /> The same can be done with vector3, just use 3D coords not 2D ones.

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

`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

`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

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

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Author Name:	Hamish McHaggis
CodeBase Entries:	14

CodeBase - Using Hermite Splines

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