Need code for an object swinging on a line

Blitz3D Forums/Blitz3D Programming/Need code for an object swinging on a line

3DFish (Posted 2005) [#1]

Hey guys Do any of you have some code for an object hanging on a piece of line and swinging sideways and in circles. I need this for my next project Adventure fishing 3. A fly fishing game. Thanks 3DFish

jhocking (Posted 2005) [#2]

On the one hand, that's a pretty vague request. Normally I would ask for clarification on exactly what you want. On the other hand, the fact that this is for a fishing game makes me assume the object is a fish pulling on the line and jerking around. This isn't necessarily an ideal approach, but a simple trick would be to create a pivot at the end of the pole (ie. where the line is coming from) and parent the fish to that pivot. Now if you rotate the pivot, the fish will be orbiting around that point.

WolRon (Posted 2005) [#3]

Verlet constraints?

3DFish (Posted 2005) [#4]

Thanks The line is fly line hanging from the tip of a fly rod. A fly will be attached to the end of the line. I need a swinging effect (the fly). My sin,cos,tan maths are a bit on the shaky side.

jhocking (Posted 2005) [#5]

"swinging" is actually the part I wanted clarification on. Are you talking about the movement of the fly during casting?

3DFish (Posted 2005) [#6]

no, only the movement of the fly when holding the rod before a cast.

Jeppe Nielsen (Posted 2005) [#7]

Just something I just coded :-) Try to catch the box with the rod. Graphics 800,600,16,2 SetBuffer BackBuffer() num=25 l#=200 dl#=l/num x#=400 For n=1 To num If n=1 startpoint.point=pointnew(x,100,True) p1.point=startpoint Else If n=num endpoint.point=pointnew(x,100,False,5) p1.point=endpoint Else p1.point=pointnew(x,100) EndIf contraintnew p1,p2.point EndIf p2.point=p1 x#=x#+dl Next p1.point=PointNew(200-25,100) p2.point=PointNew(250-25,100) p3.point=PointNew(250-25,150) p4.point=PointNew(200-25,150) boxhandle.point=pointnew(225-25,75,False,5) ContraintNew p1,p2 ContraintNew p2,p3 ContraintNew p3,p4 ContraintNew p4,p1 ContraintNew p1,p3 ContraintNew p2,p4 ContraintNew p1,boxhandle ContraintNew p2,boxhandle rodx=400 rody=300 Repeat Cls If pick=0 Text 400,20,"Catch the box with the fising rod",1 Else Text 400,20,"Box caught",1 Text 400,40,"Press mouse button to release box",1 EndIf PointUpdate ContraintUpdate mdx=(MouseX()-rodx) mdy=(MouseY()-rody) angle=ATan2(mdy,mdx) px=rodx+Cos(angle)*200 py=rody+Sin(angle)*200 Line rodx,rody,px,py PointMove startpoint,px,py Select pick Case 0 dx#=endpoint\x-boxhandle\x dy#=endpoint\y-boxhandle\y If Sqr(dx*dx+dy*dy)<8 boxcontraint.contraint=contraintnew( endpoint,boxhandle) pick=1 EndIf Case 1 If MouseDown(1) Delete boxcontraint pick=2 EndIf Case 2 dx#=endpoint\x-boxhandle\x dy#=endpoint\y-boxhandle\y If Sqr(dx*dx+dy*dy)>16 pick=0 EndIf End Select PointDraw ContraintDraw Flip Until KeyDown(1) End Type point Field x#,y# Field vx#,vy# Field lock Field size End Type Function PointNew.point(x#,y#,lock=False,size=0) p.point=New point PointMove(p,x#,y#) p\lock=lock p\size=size Return p End Function Function PointMove(p.point,x#,y#) p\x=x p\y=y End Function Function PointDraw() For p.point=Each point If p\size>0 Oval p\x-p\size,p\y-p\size,p\size+p\size,p\size+p\size,True EndIf Next End Function Function PointUpdate(dt#=0.1,gravity#=5) For p.point=Each point p\vy=p\vy+gravity*dt p\vx=p\vx*0.975 ;-Sgn(p\vx)*0.5*dt p\vy=p\vy*0.975 ;-Sgn(p\vy)*0.5*dt If p\lock=True p\vx=0 p\vy=0 EndIf p\x=p\x+p\vx*dt p\y=p\y+p\vy*dt If p\y>GraphicsHeight() p\vy=-p\vy*0.5 p\y=GraphicsHeight() EndIf Next End Function Function PointForce(p.point,fx#,fy#) p\vx=p\vx+fx p\vy=p\vy+fy End Function Type contraint Field s.point Field e.point Field l# ;relax length of contraint Field stiffness# ; stiffness of contraint Field damping# ; damping of contraint End Type Function ContraintNew.contraint(s.point,e.point,stiffness#=18,damping#=20) c.contraint=New contraint c\s=s c\e=e dx#=(c\e\x-c\s\x) dy#=(c\e\y-c\s\y) c\l=Sqr(dx*dx+dy*dy) c\stiffness#=stiffness# c\damping#=damping# Return c End Function Function ContraintUpdate(dt#=0.01,iterations=50) For i=1 To iterations For c.contraint=Each contraint dx#=(c\e\x-c\s\x) dy#=(c\e\y-c\s\y) currentlength#=Sqr(dx*dx+dy*dy) displacement#=currentlength-c\l nx#=dx#/currentlength# ny#=dy#/currentlength# fx#=nx#*(displacement*c\stiffness) fy#=ny#*(displacement*c\stiffness) fz#=nz#*(displacement*c\stiffness) fx#=fx#+nx#*c\damping# fy#=fy#+ny#*c\damping# PointForce c\s,fx*0.5*dt,fy*0.5*dt PointForce c\e,-fx*0.5*dt,-fy*0.5*dt Next Next End Function Function ContraintDraw() For c.contraint=Each contraint Line c\s\x,c\s\y,c\e\x,c\e\y Next End Function

3DFish (Posted 2005) [#8]

Wow Jeppe! That's really neat.. I'm looking for something similar, only in 3D. A rod tip (pivot). More line pivots hanging from the rod tip. Each line pivot should affect the other. The line pivots should only start moving when the rod tip moves. The line pivots needs to swing in the direction in which the rod tip moves.

KuRiX (Posted 2005) [#9]

Wow! Really impressive piece of code, i like it! congratulations!

IPete2 (Posted 2005) [#10]

Wow! Fab stuff, thanks for sharing that! IPete2.

3DFish (Posted 2005) [#11]

Thanks for all the input guys. I have found a solution. Check out this thread by Mr. Picklesworth http://www.blitzbasic.com/Community/posts.php?topic=39525&hl=rope