# GLBasic forum

## Codesnippets => 2D-snippets => Topic started by: MrTAToad on 2009-Jan-21

Title: Moving between two sets of coordinates
This code allows you to calculate the X/Y step values between two sets of coordinates, allowing you to move between the two.

Code: (glbasic) [Select]
`// --------------------------------- //// Project: TestLineMove// Start: Monday, January 19, 2009// IDE Version: 6.138TYPE tMoveAlongLine ax ay ex ey bx by ix iy numSteps maxDistanceENDTYPEFUNCTION _dummy:ENDFUNCTIONINLINE #include "math.h" extern double atan2 (      double y,      double x );ENDINLINEFUNCTION setTo:x,y moveAlongLine.ax=x moveAlongLine.ay=yENDFUNCTIONFUNCTION changeTo:bx,by moveTo(moveAlongLine.ax,moveAlongLine.ay,bx,by)ENDFUNCTIONFUNCTION angleBetweenPoints:ax,ay,ex,eyINLINE double angle; angle=atan2(ex-ax,ey-ay); if (angle<0.0) { angle=180.0+(180.0+angle); } return angle;ENDINLINEENDFUNCTIONFUNCTION moveTo:sx,sy,fx,fy,mDistance=-1.0LOCAL dxLOCAL dy moveAlongLine.ax=sx moveAlongLine.ay=sy moveAlongLine.ex=fx moveAlongLine.ey=dy dx=fx-sx dy=fy-sy moveAlongLine.bx=ABS(dx) moveAlongLine.by=ABS(dy) IF moveAlongLine.bx>moveAlongLine.by moveAlongLine.numSteps=moveAlongLine.bx ELSE moveAlongLine.numSteps=moveAlongLine.by ENDIF moveAlongLine.maxDistance=mDistance moveAlongLine.ix=dx/moveAlongLine.numSteps moveAlongLine.iy=dy/moveAlongLine.numStepsENDFUNCTIONFUNCTION process%:speed IF moveAlongLine.numSteps<=0.0 RETURN FALSE ELSE INC moveAlongLine.ax,moveAlongLine.ix*speed INC moveAlongLine.ay,moveAlongLine.iy*speed DEC moveAlongLine.numSteps,speed IF moveAlongLine.maxDistance>0.0 DEC moveAlongLine.maxDistance,speed IF moveAlongLine.maxDistance<=0.0 moveAlongLine.numSteps=0.0 moveAlongLine.maxDistance=0.0 RETURN FALSE ENDIF ENDIF ENDIF RETURN TRUEENDFUNCTION`
The angle between two points code needs changing as its inaccurate, but the rest works fine.

The test code :

Code: (glbasic) [Select]
`GLOBAL moveAlongLine AS tMoveAlongLineSETSCREEN 1024,768,0moveTo(0,0,200,100)DEBUG "Angle : "+angleBetweenPoints(100,100,10,20)+"\n"WHILE TRUE DEBUG "X:"+moveAlongLine.ax+"\n" DEBUG "Y:"+moveAlongLine.ay+"\n" DEBUG moveAlongLine.numSteps+"\n" DRAWLINE moveAlongLine.ax,moveAlongLine.ay,1,1,RGB(255,255,255) SHOWSCREEN process(0.25)WEND`
If anyone has a better routine for calculating the angle between two coordinates, let me know :)
Title: Re: Moving between two sets of coordinates
Post by: Kitty Hello on 2009-Jan-22
why inline? Why ATAN2? The GLBasic ATAN _is_ atan2.
Title: Re: Moving between two sets of coordinates
Post by: Moru on 2009-Jan-22
Mabe this should be in the manual, MrTAToad here isn't the first to ask this. I was too slow to answer him on IRC though.
Title: Re: Moving between two sets of coordinates
Title: Re: Moving between two sets of coordinates
Post by: Schranz0r on 2009-Jan-22
ATAN == ATAN2 !

And works fine ;)
Title: Re: Moving between two sets of coordinates
Post by: Kitty Hello on 2009-Jan-22
See, the atan function just takes one argument, which is: dy/dx. Now, if you have atan2, you can have the atan behaviour: atan2(dy/dx, 1.0), as well as the (much better) atan2(dy,dx) version, which offers you 360 degree angles, whereas atan() dis not deciding on the quadrant:
-dy,dx is the same as dy,-dx.

Anyway.
Title: Re: Moving between two sets of coordinates
Thats true :)  Should have relaised that  :whistle:
Title: Re: Moving between two sets of coordinates
Post by: Hemlos on 2009-Jun-19
Old topic yes..
but theres another way i think, much easier for me to understand...

where: a2+b2=c2
distance x from origin to destination=Xdistance
distance y from origin to destination=Ydistance
hypotenuese=SQR(POW(Xdistance,2)+POW(Ydistance,2))
angle of origin x to destination x is CosAngle=ACOS(Xdistance/hypotenuese)
angle of origin y to destination y is SinAngle=ASIN(Ydistance/hypotenuese)

Results:
RELX=x+COS(CosAngle)*movesize
RELY=y+SIN(SinAngle)*movesize

Title: Re: Moving between two sets of coordinates
Post by: Schranz0r on 2009-Jun-20
Hey Hemlos, great work!

did you have ICQ installed?
you can PM your number ;)

I have some great ideas :P
Title: Re: Moving between two sets of coordinates
Post by: Hemlos on 2009-Jun-20
Thanks Schranz0r :)

For some reason the smtp server is timing out, is it because im in FLorida? :P
Title: Re: Moving between two sets of coordinates
Post by: Schranz0r on 2009-Jun-20

... is it because im in Florida? :P

Thats not fair! :D
Title: Re: Moving between two sets of coordinates
Post by: Hemlos on 2009-Jun-25
This topic went from making example of movement math,
to stirring up a particle engine system function set.  :good:

ps. check the beta section for the latest screenshot..it is in alpha testing still
Title: Re: Moving between two sets of coordinates
Post by: Schranz0r on 2009-Jun-25
little test (my solution):

Code: (glbasic) [Select]
`DRAWRECT 0,0,10,10, RGB(0xff, 0x00, 0x00)DRAWLINE 5,5,10,5, RGB(0x00, 0x00, 0x00)GRABSPRITE 0,0,0,10,10LOCAL x1=400,y1=100,x2=300,y2=250WHILE TRUE LOCAL winkel = ATAN(y1-y2,x1-x2)+180 INC x1,COS(winkel) INC y1,SIN(winkel) IF KEY(203) THEN DEC x2,3 IF KEY(205) THEN INC x2,3 IF KEY(200) THEN DEC y2,3 IF KEY(208) THEN INC y2,3 DRAWLINE x1+5,y1+5,x2+5,y2+5, RGB(0xff, 0xff, 0xff) ROTOSPRITE 0,x1,y1, -winkel ROTOSPRITE 0,x2,y2, -winkel+180SHOWSCREENWENDEND`
Title: Re: Moving between two sets of coordinates
Post by: Hemlos on 2009-Jun-25
Magic with Math! Beautiful  :enc: