Moving between two sets of coordinates

[MrTAToad]

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: 6.138

TYPE tMoveAlongLine
        ax
        ay
        ex
        ey
        bx
        by
        ix
        iy
        numSteps
        maxDistance
ENDTYPE

FUNCTION _dummy:
ENDFUNCTION

INLINE
        #include "math.h"
        extern double atan2 (      double y,      double x );
ENDINLINE

FUNCTION setTo:x,y
        moveAlongLine.ax=x
        moveAlongLine.ay=y
ENDFUNCTION

FUNCTION changeTo:bx,by
        moveTo(moveAlongLine.ax,moveAlongLine.ay,bx,by)
ENDFUNCTION

FUNCTION angleBetweenPoints:ax,ay,ex,ey
INLINE
        double angle;

        angle=atan2(ex-ax,ey-ay);
        if (angle<0.0)
        {
                angle=180.0+(180.0+angle);
        }

        return angle;
ENDINLINE
ENDFUNCTION

FUNCTION moveTo:sx,sy,fx,fy,mDistance=-1.0
LOCAL dx
LOCAL 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.numSteps
ENDFUNCTION

FUNCTION 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 TRUE
ENDFUNCTION
 

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 tMoveAlongLine

SETSCREEN 1024,768,0
moveTo(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

[Kitty Hello]

why inline? Why ATAN2? The GLBasic ATAN _is_ atan2.

[Moru]

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.

[MrTAToad]

I had thought ATAN2 would compile, but alas, its not found.

[Schranz0r]

ATAN == ATAN2 !


And works fine

[Kitty Hello]

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.

[MrTAToad]

Thats true   Should have relaised that 

[Hemlos]

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

[Schranz0r]

Hey Hemlos, great work!

did you have ICQ installed?
you can PM your number

I have some great ideas

[Hemlos]

Thanks Schranz0r  

For some reason the smtp server is timing out, is it because im in FLorida?

[Schranz0r]

... is it because im in Florida?

Thats not fair!

[Hemlos]

This topic went from making example of movement math,
to stirring up a particle engine system function set. 

ps. check the beta section for the latest screenshot..it is in alpha testing still

[Schranz0r]

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 0,0,0,10,10


LOCAL x1=400,y1=100,x2=300,y2=250

WHILE 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+180


SHOWSCREEN
WEND
END

 

[Hemlos]

Magic with Math! Beautiful