Re: Intersect Function
I believe the OP was talking about two arbitrary lines, likely graphic objects, that intersect each other. Not rectangles with points within them, or two rectangles. I think the only way to do this is as per the first four posts in this thread. Craig -- Sent from: http://runtime-revolution.278305.n4.nabble.com/Revolution-User-f278306.html ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
> Jerry J. wrote: > I think he mentioned curved “lines”. That is a > whole other kettle of fish. The OP speaks of "functions for the lines", so either he means "math lines" or, as you say, continuous curves, say polynomials. Yes, this isn't solvable for polynomials of higher degree by formulas (not because mathematicians didn't find the formula, to the contrary, it is proved that there is no formula for that). So the solution is a numerical one, finding the roots of (say for simplicity) polynomials. There are several fast algorithms for that. One of the simplest (and usually fast enough) is the Newton-Raphson method. https://en.wikipedia.org/wiki/Newton%27s_method A trial and error method as proposed by Craig may be good enough for very simple curves. This is also a (good) pragmatic approach. On the other hand the Newton-Raphson method is simple to script. https://en.wikipedia.org/wiki/Newton%27s_method As LC can not differentiate, you have to do that by yourself before applying it. [For non-math people: The intersection point of two functions is a root finding problem, because searching the point x where f1(x)=f1(x) is the same as finding the "root" (zero point g(x)=0) of g(x)= f1(x)-f2(x).] ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
It is, and INTERSECT with them is just a distraction. Probably time (shock, horror) to do some Mathematics. On Mon, Sep 24, 2018, 11:36 PM Jerry Jensen via use-livecode < use-livecode@lists.runrev.com> wrote: > I think he mentioned curved “lines”. That is a whole other kettle of fish. > .Jerry > > > On Sep 24, 2018, at 9:23 AM, hh via use-livecode < > use-livecode@lists.runrev.com> wrote: > > > > It is not this complicated. Only if you are looking for > > the intersection of two line *segments* you have do a > > few more checks. > > > ___ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your > subscription preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
One could have a line consisting of a graphic object (rectangle) with a width of one. ? On Mon, Sep 24, 2018, 10:17 PM hh via use-livecode < use-livecode@lists.runrev.com> wrote: > @Richmond. > > You (and the author) overlooked that we have, since 1.0, > is within . > > ___ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your > subscription preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode > ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
I think he mentioned curved “lines”. That is a whole other kettle of fish. .Jerry > On Sep 24, 2018, at 9:23 AM, hh via use-livecode > wrote: > > It is not this complicated. Only if you are looking for > the intersection of two line *segments* you have do a > few more checks. ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
@Richmond. You (and the author) overlooked that we have, since 1.0, is within . ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
I found THIS in the User contributed notes in the 7.1.4 documentation from 2009: "The intersect() command takes two objects as inputs. In some situations, it may be useful to find the intersect of a point and a rectangle. The custom function below may be used in those cases: function pointIntersect pPoint,pRect split pPoint by comma split pRect by comma return ((pRect[1] <= pPoint[1]) and (pPoint[1] <= pRect[3]) and (pRect[2] <= pPoint[2]) and (pPoint[2] <= pRect[4])) end pointIntersect Examples: pointIntersect(the mouseLoc, the rectangle of stack "MyStack") pointIntersect(the clickLoc, the rect of img "Splash") Use the pointIntersect function to determine whether a point is within a specified rectangle. Parameters: The pPoint is an expression that evaluates to a point. The pRect is a rectangle consisting of four integers separated by commas. Value: The pointIntersect function returns true or false. Comments: The pointIntersect function does not differentiate between screen coordinates and window coordinations. This means that if the point is screen-relative, such as a mouseLoc, and the rectangle is window-relative, such as an object's rectangle, the pointIntersect function does not return a reliable result." This is NOT mine, so I can take no credit for it. Richmond. ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
It is not this complicated. Only if you are looking for
the intersection of two line *segments* you have do a
few more checks.
A LC object "line" is a line segment given by two pairs
of points (x,y).
The OP probably mean with line the math object line that is
given by and passing through these pair of points.
For example to get the intersection of two lines (if not
parallel) this works here.
-- pts1 = two lines of points from the first LC-"line"
-- pts2 = two lines of points from the second LC-"line"
function lineIntersection pts1,pts2
put pts1 & pts2 into p
repeat with i=1 to 4
put item 1 of line i of p into x[i]
put item 2 of line i of p into y[i]
end repeat
put (y[4]-y[3])*(x[2]-x[1]) \
- (y[2]-y[1])*(x[4]-x[3]) into d
if abs(d) < 0.1 then
return "parallel"
else
put (x[4]-x[3])*(x[2]*y[1]-x[1]*y[2]) \
- (x[2]-x[1])*(x[4]*y[3]-x[3]*y[4]) into xn
put (y[1]-y[2])*(x[4]*y[3]-x[3]*y[4]) \
- (y[3]-y[4])*(x[2]*y[1]-x[1]*y[2]) into yn
end if
return format ("%0.3f,%0.3f", xn/d, yn/d)
end lineIntersection
on mouseUp
put the points of grc 1 into p1
put the points of grc 2 into p2
if there is no grc "ip" then
create grc "ip"
set style of grc "ip" to "oval"
set rect of grc "ip" to (0,0,10,10)
set foreColor of grc "ip" to "255,0,0"
set lineSize of grc "ip" to 1
end if
put lineIntersection(p1,p2) into ip
put ip into fld "info"
if ip is not "parallel" then
set loc of grc "ip" to \
round(item 1 of ip),round(item 2 of ip)
end if
end mouseUp
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Re: Intersect Function
Well and good. I repeat that in a computer screen, with fixed pixel coordinates, you will likely need just a bit of rounding forgiveness when doing the math. You need to write a bit of code, in other words, that will accept close matches between the string of pixels and the calculated "points" along the line. Craig -- Sent from: http://runtime-revolution.278305.n4.nabble.com/Revolution-User-f278306.html ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
Thanks Craig, I was already afraid of that. Yes, I guess I could figure out the math. I will have the 2 functions of the lines and if I set them equal, I could solve the intersection point of the two. Your way is also valid, but as I need to determine many intersection points, the script might get slow. Of course your way might prove better if we're looking at curves. The amount of points in a curved line increases some in comparison to a straight line, but in setting the functions equal, I'd have to deal with quadratic functions. It just comes to me, that that is quite doable : move everything to one side of the equal sign and apply the famous 'abc formula' (at least that it was called in my high school years in Holland). It's used to solve a quadratic equation. Once the 'x' is known, I can put it into one of the functions to get the 'y' coordinate. I will see what goes faster. Cheers, Beat On Mon, Sep 24, 2018 at 3:15 PM dunbarxx via use-livecode < use-livecode@lists.runrev.com> wrote: > Hi. > > No. > > But you can determine the points of a line graphic, and calculate all the > pixels it "contains" from its starting point to its ending point. Do the > same for a second line. > > Then you can determine the point that seems to be common to both lines. I > say seems, because when you do the math, that is, using the slope of each > line and calculating the points using that information, you may find that > there are no exact matches. But you can allow a small differential, and the > closest pair of points will be the one you want. > > Can you do the math? > > Craig Newman > > > > -- > Sent from: > http://runtime-revolution.278305.n4.nabble.com/Revolution-User-f278306.html > > ___ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your > subscription preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode > ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Intersect Function
Hi. No. But you can determine the points of a line graphic, and calculate all the pixels it "contains" from its starting point to its ending point. Do the same for a second line. Then you can determine the point that seems to be common to both lines. I say seems, because when you do the math, that is, using the slope of each line and calculating the points using that information, you may find that there are no exact matches. But you can allow a small differential, and the closest pair of points will be the one you want. Can you do the math? Craig Newman -- Sent from: http://runtime-revolution.278305.n4.nabble.com/Revolution-User-f278306.html ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Intersect Function
Is there a function to determine the intersection point (x,y) of two lines? The intersect function in LC only gives me a true or false, and I need the exact location (x,y) of the intersection. Thanks, Beat ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
