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traugott.simon



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4th February, 2009 at 17:43:37 -

Hi!

Simple question:
Is it possible to get the exact point between two crossing actives (simple lines)?

 
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noPE

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4th February, 2009 at 17:49:43 -

example?

 
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traugott.simon



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4th February, 2009 at 18:09:43 -

you need an example from me?

lets say two lines cross. both different actives. i need to get the coordinates of the point, where these lines cross.

 
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noPE

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4th February, 2009 at 18:20:23 -

i know what you mean. but your wording or your thinking is off. actives are not lines. actives have a single x and a singe y coordinate. lines (technically line segments) have AT LEAST two coordinates (x1, y1) - (x2, y2).

 
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traugott.simon



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4th February, 2009 at 18:37:37 -

yes ok u r right. i have to use actives, so there should be a way to detect overlapping pixels. i´m not sure if this is possible, i guess not.

 
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Pixelthief

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4th February, 2009 at 19:02:48 -

If you can know with certainty where the Active Object lines begin and end, its possible to determine through math where they intersect.


If you had the Hot Spot at one end of the line and the Active Spot at the other end, then you could retrieve these in the expression editor to find out the coordinates of each side of the line. From these coordinates, you can plug them into an equation to find the intercept of two straight lines.

 
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Sketchy

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4th February, 2009 at 20:32:18 -

Job done
http://cid-b1e7ee094271bbda.skydrive.live.com/self.aspx/Public/intercept.mfa

Don't ask me to explain - if you want to know how it works, Google "calculate intercept two lines" or something like that.

Edited by Sketchy

 
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traugott.simon



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4th February, 2009 at 20:49:14 -

well sketchy thats exactly what i needed! now i hope i understand your code and can use it for my project! thx alot

 
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Sketchy

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4th February, 2009 at 21:25:02 -

Okay, I will give a brief explanation after all...

It's all based on the formula of a straight line...
y = (m*x) + c

First, calculate "m" for each line. "m" is the slope, and is calculated using a little trigonometry...
m = (sin(angle) * -1) / cos(angle)

Next, calculate "c" for each line. "c" is the intercept, and is calculated by rearranging our original formula so...
c = y - (m*x)

Now, we know that...
y = (m1*x) + c1
y = (m2*x) + c2

So where the two lines intersect...
(m1*x) + c1 = (m2*x) + c2

A bit more algebra later and we find that...
x = (c2 - c1) / (m1 - m2)

Now we know "x", we can use it to solve our original formula for one of the lines...
y = (m1*(c2 - c1) / (m1 - m2)) + c1

 
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noPE

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4th February, 2009 at 21:39:04 -

aw sketchy beat me two it.

actually pretty spiffy using the angle to get the slope. that way you DONT have to have both ends of the line. you do however have to check whether the two actives are overlapping. otherwise it will give you a spot somewhere off in the distance.

 
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