Graphing a Line Problem (Math)

[Kid_Roleplay]

I'm trying to create an invisible line formed by the direction an object is facing and its current hotspot, and when the Y value of another object is greater than a spot on that line (determined by that object's X position), then "do something." In this case, I just made it paste to the background repeatedly so I can see where the math actually draws the line. I'm not sure how to make this work, and what I do have works even worse at different angles. Any help would be appreciated.

An example .mfa is attached for what I've gotten so far.

[Kid_Roleplay]

...

[King_Cool]

Something like this?

[Kid_Roleplay]

Pretty close, ya. I think I might be able to use that, but just speculating. The only problem I have with that is that it looks like it requires a detector object, and testing the Y position of the object that changes colors has to be aligned with that detector and changes colors based on the hotspot instead of possibly being above or below a line drawn by a direct path to the rotating object and the detector object.

What I'm trying to make can't move so freely.

--- After testing that out further, it still doesn't work.

[MuddyMole]

We know the formula for a straight line is: Y = MX + C

To find M (the gradient), we use trigonometry:
M = (0-Sin(Angle( "Line" )))/Cos(Angle( "Line" ))

To find C (the intercept), we rearrange the original formula, and substitute the X and Y coordinates of a point we know is somewhere along the line (we can use the line object's hotspot).

C = Y( "Line" )-(M*X( "Line" ))

Now that we know both M and C, we can solve for Y:

If Y position of Object < (M*X( "Object" ))+C
...then the object is above the line.

eg.
http://skydrive.live.com/redir?resid...094271BBDA!544

[Kid_Roleplay]

Exactly what I needed! Thank you, kind sir. You are a gentleman and a scholar!