Programming and Scripting :: some math help please?



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since you're taking the squares of the distance, you don't need to take the absolute values of each component
I didn't know that. Thanks.
EDIT: seems like it is needed after a quick test

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Also, it seems that there is always a gravity point at the top left corner (0,0)?
I'd seen that in other tests as well. Since I don't know real math, I just ignored that. I think I've got that fixed, though, as well as the problem with all objects always moving at 45 degree angles.

I messed around with the numbers for a while and came up with something else I like. So far I see one problem with it, that the objects gravitate toward a single x,y intersection over time if you don't move the mouse.
Code Sample
balls=1500
bsize=2
min_grav=0
max_grav=6

function grav_loop()
local my_x,bx=Fl:event_x(),0
local my_y,by=Fl:event_y(),0
local c=math.random(1,255) -- random color
 for i=1,balls do
   local xdistance=math.abs(my_x-ball[i]:x())
   local ydistance=math.abs(my_y-ball[i]:y())
   local distance=math.sqrt(xdistance*xdistance+ydistance*ydistance)
   local xspeed=(min_grav+max_grav)/distance*xdistance
   local yspeed=(min_grav+max_grav)/distance*ydistance
   if distance <= 25 then -- warp it offscreen
     ball[i]:color(c)
     xspeed=xspeed*max_x/distance*math.random(2,3)
     yspeed=yspeed*max_y/distance*math.random(2,3)
   end      
   if my_x > ball[i]:x() then bx=ball[i]:x()+xspeed else bx=ball[i]:x()-xspeed end
   if my_y > ball[i]:y() then by=ball[i]:y()+yspeed else by=ball[i]:y()-yspeed end
   ball[i]:position(bx,by)
 end
w:redraw()
grav_timer:doWait(.05)
end

w=fltk:Fl_Double_Window(Fl:w(),Fl:h(),"gravity test")
w:color(0)

math.randomseed(os.time())
max_x=w:w()-bsize
max_y=w:h()-bsize
ball={}
for i=1,balls do
ball[i]=fltk:Fl_Box(math.random(1,max_x),math.random(1,max_y),bsize,bsize)
ball[i]:box(fltk.FL_FLAT_BOX)
end

grav_timer = murgaLua.createFltkTimer()
grav_timer:callback(grav_loop)
grav_timer:do_callback()

w:fullscreen()
w:show()
Fl:run()

EDIT: fixed a typo
Quote
I messed around with the numbers for a while and came up with something else I like. So far I see one problem with it, that the objects gravitate toward a single x,y intersection over time if you don't move the mouse.
If you could decide that point, it could be desired behavior. I suggest setting it to the center of the display.
That wouldn't be very useful, though, If this turns into something I might want to use as a screensaver.  When I say an intersection, I mean all objects gravitate to travelling along either a single x coordinate or a single y coordinate, so what you have on screen is essentially just two lines that intersect at the location of the cursor.
Quote (mikshaw @ Jan. 23 2008,15:03)
Quote
since you're taking the squares of the distance, you don't need to take the absolute values of each component
I didn't know that. Thanks.
EDIT: seems like it is needed after a quick test

That was just for your first one where you only used the direct distance.

Your 2nd one is looking better too - but seeing the same problems that you have described.

Took at look at your 2nd one... not sure if you already have something like this:
Code Sample
-- snip
  local yspeed=(min_grav+max_grav)/distance*ydistance
-- cut out if statement
  if my_x > ball[i]:x() then bx=ball[i]:x()+xspeed else bx=ball[i]:x()-xspeed end
  if my_y > ball[i]:y() then by=ball[i]:y()+yspeed else by=ball[i]:y()-yspeed end
-- add back warp
  if distance <= 25 then -- warp it
    ball[i]:color(b)
    bx = math.random(1,max_x)
    by = math.random(1,max_y)
  end
-- /snip
This doesn't make the new dots offscreen though... did you want to specifically do that?
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This doesn't make the new dots offscreen though... did you want to specifically do that?
Yeah, It pretty much just shoots them forward a ways, but I don't really understand how much. It looks like somewher between halfway across the screen to waaay outside the screen.  I'm working on a different method now that should place them just offscreen and also hopefully cut down on the processing a little.
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original here.