> I'm currently looking at storing the animation progress of each of my ten
> objects and moving each one bit by bit within a repeat loop.
> Does anybody else know of a better method of performing this task? Is there
> a series of commands that already exist in lingo that allow me to say "Move
> 200 pixels to the left at speed 4" ?
Don't use a repeat loop. You can use a frame loop, but that relies on frame
rate. A better way is to drive your animation with a timeout object.
Normally, I'd leave you with that advice and let you work through it, but I
happen to have written a behavior that will move a sprite in a straight line
to a destination point (not just horizontal or vertical - to get that
motion, you'd just give the behavior a destination point that has the same
locH or locV value as the sprite's starting point).
I'm sure there are ways to optimize... that's a hint, people - I'd love to
see ways to improve it.
HTH,
Kurt
Watch out for email-induced line breaks.
------------------
Property pDestination -- The point to which this sprite will travel
Property pSpeed -- The time it will take this sprite to get there
Property pChangePoint -- Increment to change the loc of the sprite at each
callback
Property pTimer -- Timeout object to drive things
Property pMySprite -- Duh
Property pFloatingLoc -- Stores the change in loc in floats, so as to avoid
a "round down" with changes that are less than .5
---------------------
on getPropertyDescriptionList
pdl = [:]
pdl.addProp(#pDestination,[#comment:"where do you want to go today?",
#format:#point, #default:point(0,0)])
pdl.addProp(#pSpeed,[#comment:"How long to get there (in milliseconds)?",
#format:#integer, #default:5000])
return pdl
end getPropertyDescriptionList
---------------------
on new me, destination, speed
pDestination = destination
pSpeed = speed
return me
end
---------------------
on beginSprite me
pMySprite = sprite(me.spriteNum)
-- Determine the overall change in x and y positions
dx = pDestination.locH - pMySprite.locH
dy = pDestination.locV - pMySprite.locV
-- The larger distance will determine the frequency of the callbacks
-- from the timeout object
numberOfSteps = max(abs(dx), abs(dy))
-- Keeping things simple. We're going to move one pixel on the larger axis
at each callback,
-- and a fraction of a pixel on the smaller axis, determined by the slope
of
-- line equation.
deltaRatio = abs(float(dy)/dx)
-- Need to know whether to travel left or right
if dx < 0 then
xDirection = -1
else
xDirection = 1
end if
-- Need to know whether to travel up or down
if dy < 0 then
yDirection = -1
else
yDirection = 1
end if
-- The larger axis gets the change in loc of 1 (or negative 1), and the
smaller
-- gets a fractional change. The fraction gets multiplied by the
directional variable,
-- otherwise the sprite would always move right or down.
if numberOfSteps = abs(dx) then
pChangePoint = point(xDirection, deltaRatio*yDirection)
else
pChangePoint = point(xDirection/deltaRatio, yDirection)
end if
-- Necessary to store a separate loc with floats, because simply setting
-- pMySprite.loc = pMySprite.loc + pChangePoint rounds off fractions less
than .5,
-- as "loc"s (when a property of a sprite) are integer-based.
pFloatingLoc = point(float(pMySprite.loc).locH, float(pMySprite.loc).locV)
--Unique name for the timeout object
timername = string(me)
pTimer = timername.char[timername.char.count - 8..timername.char.count]
-- Create the timer. we are going numberOfSteps number of pixels in pSpeed
-- time, so the callbacks need to happen every float(pSpeed)/numberOfSteps
-- milliseconds.
temp = timeOut(pTimer).new(float(pSpeed)/numberOfSteps, #mMove, me)
end beginSprite
---------------------
on mMove me
-- If the sprite is not within a pixel of its destination, move it some
more.
if abs(pDestination.locH - pMySprite.locH) > 1 then
pFloatingLoc = pFloatingLoc + pChangePoint
pMySprite.loc = pFloatingLoc
else
-- This is the last stop. Please take any personal belongings with
-- you as you exit the train.
death = timeOut(pTimer).forget()
-- Tidy up (that locV value may be a bit off, so this will get us to the
end)
pMySprite.loc = pDestination
end if
end mMove
---------------------
on endSprite me
-- Kill the engineer
death = timeOut(pTimer).forget()
end endSprite
---------------------
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