The aim of this article is to show how to play a serie
of bitmaps at the location of the mouse cursor when the user clicks. In order
to do this, we are going to use the concepts of global list, behavior
and message parsing.
Firstly, we need a serie of bitmaps representing a complete
animation. To create a nice effect, the first and last bitmaps must be empty.
Below, an animation of 31 bitmaps of a dolphin once imported in the cast.
I found this animation on the
Internet as a .AVI file.
In Macromedia Director, the white colour
is used for transparency, so I imported the file into Microsoft
Gif Animator, exported each bitmap as .GIF, then converted
the blue background into a white one with Adobe Photoshop.
Then, I imported every bitmaps in Macromedia Director and
named them under the form of a letter followed by a number, the
serie begins with a white bitmap (ie. d0, d1, ..., d30).
In the draw window, one must check that the registration
point is the same for every bitmap, otherwise it will create a shift
when it animates.
The Lingo scripting is relatively easy, there are only
three scripts :
A script on startmovie which initializes
the global list free_sprites. This list contains the numbers
of sprites which can be used to start an animation.
A script on exitframe which manages the
clicks and the sending of starting messages to the sprites of the free_sprites
list.
A script behavior which locally manages
an animation, we will attach this script to every sprites.
Here is the detail of the three scripts :
on startmovie
global free_sprites
set free_sprites=[]
-- initialize an empty global list
end
on exitFrame
global free_sprites
if ((the mousedown=TRUE) and (count(free_sprites) <> 0)) then
-- IF the mousebutton is pressed
-- AND that the list is NOT empty THEN
sendsprite getat(free_sprites, 1), #start, point(the mouseh, the
mousev)
-- Send a starting message to the first sprite
of the list
-- IF the current bitmap if greater than the maximum
THEN
set mycurrent = 0
-- Put the current bitmap on the empty one
set mystart = 0
-- Stop the animation (trigger off)
add(free_sprites, mysp)
-- And add its sprite number to the free sprites
list
end if
set the member of sprite mysp to member string(myletter&mycurrent)
-- Refresh the current bitmap
end if
end
on start me, newloc
set the loc of sprite mysp to newloc
-- Put the sprite at the location indicated by newloc
set mystart = 1
-- put the trigger to on and so start the animation
on the next exitframe handler
deleteat(free_sprites, 1)
-- delete its number from the list
end
Finally, we must place the sprites on the stage,
take care to put the first member of the serie (d0) as it will not be visible
(empty bitmap). Then choose the transparent background and
attach the behavior to the sprite. Copy-Paste the sprite several
times, the number of sprites should be the number of bitmaps of the animation
+ 1 (ie. d0 .... d30 --> 32 sprites) in order to always have at least
one free sprite in the free_sprites list.
On the left, the result as a Shockwave movie. Click on
it to see the dolphins jumping out.
As a conclusion, it could be nice to transform this script
in order to re-use it easily. For that, we should setup the variables mymax
et myletter by putting them into a on getpropertydescriptionlist
handler. It is then possible to manage several animations by using several global
lists.
