Line Tracing

[Jan Schenkel]

--- Roger Guay <rogerguay at centurytel.net> wrote:
> Sarah, Jim
> 
> What I'm trying to do is trace a line in time as a
> ball is moved across 
> the screen.  Near as I can tell, I want the screen
> to update but not 
> redraw (if that makes any sense?)  I've done this in
> ToolBook on the PC 
> but I much prefer to stay on my Mac.  Here is a
> description of my stack:
> 
> Create a vertical line and label it "Yaxis" and an
> horizontal line and 
> Label it  "Xaxis" such that they intersect and
> define the origin  
> somewhere near the lower left corner of your stack. 
> Create a brightly 
> colored circle graphic and name it "Ball."  Create 2
> fields, one for 
> Theta so labeled which defines the angle from the
> horizon that the ball 
> is being fired, and one for V so labeled which
> defines the velocity of 
> the ball when fired.  Create a "Fire" button and
> insert the following 
> script:
> 
> on MouseUp
>    global V, Xo, Yo, Theta, T, X
>    --put item 1 of the rect of graphic "Yaxis" into 
> Xo.  Yaxis is a 
> vertical line and Xo,Yo define the origin of motion
>    --put item 4 of the rect of graphic "Yaxis" into 
> Yo.
>    put field "V" into V    ---- try a value of about
> 27 in field "V"
>    Put the value of field "Theta" into Theta 
> ----try a value of 1.2 in 
> field "Theta"
>    set the loc of graphic "mortor" to Xo,Yo   ----
> Graphic "mortor" is a 
> small red round ball.
>    show graphic "mortor"
>    put 0 into T
>    put xo into x
>    put Yo into y
>    play "Mortor.aiff"
>    repeat while Y <= Yo + 1
>      add 1 to T
>      put the value of (Xo+V*cos(Theta)*T     ) into
> x
>      put the value of (Yo - V*sin(Theta)*T + .5*T^2 
> ) into Y
>      set the loc of graphic "mortor" to X,Y
>      wait 1
>    end repeat
> 	----------  the rest of the script results in a
> silly explosion at the 
> last location of the mortor -------
>    play  "Boom.aiff"
>    hide graphic "mortor"
>    set the loc of graphic "Burst" to x,Yo
>    repeat 35
>      show graphic "burst"
>      wait 1
>      hide graphic "burst"
>      wait 1
>    end repeat
> end MouseUp
> 
> 
> 
> Jim has actually provided a solution for me that
> works well if I insert 
> "wait .01" in his repeat loops.  I can only assume
> it has something to 
> do with processing speed of the computer (I'm using
> a high end iMac 
> with OS X.)  Without the "wait" command in the
> repeat loop, Jim's 
> scripts are very choppy on my computer.
> 
> Finally, as I say, Jim's solution works well but I
> think it would 
> nevertheless be more "elegant" to do this as I have
> in ToolBook where 
> one is able to stop the screen redraw.
> 
> Thanks very much for joining in the fun, Roger
> 

Hi Roger,

Have you had a look at the 'move' command? It's at the
heart of the RunRev Animation Manager, and you should
be able to create a smooth movement by setting a
series of points and letting the object travel along
those points with a 'move' statement.

Just a thought,

Jan Schenkel.

=====
"As we grow older, we grow both wiser and more foolish at the same time."  (La Rochefoucauld)

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