Arjen Markus (23 october 2002) As a sequel to the page Creating an animated display here is a script that incorporates two separate displays working in the same framework. I added a little user-interface to make it work smoother.
# animdemo.tcl --
# A few simple animated displays
#
#
# Animation --
# Namespace to hold all (specific) information
#
namespace eval ::Animation:: {
variable xmouse 0 ;# Make sure they have a value
variable ymouse 0
}
# StoreMousePosition --
# Store the coordinates of the mouse pointer for later use
#
# Arguments:
# xp X-coordinate of the mouse
# yp Y-coordinate of the mouse
#
# Result:
# None
#
proc ::Animation::StoreMousePosition {xp yp} {
variable xmouse
variable ymouse
set xmouse $xp
set ymouse $yp
}
# drawBall --
# Draw a red circle at a certain height above the green ground
#
# Arguments:
# time Time parameter, used to calculate the actual height
#
# Result:
# None
#
# Note:
# Assume a perfectly elastic collision. The time parameter must
# be reduced to the time since the last collision.
#
# Technique used: redraw the entire picture
#
proc ::Animation::drawBall {time} {
global accel
global velo0
global cnv_height
global cnv_width
set period [expr {2.0*$velo0/$accel}]
set time2 [expr {$time - $period * int($time/$period)}]
set grass_height 20
set radius 7
set ball_height [expr {$velo0*$time2-0.5*$accel*$time2*$time2}]
set pix_height [expr {
$cnv_height-$grass_height - $radius - $ball_height}]
set xl [expr {0.5*$cnv_width-$radius}]
set xr [expr {0.5*$cnv_width+$radius}]
set yb [expr {int($pix_height)-$radius}]
set yt [expr {int($pix_height)+$radius}]
.cnv delete all
.cnv create rectangle 0 $cnv_height $cnv_width \
[expr {$cnv_height-$grass_height}] -fill green -outline green
.cnv create oval $xl $yb $xr $yt -fill red -outline black
}
# drawCompassNeedles --
# Draw a set of compass needles that orient themselves to the
# current mouse position
#
# Arguments:
# time Time parameter, ignored
#
# Result:
# None
#
# Note:
# The mouse position is stored via the binding to the mouse event
# motion. We use only this information to create a new display.
#
# Technique used: redraw the picture
proc ::Animation::drawCompassNeedles {time} {
variable xmouse
variable ymouse
set hlength 14
set hwidth 7
.cnv delete all
foreach y {10 50 90 130 170 210 250 290} {
foreach x {10 50 90 130 170 210 250 290 330 370} {
set dx [expr {$xmouse-$x}]
set dy [expr {$ymouse-$y}]
if { $dx != 0 || $dy != 0 } {
set angle [expr {atan2($dy,$dx)}]
} else {
set angle 0
}
set cosa [expr {cos($angle)}]
set sina [expr {sin($angle)}]
set x1 [expr {$x+$hlength*$cosa}]
set y1 [expr {$y+$hlength*$sina}]
set x2 [expr {$x+$hwidth*$sina}]
set y2 [expr {$y-$hwidth*$cosa}]
set x3 [expr {$x-$hlength*$cosa}]
set y3 [expr {$y-$hlength*$sina}]
set x4 [expr {$x-$hwidth*$sina}]
set y4 [expr {$y+$hwidth*$cosa}]
.cnv create polygon $x1 $y1 $x2 $y2 $x4 $y4 \
-fill red -outline black
.cnv create polygon $x3 $y3 $x2 $y2 $x4 $y4 \
-fill blue -outline black
}
}
}
# nextPicture --
# Prepare to call the next picture, stop after some predefined
# number of steps.
#
# Arguments:
# step Step number (converted to time)
#
# Result:
# None
#
proc nextPicture {step method} {
global time_delay
global max_steps
global stop_anim
#
# Draw the picture
#
$method [expr {0.1*$step}]
#
# Set up the next picture via the [after] command
#
if { $step < $max_steps && $stop_anim != 1} {
incr step
after $time_delay [list nextPicture $step $method]
}
}
# stopPicture --
# Stop the animation
#
# Arguments:
# None
#
# Result:
# None
#
# Side effect:
# Sets the variable "stop_anim" to gracefully stop the animation
#
proc stopPicture {} {
global stop_anim
set stop_anim 1
}
# main --
# Set up the canvas, start the loop
#
global cnv_width
global cnv_height
global velo0
global accel
#
# Canvas size
#
set cnv_width 400
set cnv_height 300
#
# Time delay and maximum duration (steps)
#
set time_delay 100 ;# Time in ms between pictures
set max_steps 1000 ;# Maximum number of steps
#
# Private variable to stop the animation if wanted
#
set stop_anim 0
#
# Needed for drawBall
#
set velo0 70.0 ;# m/s
set accel 10.0 ;# m/s2
;# pixels become m that way :)
#
# Set up the canvas and the buttons
#
canvas .cnv -width $cnv_width -height $cnv_height -background white
frame .frm1
radiobutton .frm1.ball -text "Bouncing ball" \
-variable method -value "::Animation::drawBall" \
-command {stopPicture}
radiobutton .frm1.compass -text "Compass needles (following mouse)" \
-variable method -value "::Animation::drawCompassNeedles" \
-command {stopPicture}
pack .frm1.ball .frm1.compass -side left
frame .frm2
button .frm2.start -text "Start" \
-command {set stop_anim 0; nextPicture 0 $method}
button .frm2.stop -text "Stop" -command {stopPicture}
pack .frm2.start .frm2.stop -side left
pack .frm2 -side bottom -fill x
pack .frm1 -side bottom -fill x
pack .cnv -fill both
bind .cnv <Motion> {::Animation::StoreMousePosition %x %y}
set method ::Animation::drawBall
$method 0
#
# If you want the animation to start rightaway ...
#
#nextPicture 0 $method[ Arts and cratfs of Tcl-Tk programming