Folk Computer

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====== ORBITALKIT ======

{{folkarc:orbitalkit:programs.mp4?200 | An instance of ORBITALKIT}}

Current issues:

  * The speed which the actual circle orbits rotate at are really off


===== Source =====

<file tcl>
# ORBITALKIT - CC0 2023 Arcade Wise
# Create a planet using "Claim $this is Earth"
# Create a satellite using "Claim $this is a satellite"
 
 
proc orbitalVelocityAroundEarth {radius} {
    set EarthMass [expr {5.972168 * (10 ** 18)}]
    set G [expr {6.67430 * (10.0 ** (-11.0))}]
 
    return [expr {sqrt(($G * $EarthMass) / $radius)}]
} 
 
 
When /someone/ claims /earth_page/ is Earth {
    When $earth_page has region /earth/ {
        # Draw a little earth :>
        lassign [region centroid $earth] x_earth y_earth

        Wish to draw a circle with x $x_earth y $y_earth radius 100 thickness 5 color green 
 
        Wish $earth_page is labelled Earth
 
        When /someone/ claims /sat_page/ is a satellite  { 
            When $sat_page has region /sat/ & the clock time is /t/ & /sat/ has tag /tag/ {
                set radius [vec2 distance [region centroid $earth] [region centroid $sat]]
                
                # Display the orbit circle
                Wish to draw a circle with x $x_earth y $y_earth radius $radius thickness 5 color darkblue filled false 

                set speed [orbitalVelocityAroundEarth [expr {$radius * 1000}]]
            
                # Calculate postion for sattelite
                set angle [expr {(round(($t * 200 + ($tag * 100))) % 2000) / 2000.0}]
                set x [expr {($radius * sin(6.283 * $angle )) + $x_earth}]
                set y [expr {($radius * cos(6.283 * $angle )) + $y_earth}]

                # display the stroke 
                Wish to draw a stroke with points [list [region centroid $earth] [list $x $y]] width 1 color red
 
                Wish to draw a circle with x $x y $y radius 20 thickness 5 color white filled true

                Wish to draw text with x $x y [expr {$y - 40 }] scale 1 text "[expr {round($speed)}]km/s at [expr {int($radius) * 1000}]km from Earth" radians [region angle $earth]
            } 
        }
    }
}

When tag /tag/ has corners /corners/ & /tag/ has region /region/ {
  Claim $region has tag $tag
}
</file>