Cool screen effect

[petree08]

This program randomly selects a point on the screen and a ball will follow it
this is done for a bunch of balls and it looks kinda cool

code:

const NUM_OF := 10 var X, Y : array 1 .. NUM_OF of int var XT, YT : array 1 .. NUM_OF of int procedure Blur_Screen     const BLUR_FACTOR := 50     for Blur : 1 .. BLUR_FACTOR         drawline (Rand.Int (1, 800) * 2 - 400, Rand.Int (1, 600) * 2 - 300,             Rand.Int (1, 800) * 2 - 400,             Rand.Int (1, 600) * 2 - 300, 7)     end for end Blur_Screen setscreen ("graphics:max,max,nobuttonbar,offscreenonly") colorback (7) cls const COLOUR := 12 const SIZE := 5 const MID_X := maxx div 2 const SPEED := 2 const MID_Y := maxy div 2 for Index : 1 .. NUM_OF     randint (XT (Index), 1, maxx)     randint (YT (Index), 1, maxy)     X (Index) := MID_X     Y (Index) := MID_Y end for loop     Blur_Screen     for Index : 1 .. NUM_OF         if X (Index) > XT (Index) - 2 and X (Index) < XT (Index) + 2 and                 Y (Index) > YT (Index) - 2 and Y (Index) < YT (Index) + 2 then             for Index2 : 1 .. NUM_OF                 randint (XT (Index2), 1, maxx)                 randint (YT (Index2), 1, maxy)             end for         else             if X (Index) > XT (Index) then                 X (Index) := X (Index) - SPEED             else                 X (Index) := X (Index) + SPEED             end if             if Y (Index) > YT (Index) then                 Y (Index) := Y (Index) - SPEED             else                 Y (Index) := Y (Index) + SPEED             end if         end if         drawfilloval (X (Index), Y (Index), SIZE, SIZE, COLOUR)     end for     View.Update end loop

[Cervantes]

First, you should take a look at the Turing Style Guideline. You're using way more whitespace than necessary, and you've got a pretty unconventional capitlizing/underscoring scheme.

Now, ordinarily, I would say, "Please DON'T post omfg sooo trippy cool flashes!", but this is a pretty cool effect. I just think it could use smoother animation. Wouldn't it be cool if the balls moved smoothly? How about if they moved under the effects of gravity?

Try this on for size.

code:

var balls : flexible array 1 .. 4 of     record         x, y, vx, vy, m : real         r : int     end record procedure blur_screen     for rep : 1 .. 40         drawline (Rand.Int (1, 800) * 2 - 400, Rand.Int (1, 600) * 2 - 300,             Rand.Int (1, 800) * 2 - 400,             Rand.Int (1, 600) * 2 - 300, 7)     end for end blur_screen setscreen ("graphics:900;900,nobuttonbar,offscreenonly") colorback (7) cls const G := 0.35 balls (1).x := maxx / 2 balls (1).y := maxy / 2 - 250 balls (2).x := maxx / 2 balls (2).y := maxy / 2 + 250 balls (1).vx := 8 balls (1).vy := 0 balls (2).vx := -8 balls (2).vy := 0 balls (3).x := maxx / 2 + 50 balls (3).y := maxy / 2 balls (4).x := maxx / 2 - 50 balls (4).y := maxy / 2 balls (3).vx := 0 balls (3).vy := 3 balls (4).vx := 0 balls (4).vy := -3 for i : 1 .. upper (balls)     balls (i).m := 100     balls (i).r := ceil (sqrt (balls (i).m / 3.14159)) end for loop     blur_screen     % Check for collisions     var ind := 0     loop         ind += 1         exit when ind > upper (balls)         for j : ind + 1 .. upper (balls)             var dist := Math.Distance (balls (ind).x, balls (ind).y, balls (j).x, balls (j).y)             if dist <= (balls (ind).r + balls (j).r) * 1.5 then                 % Combine balls i and j                 var total_mass := balls (ind).m + balls (j).m                 balls (ind).vx := ((balls (ind).vx * balls (ind).m) + (balls (j).vx * balls (j).m)) / total_mass                 balls (ind).vy := ((balls (ind).vy * balls (ind).m) + (balls (j).vy * balls (j).m)) / total_mass                 balls (ind).x := ((balls (ind).x * balls (ind).m) + (balls (j).x * balls (j).m)) / total_mass                 balls (ind).y := ((balls (ind).y * balls (ind).m) + (balls (j).y * balls (j).m)) / total_mass                 balls (ind).m := total_mass                 balls (ind).r := ceil (sqrt (balls (ind).m / 3.14159))                 % Remove ball j                 balls (j) := balls (upper (balls))                 new balls, upper (balls) - 1                 exit             end if         end for     end loop     % Update speeds     for i : 1 .. upper (balls)         % Apply gravity from other balls         for j : i + 1 .. upper (balls)             var dist := Math.Distance (balls (i).x, balls (i).y, balls (j).x, balls (j).y)             var force := G * balls (i).m * balls (j).m / (dist * dist)             var delta_x := balls (i).x - balls (j).x             var delta_y := balls (i).y - balls (j).y             balls (i).vx -= force * delta_x / dist             balls (i).vy -= force * delta_y / dist             balls (j).vx += force * delta_x / dist             balls (j).vy += force * delta_y / dist         end for         % Apply a repulsive force from the walls         balls (i).vx += G * balls (i).m ** 2 / (balls (i).x ** 2)         balls (i).vx -= G * balls (i).m ** 2 / ((maxx - balls (i).x) ** 2)         balls (i).vy += G * balls (i).m ** 2 / (balls (i).y ** 2)         balls (i).vy -= G * balls (i).m ** 2 / ((maxy - balls (i).y) ** 2)     end for     % Update positions and draw     for i : 1 .. upper (balls)         balls (i).x += balls (i).vx         balls (i).y += balls (i).vy         Draw.FillOval (round (balls (i).x), round (balls (i).y), balls (i).r, balls (i).r, red)     end for     View.Update     delay (12)     exit when hasch end loop

Let it run for a while. It doesn't get stuck in any particular orbit pattern (until the very end, when you only have one ball left).