Running once... In a loop?

[Grim]

What is it you are trying to achieve?
I'm trying to create a game using Pac-Man. I am using whatdotcolour for collision detection, but because that code has to be in the same loop as my draw commands, I am re-drawing my background every time, causing an annoying flicker.

Describe what you have tried to solve this problem
Nested loop, Nested for loop, nested decreasing for loop, placing draw command outside loop


Here's the code...

Turing:

loop         collision := false         mouth := mouth mod 45 + 1   % change size of the mouth         drawfillarc (x, y, 20, 20, mouth + dir, -mouth + dir, yellow) delay (5)         drawfillarc (x, y, 20, 20, mouth + dir, -mouth + dir, black)         x := x + xx         y := y + yy         Draw.FillBox (0,0,1000,1000,brightblue)         Draw.FillBox (20, 20, maxx - 20, maxy - 20, black)         Draw.FillBox (300, 0, 340, 150, brightblue)         Draw.FillBox (300, 250, 340, 400, brightblue)         if whatdotcolor (x, y) not= black then             x -= xx             y -= yy             collision := true         end if      end loop

Any possible way of making that draw command run only once?

[DanShadow]

If flickering is your issue, using:
View.Set ("graphics,offscreenonly")
should fix your problem.

Alternatively, you can draw your background outside your loop, and every time pacman moves you can redraw a portion of the background where pacman used to be (before he moved). Im guessing the background would be black, so pretty easily done.

View.Set("graphics,offscreenonly") is probably a lot easier though.

[Grim]

I'll post the whole program. The flickering is caused because every time my loop runs, it re-draws the background. Perhaps this will show you what I mean.

Turing:

var dx, dy : int                    % direction Pacman moves var mouth : int := 0                % size of mouth var dir : int := 0                  % mouth direction, 0=right, 90=up, etc. var xx : int := 0 var yy : int := 0 var collision : boolean := false var check : int := 1 const mup := chr (200) const mdown := chr (208) const mleft := chr (203) const mright := chr (205) dx := 1 dy := 0 process movement     loop         var key : array char of boolean         loop             xx := round (dx)             yy := round (dy)             Input.KeyDown (key)             if key (mup) then                 dir := 90                 dx := 0                 dy := 1             elsif key (mdown) then                 dir := 270                 dx := 0                 dy := -1             elsif key (mleft) then                 dir := 180                 dx := -1                 dy := 0             elsif key (mright) then                 dir := 0                 dx := 1                 dy := 0             end if         end loop     end loop end movement fork movement process coll     loop         collision := false         mouth := mouth mod 45 + 1   % change size of the mouth         drawfillarc (x, y, 20, 20, mouth + dir, -mouth + dir, yellow)         delay (5)         drawfillarc (x, y, 20, 20, mouth + dir, -mouth + dir, black)         x := x + xx         y := y + yy         Draw.FillBox (0,0,1000,1000,brightblue)         Draw.FillBox (20, 20, maxx - 20, maxy - 20, black)         Draw.FillBox (300, 0, 340, 150, brightblue)         Draw.FillBox (300, 250, 340, 400, brightblue)         if whatdotcolor (x, y) not= black then             x -= xx             y -= yy             collision := true         end if       end loop end coll

I know processes are a no-no around here, but this seemed the easiest way to do it at the time.

[TheGuardian001]

Grim @ Thu Oct 21, 2010 8:48 pm wrote:

I know processes are a no-no around here, but this seemed the easiest way to do it at the time.

It's not. Processes will basically guarantee flickering, even if you use View.Set("offscreenonly"), which you should be using.

Your layout should look something like this:

code:

declare variables View.Set("offscreenonly") %Don't draw anything to the screen until we say so procedure movement %procedure, not process     %NO LOOPS ALLOWED IN HERE     movement code     %NO LOOPS ALLOWED IN HERE end movement procedure coll %again, not a process     %NO LOOPS ALLOWED IN HERE      drawing code      %NO LOOPS ALLOWED IN HERE end coll %Main loop. %This replaces all the loops in your processes, allowing you to use %procedures instead. loop     movement %move ONCE     coll            %draw ONCE     View.Update %put all of our drawing on screen (needed with offscreenonly) end loop

[Grim]

Using View.Update, I can't actually get Pac-Man to move. I get the drawing but nothing else.

[TheGuardian001]

Grim @ Thu Oct 21, 2010 9:34 pm wrote:

Using View.Update, I can't actually get Pac-Man to move. I get the drawing but nothing else.

1)Are you still using processes
2)Do you have both View.Set("offscreenonly") and View.Update? You need both.

[Grim]

TheGuardian001 @ 21/10/2010, 21:38 wrote:

Grim @ Thu Oct 21, 2010 9:34 pm wrote:

Using View.Update, I can't actually get Pac-Man to move. I get the drawing but nothing else.

1)Are you still using processes
2)Do you have both View.Set("offscreenonly") and View.Update? You need both.

Yes, using offscreenonly and View.Update, no processes. Here.

Turing:

View.Set ("graphics, nocursor, offscreenonly") var x : int := 100 var y : int := maxy - maxy div 2         % x and y of Pacman's centre var dx, dy : int                    % direction Pacman moves var mouth : int := 0                % size of mouth var dir : int := 0                  % mouth direction, 0=right, 90=up, etc. var xx : int := 0 var yy : int := 0 var collision : boolean := false var check : int := 1 const mup := chr (200) const mdown := chr (208) const mleft := chr (203) const mright := chr (205) dx := 1 dy := 0 procedure movement          var key : array char of boolean             xx := round (dx)             yy := round (dy)             Input.KeyDown (key)             if key (mup) then                 dir := 90                 dx := 0                 dy := 1             elsif key (mdown) then                 dir := 270                 dx := 0                 dy := -1             elsif key (mleft) then                 dir := 180                 dx := -1                 dy := 0             elsif key (mright) then                 dir := 0                 dx := 1                 dy := 0             end if end movement procedure coll         collision := false         mouth := mouth mod 45 + 1   % change size of the mouth         drawfillarc (x, y, 20, 20, mouth + dir, -mouth + dir, brightred)         delay (5)         drawfillarc (x, y, 20, 20, mouth + dir, -mouth + dir, white)         x := x + xx         y := y + yy         Draw.FillBox (0,0,1000,1000,black)         Draw.FillBox (20, 20, maxx - 20, maxy - 20, white)         Draw.FillBox (300, 0, 340, 150, black)         Draw.FillBox (300, 250, 340, 400, black)         if whatdotcolor (x, y) not= white then             x -= xx             y -= yy             collision := true         end if end coll loop movement coll View.Update end loop

Presumably, I could put View.Update at the end of each procedure, but even that doesn't work.

[TheGuardian001]

Let's take a look at the order you're drawing in:

code:

Draw pac man Erase pac man Draw Background Draw walls Update

You need to rearrange it so that Pac-Man is drawn last (since he's on top) and isn't erased before you update.

code:

Draw Background Draw Walls Draw Pac-Man Update

Erasing Pac-man is not actually required, since you draw a while box the size of the screen each loop anyway.