Dynamic in-game object creation and manipulation

[Tomi]

Hello User137!


My main problem the appearance of enemy's bullets, which happening at wrong place. Its may has to do with moving and deleting of the bullets?
I do it as follows:

if numofbullets>0 then
       begin
           i:=0;
           while i<numofbullets-1 do
           begin
            if bulletarray[i]<>nil then
            begin
                if (bulletarray[i].xplace>ClientWidth) or (bulletarray[i].xplace<1) or (bulletarray[i].yplace>ClientHeight) or (bulletarray[i].yplace<1) or (collwithplayer(bulletarray[i].xplace,bulletarray[i].yplace)=1) then
                begin
                    freeandnil(bulletarray[i]);
                    if i=numofbullets-1 then
                            dec(numofbullets)
                    else
                    begin
                            for j:=i+1 to numofbullets-1 do
                                bulletarray[j-1]:=bulletarray[j];
                            dec(numofbullets);
                            dec(i);
                    end;
                end else
                    begin
                     bulletarray[i].yplace:=bulletarray[i].yplace+4
                     MainWindow.Canvas.Draw(bulletarray[i].xplace,bulletarray[i].yplace,bulletarray[i].itsimage);
                    end;
            end;
            inc(i);
           end;
       end;

Maybe it is wrong?

[User137]

You don't have a semicolon at the end of

bulletarray[i].yplace:=bulletarray[i].yplace+4

And that's all i can see is wrong with the code. If you fire just 1 bullet, it starts from wrong place? Then it sounds like the mistake is the code that fires it.

[Tomi]

The player's bullets starts from right place, but the enemy's bullets sometimes comes from wrong places, as you can see in my program which can be download from 20th post.

[User137]

It's over 800 lines of code and not in english so it's difficult to read.

Here is something odd:

function TFoablak.pontirany(x1,y1,x2,y2: integer): word;
var szam: integer;
begin
    szam:=round(arctan2(y2-y1,x2-x1));
    if szam<0 then
            szam:=round(szam+2*pi);
    pontirany:=round(360-(szam*180)/pi);
end;

You should set szam: single; instead of integer, and not round it directly from arctan2(). There is too much precision lost for angle (if you have radians as integer there are only about 6 different angles in the whole 360 range.).

Also

if numofbullets>0 then  // < This line is not needed.
  begin
    i:=0;
    while i<numofbullets-1 do

Lets see what happens if numofbullets = 0:

i:=0;
    while 0<-1 do

0 is not < -1 so it never enters the while.