Collission detection on level ( source Travels doc + some other examples)

[robert83]

Hello everyone,

This weekend I've managed to get a bit further on my road to making some platform games in the future...

Anyway using Traveler's guide for platform game + some andorra 2d examples... I've managed to create a simple level , load it, and my hero ( the big bad red block ) can move around and hits the wall... only problem is I dunno why, but sometimes he does not exactly hits it but stops a bit earlier...

I'm including my complete source + attached the zipped program so you can see what I mean, I've tried to implement my own method of detecting the edges, by defining the 4 points of the block, not much different from the original guide, but I understand this one atleast ...

unit Main;
interface
uses
  Windows,Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, AdDraws, AdClasses, AdTypes, AdPerformanceCounter, AdDevIL,AdSprites;
  type
  //Types that are used to tell the character which key has been pressed
  TKey = (kyUp, kyDown, kyLeft, kyRight);
  TKeys = set of TKey;
  TTileInfo = Record
  tilenr : integer;
  end;
  TPlatform = class(TImageSprite)
    private
    protected
      procedure DoMove(TimeGap: Double); override;
      procedure DoCollision(Sprite:TSprite; var Done:boolean); override;
    public
      constructor Create(AParent:TSprite);override;
    end;
  TBlurp = class(TImageSprite)
    private
    FKeys:TKeys;
    X_Direction:double;
    Y_Direction:double;
    isfalling:boolean;
    iswall:boolean;
    protected
      procedure DoMove(TimeGap: Double);override;
      procedure DoCollision(Sprite:TSprite; var Done:boolean);override;
    public
      constructor Create(AParent:Tsprite);override;
      procedure SetKeys(Keys:TKeys);
      function testForWall(spriteXpos,spriteYpos:single;spriteWidth,spriteHeight:integer):boolean;
    end;
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormKeyDown(Sender: TObject; var Key: Word;
      Shift: TShiftState);
  private
    { Private declarations }
  public
    { Public declarations }
    AdDraw:TAdDraw;
    AdSpriteEngine:TSpriteEngine;
    AdImageList:TAdImageList;
    AdPerCounter:TAdPerformanceCounter;
    AdPixelCollisionTester: TAdSpritePixelCollisionTester;
    Blurp:TBlurp;
    procedure Idle(Sender:TObject; var Done:boolean);
    procedure LoadLevel;
  end;
var
  Form1: TForm1;
  TileInfo : array [1..39, 0..28 ] of TTileInfo;
  ActTime : double;
implementation
{$R *.dfm}
procedure TForm1.LoadLevel;
var
  level:TStringList;
  ax,ay:integer;
begin
  level := TStringList.Create;
  level.LoadFromFile(ExtractFilePath(Application.ExeName)+'level2.txt');
  for ay := 0 to level.Count-1  do
  begin
    for ax := 1 to length(level[ay]) do
    begin
      case level[ay][ax] of
        'x':
        begin
          TileInfo[ax,ay].tilenr:=1;
          with TPlatform.Create(AdSpriteEngine) do
          begin
            Image := AdImageList.Find('Kocka');
            x := ax*64;
            y := ay*64;
            z := 0;
          end;
        end;
        'X':
        begin
          TileInfo[ax,ay].tilenr:=1;
          with TPlatForm.Create(AdSpriteEngine) do
          begin
            Image := AdImageList.Find('Kocka2');
            x := ax*64;
            y := ay*64;
            z := 0;
          end;
        end;
        '-': TileInfo[ax,ay].tilenr:=2;
      end;
    end;
  end;
  level.Free;
end;
procedure TBlurp.SetKeys(Keys: TKeys);
begin
  if Keys = FKeys then exit;
  FKeys := Keys;
  if kyRight in Keys then x_direction:=1.5;
  if kyLeft in Keys then x_direction:=-1.5;
  if kyUp in Keys then y_direction:=-1.5;
  if kyDown in Keys then y_direction:=1.5;
  if Keys = [] then
    begin
      x_direction:=0;
      y_direction:=0;
    end;
end;
 
constructor TPlatform.Create(AParent: TSprite);
begin
  inherited;
end;
constructor TBlurp.Create(AParent: TSprite);
begin
  inherited;
end;
 
procedure TBlurp.DoMove(TimeGap: Double);
begin
  inherited;
 { X:=X+X_direction;
  Y:=Y+Y_direction; }
 
 { if X <= 0 then X:=0;
  if X > 640-Image.Width then X:=640-Image.Width;
  if Y < 0 then Y:=0;
  if Y > 480-Image.Height then Y:=480-Image.Height; }
  Collision;
end;
function TBlurp.testForWall(spriteXpos,spriteYpos:single;spriteWidth,spriteHeight:integer):boolean;
begin
  testForWall := false;
  if not (TileInfo[round(spriteXpos) div 64, round(spriteYpos) div 64].tilenr in [2]) or not
  (TileInfo[(round(spriteXpos)+spriteWidth) div 64, round(spriteYpos) div 64].tilenr in [2]) or not
  (TileInfo[round(spriteXpos)div 64, (round(spriteYpos)+spriteHeight) div 64].tilenr in [2]) or not
  (TileInfo[(round(spriteXpos)+spriteWidth) div 64, (round(spriteYpos)+spriteHeight) div 64].tilenr in [2]) then testForWall :=true;
end;
procedure TPlatform.DoMove(TimeGap : Double);
begin
  inherited;
  Collision;
end;
 
procedure TBlurp.DoCollision(Sprite:TSprite; var Done:boolean);
begin
  if Sprite is TPlatform then
    begin
      isFalling:=false;
    end;
end;
procedure TPlatform.DoCollision(Sprite:TSprite; var Done:boolean);
begin
end;
 
 
procedure TForm1.FormCreate(Sender: TObject);
var i: integer;
begin
  AdPerCounter := TAdPerformanceCounter.Create;
  AdDraw := TAdDraw.Create(self);
  AdDraw.DllName := 'AndorraDX93D.dll';
 with AdDraw.Display do
    begin
    {  Width := 640;
      Height := 480;
      BitDepth := ad16Bit; //The colour depth. The values "ad16Bit" and "ad32Bit" are allowed here.
      DisplayMode := dmFullscreen; }
    end;
 
if AdDraw.Initialize then
  begin
    Application.OnIdle := Idle;
    AdImageList := TAdImageList.Create(AdDraw);
    AdImageList.LoadFromFile('BackGround.ail');
 
    //create the SpriteEngine
     AdSpriteEngine := TSpriteEngine.Create(nil);
     AdSpriteEngine.Surface := AdDraw;
    //Create the collision tester
    AdPixelCollisionTester := TAdSpritePixelCollisionTester.Create(AdDraw);
    LoadLevel;
    //create TImageSprite
    Randomize;
        Blurp := TBlurp.Create(AdSpriteEngine);
        with Blurp.Create(AdSpriteEngine) do
          begin
            Image := AdImageList.Find('Hero');
            X := 128;
            Y := 128;
            Z := 0;
            CollisionTester := AdPixelCollisionTester;
            SetKeys([]);
            isfalling:=true;
          end;
 
 
    // ************* hater *********************************
  end
 else
  begin
     ShowMessage('Error while initializing Andorra 2D. Try to use another display'+
               'mode or use another video adapter.');
    halt; //<-- Completely shuts down the application
  end;
end;
procedure TForm1.Idle(Sender: TObject; var Done: boolean);
var keys: TKeys;
 begin
   if AdDraw.CanDraw then // Only continue, if drawing is possible
   begin
    AdPerCounter.Calculate;
    AdPerCounter.MaximumFrameRate:=60;
 
    AdDraw.ClearSurface(clBlack); // Fill the surface with black color
    AdDraw.BeginScene;
    // Here you need to perform all drawing operations later
    ActTime := ActTime + AdPerCounter.TimeGap;
    if ActTime > 25 then
    begin
         keys := [];
          if GetKeyState(VK_LEFT) < 0 then
            begin
              if not Blurp.testForWall(Blurp.X-3,Blurp.Y,Blurp.Image.Width,Blurp.Image.Height) then
                begin
                  Blurp.X:=Blurp.X-3;
                  AdSpriteEngine.X:=AdSpriteEngine.X+3;
                end;
            end;
          if GetKeyState(VK_RIGHT) < 0 then
            begin
              if not Blurp.testForWall(Blurp.X+3,Blurp.Y,Blurp.Image.Width,Blurp.Image.Height) then
                begin
                  Blurp.X:=Blurp.X+3;
                  AdSpriteEngine.X:=AdSpriteEngine.X-3;
                end;
            end;
          if GetKeyState(VK_UP) < 0 then
            begin
              if not Blurp.testForWall(Blurp.X,Blurp.Y-3,Blurp.Image.Width,Blurp.Image.Height) then
                begin
                  Blurp.Y:=Blurp.Y-3;
                  AdSpriteEngine.Y:=AdSpriteEngine.Y+3;
                end;
            end;
          if GetKeyState(VK_DOWN) < 0 then
            begin
              if not Blurp.testForWall(Blurp.X,Blurp.Y+3,Blurp.Image.Width,Blurp.Image.Height) then
                begin
                  Blurp.Y:=Blurp.Y+3;
                  AdSpriteEngine.Y:=AdSpriteEngine.Y-3;
                end;
            end;
          Blurp.SetKeys(Keys);
      ActTime := 0;
    end;
   { if Blurp.isfalling = true then
      begin
        Blurp.Y:=Blurp.Y+1;
      end;
    Blurp.isfalling:=true;}
 
    AdSpriteEngine.Draw;
    AdSpriteEngine.Move(25/1000);
    AdSpriteEngine.Dead;
    // debug
    AdDraw.Canvas.Textout(0,40,'Ido: '+inttostr(TileInfo[1,1].tilenr));
//    AdDraw.Canvas.TextOut(0,80,'Player Collision:' +Blurp.testForWall(Blurp.X,Blurp.Y,Blurp.Image.Width,Blurp.Image.Height));
 
 
    AdDraw.EndScene;
    AdDraw.Flip; // Draws you result on the screen. Otherwise, you would not see anything
   end;
  Done := false; // Important, otherwise the function will not be called in every loop
 end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
   AdSpriteEngine.Free;
   AdImageList.Free;
   AdPerCounter.Free;
   AdDraw.Free;
end;
procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  if Key = VK_ESCAPE then Close;
end;
end.

this worked :

   function TOurSprite.testForWall(spriteXpos,spriteYpos:single; 
              spriteWidth,spriteHeight:integer):boolean;
begin
    testForWall := false;
  //test topside
  if not (TileInfo[((round(spriteXpos)+spriteWidth) div 32),
        (round(spriteYpos) div 32)].tilenr in [6,7,100])
  //test bottomside
  or not ((TileInfo[((round(spriteXpos)+spriteWidth) div 32),
        ((round(spriteYpos)+spriteHeight) div 32)].tilenr in [6,7,100])
     and (TileInfo[(round(spriteXpos) div 32),
        ((round(spriteYpos)+spriteHeight) div 32)].tilenr in [6,7,100]))
  then testForWall := true;

only thing was I was not able to figure it out how and why I was able to figure out that
it was checking , these coordinates in this order

X------1
| -------|
3------2 Why was it not checking 4 x,y have no idea... it worked... but I did not want to use
something I don't understand...

Anyway back to my way I defined all 4 points
X----X
| ------|
X----X

only problem is sometimes my Hero Character stops a bit earlier then it should...
I must stop him a bit sooner otherwise... I get wallhit true...and cannot move in any direction...

Please help me out a bit here ( I try to do as much as possible by myself...but I'm really stuck here...)

Egyszeru 5 figura maga.zip

Greetings

Robert

[paul_nicholls]

Maybe this site can help?
http://www.tonypa.pri.ee/tbw/tut05.html

It is using action script (Flash) but I managed to folow the tutorials, especially "Hit the Wall" and "Jumping" to make a simple platform game with collision that worked quite well

cheers,
Paul

[User137]

function TBlurp.testForWall(spriteXpos,spriteYpos:single;spriteWidth,spriteHeight:integer):boolean;
begin
  testForWall := false;
  if not (TileInfo[round(spriteXpos) div 64, round(spriteYpos) div 64].tilenr in [2]) or not
  (TileInfo[(round(spriteXpos)+spriteWidth) div 64, round(spriteYpos) div 64].tilenr in [2]) or not
  (TileInfo[round(spriteXpos)div 64, (round(spriteYpos)+spriteHeight) div 64].tilenr in [2]) or not
  (TileInfo[(round(spriteXpos)+spriteWidth) div 64, (round(spriteYpos)+spriteHeight) div 64].tilenr in [2]) then testForWall :=true;
end;

Test with changing round() to trunc(). There is a difference in how they work, and tiles are usually drawn from their top left corner, not from middle.

[robert83]

Hi,

same thing with Trunc...

I don't get this : "and tiles are usually drawn from their top left corner, not from middle."
- why did you write this ? am I doing something wrong when checking the 4 corners?

By the way... if I use it like this :

 if not Blurp.testForWall(Blurp.X,Blurp.Y,Blurp.Image.Width,Blurp.Image.Height) then

for any direction... it stops when it hits the wall... but since it HIT the wall I can no longer
move in any direction... that is why I did that -3 here +3 here... I'm a bit confused there... I should check if after the next step there is a wall...

Greetings
Rob

[Traveler]

There are two ways to counter the-getting-stuck-in-the-wall problem.

1) Move away from the wall when you're inside it. (the preferred method)
For example, you're moving to the left at 3 pixel/cycle. You're going to hit the wall in 11px. Meaning you'll end up in the wall (and get stuck) in 4 cycles. At the fourth cycle your position is 1px inside the wall, so you correct that by setting the sprite position 2 pixels back.

2) Change the testwall function to include the direction. Meaning when you go to the right you only test if the right side of your sprite is inside a wall. If you're going left, only test if you with with the left part. This way you can still move if one side of your sprite is inside a wall.

[paul_nicholls]

The tutorial site I posted seems to do the testing like this:

find new object position (position + velocity).
if edge inside a wall
  move object so it touches edge of wall 
else 
  do full movement in that direction

Oh, and it breaks up the movement and does it vertically then horizontally (or is it the other way around...I forget LOL)

I hope this helps

cheers,
Paul