src/game/g_phys.pas

   1 {$MODE DELPHI}
   2 unit g_phys;
   3
   4 interface
   5
   6 uses
   7   e_graphics;
   8
   9 type
  10   PObj = ^TObj;
  11   TObj = record
  12     X, Y:    Integer;
  13     Rect:    TRectWH;
  14     Vel:     TPoint2i;
  15     Accel:   TPoint2i;
  16   end;
  17
  18 const
  19   MAX_YV = 30;
  20   LIMIT_VEL   = 16384;
  21   LIMIT_ACCEL = 1024;
  22
  23   MOVE_NONE       = 0;
  24   MOVE_HITWALL    = 1;
  25   MOVE_HITCEIL    = 2;
  26   MOVE_HITLAND    = 4;
  27   MOVE_FALLOUT    = 8;
  28   MOVE_INWATER    = 16;
  29   MOVE_HITWATER   = 32;
  30   MOVE_HITAIR     = 64;
  31   MOVE_BLOCK      = 128;
  32
  33 procedure g_Obj_Init(Obj: PObj);
  34 function  g_Obj_Move(Obj: PObj; Fallable: Boolean; Splash: Boolean; ClimbSlopes: Boolean = False): Word;
  35 function  g_Obj_Collide(Obj1, Obj2: PObj): Boolean; overload;
  36 function  g_Obj_Collide(X, Y: Integer; Width, Height: Word; Obj: PObj): Boolean; overload;
  37 function  g_Obj_CollidePoint(X, Y: Integer; Obj: PObj): Boolean;
  38 function  g_Obj_CollideLevel(Obj: PObj; XInc, YInc: Integer): Boolean;
  39 function  g_Obj_CollideStep(Obj: PObj; XInc, YInc: Integer): Boolean;
  40 function  g_Obj_CollideWater(Obj: PObj; XInc, YInc: Integer): Boolean;
  41 function  g_Obj_CollideLiquid(Obj: PObj; XInc, YInc: Integer): Boolean;
  42 function  g_Obj_CollidePanel(Obj: PObj; XInc, YInc: Integer; PanelType: Word): Boolean;
  43 function  g_Obj_StayOnStep(Obj: PObj): Boolean;
  44 procedure g_Obj_Push(Obj: PObj; VelX, VelY: Integer);
  45 procedure g_Obj_PushA(Obj: PObj; Vel: Integer; Angle: SmallInt);
  46 procedure g_Obj_SetSpeed(Obj: PObj; s: Integer);
  47 function  z_dec(a, b: Integer): Integer;
  48 function  z_fdec(a, b: Double): Double;
  49
  50 var
  51   gMon: Boolean = False;
  52
  53 implementation
  54
  55 uses
  56   g_map, g_basic, Math, g_player, g_console, SysUtils,
  57   g_sound, g_gfx, MAPDEF, g_monsters, g_game, BinEditor;
  58
  59 function g_Obj_StayOnStep(Obj: PObj): Boolean;
  60 begin
  61   Result := not g_Map_CollidePanel(Obj^.X+Obj^.Rect.X, Obj^.Y+Obj^.Rect.Y+Obj^.Rect.Height-1,
  62                                    Obj^.Rect.Width, 1,
  63                                    PANEL_STEP, False)
  64             and g_Map_CollidePanel(Obj^.X+Obj^.Rect.X, Obj^.Y+Obj^.Rect.Y+Obj^.Rect.Height,
  65                                    Obj^.Rect.Width, 1,
  66                                    PANEL_STEP, False);
  67 end;
  68
  69 function CollideLiquid(Obj: PObj; XInc, YInc: Integer): Boolean;
  70 begin
  71   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj^.Rect.Y+YInc,
  72                                Obj^.Rect.Width, Obj^.Rect.Height*2 div 3,
  73                                PANEL_WATER or PANEL_ACID1 or PANEL_ACID2, False);
  74 end;
  75
  76 function CollideLift(Obj: PObj; XInc, YInc: Integer): Integer;
  77 begin
  78   if g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj^.Rect.Y+YInc,
  79                         Obj^.Rect.Width, Obj^.Rect.Height,
  80                         PANEL_LIFTUP, False) then
  81     Result := -1
  82   else if g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj^.Rect.Y+YInc,
  83                           Obj^.Rect.Width, Obj^.Rect.Height,
  84                           PANEL_LIFTDOWN, False) then
  85     Result := 1
  86   else
  87     Result := 0;
  88 end;
  89
  90 function CollideHorLift(Obj: PObj; XInc, YInc: Integer): Integer;
  91 var
  92   left, right: Boolean;
  93 begin
  94   left := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj^.Rect.Y+YInc,
  95                              Obj^.Rect.Width, Obj^.Rect.Height,
  96                              PANEL_LIFTLEFT, False);
  97   right := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj^.Rect.Y+YInc,
  98                              Obj^.Rect.Width, Obj^.Rect.Height,
  99                              PANEL_LIFTRIGHT, False);
 100   if left and not right then
 101     Result := -1
 102   else if right and not left then
 103     Result := 1
 104   else
 105     Result := 0;
 106 end;
 107
 108 function CollidePlayers(_Obj: PObj; XInc, YInc: Integer): Boolean;
 109 var
 110   a: Integer;
 111 begin
 112   Result := False;
 113
 114   if gPlayers = nil then
 115     Exit;
 116
 117   for a := 0 to High(gPlayers) do
 118     if gPlayers[a] <> nil then
 119       with gPlayers[a] do
 120         if Live and
 121            g_Collide(GameX+PLAYER_RECT.X, GameY+PLAYER_RECT.Y,
 122                      PLAYER_RECT.Width, PLAYER_RECT.Height,
 123                      _Obj^.X+_Obj^.Rect.X+XInc, _Obj^.Y+_Obj^.Rect.Y+YInc,
 124                      _Obj^.Rect.Width, _Obj^.Rect.Height) then
 125         begin
 126           Result := True;
 127           Exit;
 128         end;
 129 end;
 130
 131 function CollideMonsters(Obj: PObj; XInc, YInc: Integer): Boolean;
 132 var
 133   a: Integer;
 134 begin
 135   Result := False;
 136
 137   if gMonsters = nil then
 138     Exit;
 139
 140   for a := 0 to High(gMonsters) do
 141     if gMonsters[a] <> nil then
 142       if gMonsters[a].Live and
 143          gMonsters[a].Collide(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj^.Rect.Y+YInc,
 144                               Obj^.Rect.Width, Obj^.Rect.Height) then
 145       begin
 146         Result := True;
 147         Exit;
 148       end;
 149 end;
 150
 151 function Blocked(Obj: PObj; XInc, YInc: Integer): Boolean;
 152 begin
 153   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj.Rect.Y+YInc,
 154                                Obj^.Rect.Width, Obj^.Rect.Height,
 155                                PANEL_BLOCKMON, False);
 156 end;
 157
 158 function g_Obj_CollideLevel(Obj: PObj; XInc, YInc: Integer): Boolean;
 159 begin
 160   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj.Rect.Y+YInc,
 161                                Obj^.Rect.Width, Obj^.Rect.Height,
 162                                PANEL_WALL, False);
 163 end;
 164
 165 function g_Obj_CollideStep(Obj: PObj; XInc, YInc: Integer): Boolean;
 166 begin
 167   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj.Rect.Y+YInc,
 168                                Obj^.Rect.Width, Obj^.Rect.Height,
 169                                PANEL_STEP, False);
 170 end;
 171
 172 function g_Obj_CollideWater(Obj: PObj; XInc, YInc: Integer): Boolean;
 173 begin
 174   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj.Rect.Y+YInc,
 175                                Obj^.Rect.Width, Obj^.Rect.Height,
 176                                PANEL_WATER, False);
 177 end;
 178
 179 function g_Obj_CollideLiquid(Obj: PObj; XInc, YInc: Integer): Boolean;
 180 begin
 181   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj.Rect.Y+YInc,
 182                                Obj^.Rect.Width, Obj^.Rect.Height,
 183                                PANEL_WATER or PANEL_ACID1 or PANEL_ACID2, False);
 184 end;
 185
 186 function g_Obj_CollidePanel(Obj: PObj; XInc, YInc: Integer; PanelType: Word): Boolean;
 187 begin
 188   Result := g_Map_CollidePanel(Obj^.X+Obj^.Rect.X+XInc, Obj^.Y+Obj.Rect.Y+YInc,
 189                                Obj^.Rect.Width, Obj^.Rect.Height,
 190                                PanelType, False);
 191 end;
 192
 193 procedure g_Obj_Splash(Obj: PObj; Color: Byte);
 194 var
 195   MaxVel: Integer;
 196 begin
 197   MaxVel := Max(Abs(Obj^.Vel.X), Abs(Obj^.Vel.Y));
 198   if MaxVel > 4 then begin
 199     if MaxVel < 10 then
 200       g_Sound_PlayExAt('SOUND_GAME_BULK1', Obj^.X, Obj^.Y)
 201     else
 202       g_Sound_PlayExAt('SOUND_GAME_BULK2', Obj^.X, Obj^.Y);
 203   end;
 204
 205   g_GFX_Water(Obj^.X+Obj^.Rect.X+(Obj^.Rect.Width div 2),
 206               Obj^.Y+Obj^.Rect.Y+(Obj^.Rect.Height div 2),
 207               Min(5*(Abs(Obj^.Vel.X)+Abs(Obj^.Vel.Y)), 50),
 208               -Obj^.Vel.X, -Obj^.Vel.Y,
 209               Obj^.Rect.Width, 16, Color);
 210 end;
 211
 212 function move(Obj: PObj; dx, dy: Integer; ClimbSlopes: Boolean): Word;
 213 var
 214   i: Integer;
 215   sx, sy: ShortInt;
 216   st: Word;
 217
 218   procedure slope(s: Integer);
 219   var
 220     i: Integer;
 221   begin
 222     i := 0;
 223     while g_Obj_CollideLevel(Obj, sx, 0) and (i < 4) do
 224     begin
 225       Obj^.Y := Obj^.Y + s;
 226       Inc(i);
 227     end;
 228     Obj^.X := Obj^.X + sx;
 229   end;
 230
 231   function movex(): Boolean;
 232   begin
 233     Result := False;
 234
 235   // Åñëè ìîíñòðó øàãíóòü â ñòîðîíó, à òàì áëîêìîí:
 236     if gMon and not WordBool(st and MOVE_BLOCK) then
 237       if Blocked(Obj, sx, 0) then
 238         st := st or MOVE_BLOCK;
 239
 240   // Åñëè øàãíóòü â ñòîðîíó, à òàì ñòåíà => øàãàòü íåëüçÿ:
 241     if g_Obj_CollideLevel(Obj, sx, 0) then
 242       begin
 243         if ClimbSlopes and (Abs(dy) < 2) then
 244           begin
 245             Result := True;
 246             if (not g_Obj_CollideLevel(Obj, sx, -12)) // çàáèðàåìñÿ íà 12 ïèêñåëåé âëåâî/âïðàâî
 247             and g_Obj_CollidePanel(Obj, 0, 1, PANEL_WALL or PANEL_STEP) // òîëüêî åñëè åñòü çåìëÿ ïîä íîãàìè
 248             then
 249               slope(-1)
 250             else
 251               begin
 252                 Result := False;
 253                 st := st or MOVE_HITWALL;
 254               end;
 255           end
 256           else
 257             st := st or MOVE_HITWALL;
 258       end
 259     else // Òàì ñòåíû íåò
 260       begin
 261         if CollideLiquid(Obj, sx, 0) then
 262           begin // Åñëè øàãíóòü â ñòîðîíó, à òàì òåïåðü æèäêîñòü
 263             if not WordBool(st and MOVE_INWATER) then
 264               st := st or MOVE_HITWATER;
 265           end
 266         else // Åñëè øàãíóòü â ñòîðîíó, à òàì óæå íåò æèäêîñòè
 267           if WordBool(st and MOVE_INWATER) then
 268             st := st or MOVE_HITAIR;
 269
 270       // Øàã:
 271         Obj^.X := Obj^.X + sx;
 272         Result := True;
 273       end;
 274   end;
 275
 276   function movey(): Boolean;
 277   begin
 278     Result := False;
 279
 280   // Åñëè ìîíñòðó øàãíóòü ïî âåðòèêàëè, à òàì áëîêìîí:
 281     if gMon and not WordBool(st and MOVE_BLOCK) then
 282       if Blocked(Obj, 0, sy) then
 283         st := st or MOVE_BLOCK;
 284
 285   // Åñëè øàãíóòü â ïî âåðòèêàëè, à òàì ñòåíà => øàãàòü íåëüçÿ:
 286   // Èëè åñëè øàãíóòü âíèç, à òàì ñòóïåíü => øàãàòü íåëüçÿ:
 287     if g_Obj_CollideLevel(Obj, 0, sy) or
 288        ((sy > 0) and g_Obj_StayOnStep(Obj)) then
 289       begin
 290         if sy > 0 then
 291           st := st or MOVE_HITLAND
 292         else
 293           st := st or MOVE_HITCEIL;
 294       end
 295     else // Òàì ñòåíû íåò. È ñòóïåíè ñíèçó òîæå íåò
 296       begin
 297         if CollideLiquid(Obj, 0, sy) then
 298           begin // Åñëè øàãíóòü â ïî âåðòèêàëè, à òàì òåïåðü æèäêîñòü
 299             if not WordBool(st and MOVE_INWATER) then
 300               st := st or MOVE_HITWATER;
 301           end
 302         else // Åñëè øàãíóòü â ïî âåðòèêàëè, à òàì óæå íåò æèäêîñòè
 303           if WordBool(st and MOVE_INWATER) then
 304             st := st or MOVE_HITAIR;
 305
 306       // Øàã:
 307         Obj^.Y := Obj^.Y + sy;
 308
 309         Result := True;
 310       end;
 311   end;
 312
 313 begin
 314   st := MOVE_NONE;
 315
 316 // Îáúåêò â æèäêîñòè:
 317   if CollideLiquid(Obj, 0, 0) then
 318     st := st or MOVE_INWATER;
 319
 320 // Ìîíñòð â áëîêìîíå:
 321   if gMon then
 322     if Blocked(Obj, 0, 0) then
 323       st := st or MOVE_BLOCK;
 324
 325 // Äâèãàòüñÿ íå íàäî:
 326   if (dx = 0) and (dy = 0) then
 327   begin
 328     Result := st;
 329     Exit;
 330   end;
 331
 332   sx := g_basic.Sign(dx);
 333   sy := g_basic.Sign(dy);
 334   dx := Abs(dx);
 335   dy := Abs(dy);
 336
 337   for i := 1 to dx do
 338     if not movex() then
 339       Break;
 340
 341   for i := 1 to dy do
 342     if not movey() then
 343       Break;
 344
 345   Result := st;
 346 end;
 347
 348 procedure g_Obj_Init(Obj: PObj);
 349 begin
 350   ZeroMemory(Obj, SizeOf(TObj));
 351 end;
 352
 353 function g_Obj_Move(Obj: PObj; Fallable: Boolean; Splash: Boolean; ClimbSlopes: Boolean = False): Word;
 354 var
 355   xv, yv, dx, dy: Integer;
 356   inwater: Boolean;
 357   c: Boolean;
 358   wtx: DWORD;
 359 label
 360   _move;
 361 begin
 362 // Ëèìèòû íà ñêîðîñòü è óñêîðåíèå
 363   if      Obj^.Vel.X < -LIMIT_VEL then Obj^.Vel.X := -LIMIT_VEL
 364   else if Obj^.Vel.X >  LIMIT_VEL then Obj^.Vel.X :=  LIMIT_VEL;
 365   if      Obj^.Vel.Y < -LIMIT_VEL then Obj^.Vel.Y := -LIMIT_VEL
 366   else if Obj^.Vel.Y >  LIMIT_VEL then Obj^.Vel.Y :=  LIMIT_VEL;
 367   if      Obj^.Accel.X < -LIMIT_ACCEL then Obj^.Accel.X := -LIMIT_ACCEL
 368   else if Obj^.Accel.X >  LIMIT_ACCEL then Obj^.Accel.X :=  LIMIT_ACCEL;
 369   if      Obj^.Accel.Y < -LIMIT_ACCEL then Obj^.Accel.Y := -LIMIT_ACCEL
 370   else if Obj^.Accel.Y >  LIMIT_ACCEL then Obj^.Accel.Y :=  LIMIT_ACCEL;
 371
 372 // Âûëåòåë çà íèæíþþ ãðàíèöó êàðòû:
 373   if Obj^.Y > gMapInfo.Height+128 then
 374   begin
 375     Result := MOVE_FALLOUT;
 376     Exit;
 377   end;
 378
 379 // Ìåíÿåì ñêîðîñòü è óñêîðåíèå òîëüêî ïî ÷åòíûì êàäðàì:
 380   c := gTime mod (GAME_TICK*2) <> 0;
 381
 382   if c then
 383     goto _move;
 384
 385   case CollideLift(Obj, 0, 0) of
 386     -1: //up
 387       begin
 388         Obj^.Vel.Y := Obj^.Vel.Y - 1; // Ëèôò ââåðõ
 389         if Obj^.Vel.Y < -5 then
 390           Obj^.Vel.Y := Obj^.Vel.Y + 1;
 391       end;
 392
 393     1: //down
 394       begin
 395         if Obj^.Vel.Y > 5 then
 396           Obj^.Vel.Y := Obj^.Vel.Y - 1;
 397         Obj^.Vel.Y := Obj^.Vel.Y + 1; // Ãðàâèòàöèÿ èëè ëèôò âíèç
 398       end;
 399
 400     0:
 401       begin
 402         if Fallable then
 403           Obj^.Vel.Y := Obj^.Vel.Y + 1; // Ãðàâèòàöèÿ
 404         if Obj^.Vel.Y > MAX_YV then
 405           Obj^.Vel.Y := Obj^.Vel.Y - 1;
 406       end;
 407   end;
 408
 409   case CollideHorLift(Obj, 0, 0) of
 410     -1: //left
 411       begin
 412         Obj^.Vel.X := Obj^.Vel.X - 3; // Ëèôò ââåðõ
 413         if Obj^.Vel.X < -9 then
 414           Obj^.Vel.X := Obj^.Vel.X + 3;
 415       end;
 416
 417     1: //right
 418       begin
 419         Obj^.Vel.X := Obj^.Vel.X + 3;
 420         if Obj^.Vel.X > 9 then
 421           Obj^.Vel.X := Obj^.Vel.X - 3;
 422       end;
 423     // 0 is not needed here
 424   end;
 425
 426   inwater := CollideLiquid(Obj, 0, 0);
 427   if inwater then
 428   begin
 429     xv := Abs(Obj^.Vel.X)+1;
 430     if xv > 5 then
 431       Obj^.Vel.X := z_dec(Obj^.Vel.X, (xv div 2)-2);
 432
 433     yv := Abs(Obj^.Vel.Y)+1;
 434     if yv > 5 then
 435       Obj^.Vel.Y := z_dec(Obj^.Vel.Y, (yv div 2)-2);
 436
 437     xv := Abs(Obj^.Accel.X)+1;
 438     if xv > 5 then
 439       Obj^.Accel.X := z_dec(Obj^.Accel.X, (xv div 2)-2);
 440
 441     yv := Abs(Obj^.Accel.Y)+1;
 442     if yv > 5 then
 443       Obj^.Accel.Y := z_dec(Obj^.Accel.Y, (yv div 2)-2);
 444   end;
 445
 446 // Óìåíüøàåì ïðèáàâêó ê ñêîðîñòè:
 447   Obj^.Accel.X := z_dec(Obj^.Accel.X, 1);
 448   Obj^.Accel.Y := z_dec(Obj^.Accel.Y, 1);
 449
 450 _move:
 451
 452   xv := Obj^.Vel.X + Obj^.Accel.X;
 453   yv := Obj^.Vel.Y + Obj^.Accel.Y;
 454
 455   dx := xv;
 456   dy := yv;
 457
 458   Result := move(Obj, dx, dy, ClimbSlopes);
 459
 460 // Áðûçãè (åñëè íóæíû):
 461   if Splash then
 462     if WordBool(Result and MOVE_HITWATER) then
 463     begin
 464       wtx := g_Map_CollideLiquid_Texture(Obj^.X+Obj^.Rect.X,
 465                                          Obj^.Y+Obj^.Rect.Y,
 466                                          Obj^.Rect.Width,
 467                                          Obj^.Rect.Height*2 div 3);
 468       case wtx of
 469         TEXTURE_SPECIAL_WATER:
 470           g_Obj_Splash(Obj, 3);
 471         TEXTURE_SPECIAL_ACID1:
 472           g_Obj_Splash(Obj, 2);
 473         TEXTURE_SPECIAL_ACID2:
 474           g_Obj_Splash(Obj, 1);
 475         TEXTURE_NONE:
 476           ;
 477         else
 478           g_Obj_Splash(Obj, 0);
 479       end;
 480     end;
 481
 482 // Ìåíÿåì ñêîðîñòü è óñêîðåíèå òîëüêî ïî ÷åòíûì êàäðàì:
 483   if c then
 484     Exit;
 485
 486 // Âðåçàëèñü â ñòåíó - ñòîï:
 487   if WordBool(Result and MOVE_HITWALL) then
 488   begin
 489     Obj^.Vel.X := 0;
 490     Obj^.Accel.X := 0;
 491   end;
 492
 493 // Âðåçàëèñü â ïîë èëè ïîòîëîê - ñòîï:
 494   if WordBool(Result and (MOVE_HITCEIL or MOVE_HITLAND)) then
 495   begin
 496     Obj^.Vel.Y := 0;
 497     Obj^.Accel.Y := 0;
 498   end;
 499 end;
 500
 501 function g_Obj_Collide(Obj1, Obj2: PObj): Boolean;
 502 begin
 503   Result := g_Collide(Obj1^.X+Obj1^.Rect.X, Obj1^.Y+Obj1^.Rect.Y,
 504                       Obj1^.Rect.Width, Obj1^.Rect.Height,
 505                       Obj2^.X+Obj2^.Rect.X, Obj2^.Y+Obj2^.Rect.Y,
 506                       Obj2^.Rect.Width, Obj2^.Rect.Height);
 507 end;
 508
 509 function g_Obj_Collide(X, Y: Integer; Width, Height: Word; Obj: PObj): Boolean;
 510 begin
 511   Result := g_Collide(X, Y,
 512                       Width, Height,
 513                       Obj^.X+Obj^.Rect.X, Obj^.Y+Obj^.Rect.Y,
 514                       Obj^.Rect.Width, Obj^.Rect.Height);
 515 end;
 516
 517 function g_Obj_CollidePoint(X, Y: Integer; Obj: PObj): Boolean;
 518 begin
 519   Result := g_CollidePoint(X, Y, Obj^.X+Obj^.Rect.X, Obj^.Y+Obj^.Rect.Y,
 520                            Obj^.Rect.Width, Obj^.Rect.Height);
 521 end;
 522
 523 procedure g_Obj_Push(Obj: PObj; VelX, VelY: Integer);
 524 begin
 525   Obj^.Vel.X := Obj^.Vel.X + VelX;
 526   Obj^.Vel.Y := Obj^.Vel.Y + VelY;
 527 end;
 528
 529 procedure g_Obj_PushA(Obj: PObj; Vel: Integer; Angle: SmallInt);
 530 var
 531   s, c: Extended;
 532
 533 begin
 534   SinCos(DegToRad(-Angle), s, c);
 535
 536   Obj^.Vel.X := Obj^.Vel.X + Round(Vel*c);
 537   Obj^.Vel.Y := Obj^.Vel.Y + Round(Vel*s);
 538 end;
 539
 540 procedure g_Obj_SetSpeed(Obj: PObj; s: Integer);
 541 var
 542   m, vx, vy: Integer;
 543 begin
 544   vx := Obj^.Vel.X;
 545   vy := Obj^.Vel.Y;
 546
 547   m := Max(Abs(vx), Abs(vy));
 548   if m = 0 then
 549     m := 1;
 550
 551   Obj^.Vel.X := (vx*s) div m;
 552   Obj^.Vel.Y := (vy*s) div m;
 553 end;
 554
 555 function z_dec(a, b: Integer): Integer;
 556 begin
 557 // Ïðèáëèæàåì a ê 0 íà b åäèíèö:
 558   if Abs(a) < b then
 559     Result := 0
 560   else
 561     if a > 0 then
 562       Result := a - b
 563     else
 564       if a < 0 then
 565         Result := a + b
 566       else // a = 0
 567         Result := 0;
 568 end;
 569
 570 function z_fdec(a, b: Double): Double;
 571 begin
 572 // Ïðèáëèæàåì a ê 0.0 íà b åäèíèö:
 573   if Abs(a) < b then
 574     Result := 0.0
 575   else
 576     if a > 0.0 then
 577       Result := a - b
 578     else
 579       if a < 0.0 then
 580         Result := a + b
 581       else // a = 0.0
 582         Result := 0.0;
 583 end;
 584
 585 end.