src/game/g_phys.pas

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