src/game/g_phys.pas

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