X-Git-Url: https://deadsoftware.ru/gitweb?a=blobdiff_plain;f=src%2Fgame%2Fg_grid.pas;h=049868c7821e7784afa08dbe18e68ab97c0d6a31;hb=a0b4df67e96c6b5e55e95269a87975df67692e6b;hp=882ef3a4504ac3cfae567a8b9906c084065a825a;hpb=660ceacb88bb8e92cfebe05698369e6a6904751c;p=d2df-sdl.git

diff --git a/src/game/g_grid.pas b/src/game/g_grid.pas
index 882ef3a..049868c 100644
--- a/src/game/g_grid.pas
+++ b/src/game/g_grid.pas
@@ -20,7 +20,7 @@
   {.$DEFINE D2F_DEBUG_XXQ}
   {.$DEFINE D2F_DEBUG_MOVER}
 {$ENDIF}
-{.$DEFINE GRID_USE_ORTHO_ACCEL}
+{$DEFINE GRID_USE_ORTHO_ACCEL}
 unit g_grid;
 
 interface
@@ -33,7 +33,6 @@ type
   public
     type TGridQueryCB = function (obj: ITP; tag: Integer): Boolean is nested; // return `true` to stop
     type TGridRayQueryCB = function (obj: ITP; tag: Integer; x, y, prevx, prevy: Integer): Boolean is nested; // return `true` to stop
-    type TGridAlongQueryCB = function (obj: ITP; tag: Integer): Boolean is nested; // return `true` to stop
 
     type TCellQueryCB = procedure (x, y: Integer) is nested; // top-left cell corner coords
 
@@ -45,7 +44,7 @@ type
       GridDefaultTileSize = 32; // must be power of two!
       GridCellBucketSize = 8; // WARNING! can't be less than 2!
 
-  private
+  public
     type
       PBodyProxyRec = ^TBodyProxyRec;
       TBodyProxyRec = record
@@ -58,28 +57,69 @@ type
 
       private
         procedure setup (aX, aY, aWidth, aHeight: Integer; aObj: ITP; aTag: Integer);
+
+        function getTag (): Integer; inline;
+        procedure setTag (v: Integer); inline;
+
+        function getEnabled (): Boolean; inline;
+        procedure setEnabled (v: Boolean); inline;
+
+        function getX1 (): Integer; inline;
+        function getY1 (): Integer; inline;
+
+      public
+        property x: Integer read mX;
+        property y: Integer read mY;
+        property width: Integer read mWidth;
+        property height: Integer read mHeight;
+        property tag: Integer read getTag write setTag;
+        property enabled: Boolean read getEnabled write setEnabled;
+        property obj: ITP read mObj;
+
+        property x0: Integer read mX;
+        property y0: Integer read mY;
+        property x1: Integer read getX1;
+        property y1: Integer read getY1;
       end;
 
+  private
+    type
       PGridCell = ^TGridCell;
       TGridCell = record
         bodies: array [0..GridCellBucketSize-1] of Integer; // -1: end of list
         next: Integer; // in this cell; index in mCells
       end;
 
+      TCellArray = array of TGridCell;
+
       TGridInternalCB = function (grida: Integer; bodyId: TBodyProxyId): Boolean of object; // return `true` to stop
 
   private
     //mTileSize: Integer;
     const mTileSize = GridDefaultTileSize;
+    type TGetProxyFn = function (pxidx: Integer): PBodyProxyRec of object;
 
   public
     const tileSize = mTileSize;
 
+    type
+      TAtPointEnumerator = record
+      private
+        mCells: TCellArray;
+        curidx, curbki: Integer;
+        getpx: TGetProxyFn;
+      public
+        constructor Create (acells: TCellArray; aidx: Integer; agetpx: TGetProxyFn);
+        function MoveNext (): Boolean; inline;
+        function getCurrent (): PBodyProxyRec; inline;
+        property Current: PBodyProxyRec read getCurrent;
+      end;
+
   private
     mMinX, mMinY: Integer; // so grids can start at any origin
     mWidth, mHeight: Integer; // in tiles
     mGrid: array of Integer; // mWidth*mHeight, index in mCells
-    mCells: array of TGridCell; // cell pool
+    mCells: TCellArray; // cell pool
     mFreeCell: Integer; // first free cell index or -1
     mLastQuery: LongWord;
     mUsedCells: Integer;
@@ -87,6 +127,7 @@ type
     mProxyFree: TBodyProxyId; // free
     mProxyCount: Integer; // currently used
     mProxyMaxCount: Integer;
+    mInQuery: Boolean;
 
   public
     dbgShowTraceLog: Boolean;
@@ -115,6 +156,8 @@ type
     function getGridWidthPx (): Integer; inline;
     function getGridHeightPx (): Integer; inline;
 
+    function getProxyById (idx: TBodyProxyId): PBodyProxyRec; inline;
+
   public
     constructor Create (aMinPixX, aMinPixY, aPixWidth, aPixHeight: Integer{; aTileSize: Integer=GridDefaultTileSize});
     destructor Destroy (); override;
@@ -143,6 +186,8 @@ type
     // no callback: return object on the first hit or nil
     function forEachAtPoint (x, y: Integer; cb: TGridQueryCB; tagmask: Integer=-1; exittag: PInteger=nil): ITP;
 
+    function atCellInPoint (x, y: Integer): TAtPointEnumerator;
+
     //WARNING: don't modify grid while any query is in progress (no checks are made!)
     //         you can set enabled/disabled flag, tho (but iterator can still return objects disabled inside it)
     // cb with `(nil)` will be called before processing new tile
@@ -152,20 +197,22 @@ type
     function traceRay (const x0, y0, x1, y1: Integer; cb: TGridRayQueryCB; tagmask: Integer=-1): ITP; overload;
     function traceRay (out ex, ey: Integer; const ax0, ay0, ax1, ay1: Integer; cb: TGridRayQueryCB; tagmask: Integer=-1): ITP;
 
-    //function traceOrthoRayWhileIn (const x0, y0, x1, y1: Integer; tagmask: Integer=-1): ITP; overload;
-    //function traceOrthoRayWhileIn (out ex, ey: Integer; const ax0, ay0, ax1, ay1: Integer; tagmask: Integer=-1): ITP;
+    // return `false` if we're still inside at the end
+    // line should be either strict horizontal, or strict vertical, otherwise an exception will be thrown
+    function traceOrthoRayWhileIn (out ex, ey: Integer; ax0, ay0, ax1, ay1: Integer; tagmask: Integer=-1): Boolean;
 
     //WARNING: don't modify grid while any query is in progress (no checks are made!)
     //         you can set enabled/disabled flag, tho (but iterator can still return objects disabled inside it)
     // trace line along the grid, calling `cb` for all objects in passed cells, in no particular order
     //WARNING: don't change tags in callbacks here!
-    function forEachAlongLine (const x0, y0, x1, y1: Integer; cb: TGridAlongQueryCB; tagmask: Integer=-1; log: Boolean=false): ITP;
+    function forEachAlongLine (ax0, ay0, ax1, ay1: Integer; cb: TGridQueryCB; tagmask: Integer=-1; log: Boolean=false): ITP;
 
     // debug
     procedure forEachBodyCell (body: TBodyProxyId; cb: TCellQueryCB);
     function forEachInCell (x, y: Integer; cb: TGridQueryCB): ITP;
     procedure dumpStats ();
 
+  public
     //WARNING! no sanity checks!
     property proxyEnabled[pid: TBodyProxyId]: Boolean read getProxyEnabled write setProxyEnabled;
 
@@ -173,6 +220,8 @@ type
     property gridY0: Integer read mMinY;
     property gridWidth: Integer read getGridWidthPx; // in pixels
     property gridHeight: Integer read getGridHeightPx; // in pixels
+
+    property proxy[idx: TBodyProxyId]: PBodyProxyRec read getProxyById;
   end;
 
 
@@ -192,7 +241,7 @@ function maxInt (a, b: Integer): Integer; inline;
 implementation
 
 uses
-  SysUtils, e_log;
+  SysUtils, e_log, g_console, utils;
 
 
 // ////////////////////////////////////////////////////////////////////////// //
@@ -378,6 +427,71 @@ begin
 end;
 
 
+function TBodyGridBase.TBodyProxyRec.getTag (): Integer; inline;
+begin
+  result := mTag and TagFullMask;
+end;
+
+procedure TBodyGridBase.TBodyProxyRec.setTag (v: Integer); inline;
+begin
+  mTag := (mTag and TagDisabled) or (v and TagFullMask);
+end;
+
+function TBodyGridBase.TBodyProxyRec.getEnabled (): Boolean; inline;
+begin
+  result := ((mTag and TagDisabled) = 0);
+end;
+
+procedure TBodyGridBase.TBodyProxyRec.setEnabled (v: Boolean); inline;
+begin
+  if v then mTag := mTag and (not TagDisabled) else mTag := mTag or TagDisabled;
+end;
+
+function TBodyGridBase.TBodyProxyRec.getX1 (): Integer; inline;
+begin
+  result := mX+mWidth-1;
+end;
+
+function TBodyGridBase.TBodyProxyRec.getY1 (): Integer; inline;
+begin
+  result := mY+mHeight-1;
+end;
+
+
+// ////////////////////////////////////////////////////////////////////////// //
+constructor TBodyGridBase.TAtPointEnumerator.Create (acells: TCellArray; aidx: Integer; agetpx: TGetProxyFn);
+begin
+  mCells := acells;
+  curidx := aidx;
+  curbki := -1;
+  getpx := agetpx;
+end;
+
+
+function TBodyGridBase.TAtPointEnumerator.MoveNext (): Boolean; inline;
+begin
+  while (curidx <> -1) do
+  begin
+    while (curbki < GridCellBucketSize) do
+    begin
+      Inc(curbki);
+      if (mCells[curidx].bodies[curbki] = -1) then break;
+      result := true;
+      exit;
+    end;
+    curidx := mCells[curidx].next;
+    curbki := -1;
+  end;
+  result := false;
+end;
+
+
+function TBodyGridBase.TAtPointEnumerator.getCurrent (): PBodyProxyRec; inline;
+begin
+  result := getpx(mCells[curidx].bodies[curbki]);
+end;
+
+
 // ////////////////////////////////////////////////////////////////////////// //
 constructor TBodyGridBase.Create (aMinPixX, aMinPixY, aPixWidth, aPixHeight: Integer{; aTileSize: Integer=GridDefaultTileSize});
 var
@@ -591,6 +705,12 @@ begin
 end;
 
 
+function TBodyGridBase.getProxyById (idx: TBodyProxyId): PBodyProxyRec; inline;
+begin
+  if (idx >= 0) and (idx < High(mProxies)) then result := @mProxies[idx] else result := nil;
+end;
+
+
 // ////////////////////////////////////////////////////////////////////////// //
 function TBodyGridBase.allocCell (): Integer;
 var
@@ -1060,6 +1180,18 @@ begin
 end;
 
 
+// ////////////////////////////////////////////////////////////////////////// //
+function TBodyGridBase.atCellInPoint (x, y: Integer): TAtPointEnumerator;
+var
+  cidx: Integer = -1;
+begin
+  Dec(x, mMinX);
+  Dec(y, mMinY);
+  if (x >= 0) and (y >= 0) and (x < mWidth*mTileSize) and (y < mHeight*mTileSize) then cidx := mGrid[(y div mTileSize)*mWidth+(x div mTileSize)];
+  result := TAtPointEnumerator.Create(mCells, cidx, getProxyById);
+end;
+
+
 // ////////////////////////////////////////////////////////////////////////// //
 // no callback: return `true` on the first hit
 function TBodyGridBase.forEachAtPoint (x, y: Integer; cb: TGridQueryCB; tagmask: Integer=-1; exittag: PInteger=nil): ITP;
@@ -1188,6 +1320,9 @@ begin
   if (x+w <= 0) or (y+h <= 0) then exit;
   if (x >= gw*tsize) or (y >= mHeight*tsize) then exit;
 
+  if mInQuery then raise Exception.Create('recursive queries aren''t supported');
+  mInQuery := true;
+
   // increase query counter
   Inc(mLastQuery);
   if (mLastQuery = 0) then
@@ -1227,11 +1362,12 @@ begin
           if (x0+w <= px.mX) or (y0+h <= px.mY) then continue;
           if assigned(cb) then
           begin
-            if cb(px.mObj, ptag) then begin result := px.mObj; exit; end;
+            if cb(px.mObj, ptag) then begin result := px.mObj; mInQuery := false; exit; end;
           end
           else
           begin
             result := px.mObj;
+            mInQuery := false;
             exit;
           end;
         end;
@@ -1239,6 +1375,8 @@ begin
       end;
     end;
   end;
+
+  mInQuery := false;
 end;
 
 
@@ -1283,9 +1421,15 @@ var
   lq: LongWord;
   f, ptag, distSq: Integer;
   x0, y0, x1, y1: Integer;
+  //swapped: Boolean = false; // true: xd is yd, and vice versa
   // horizontal walker
+  {$IFDEF GRID_USE_ORTHO_ACCEL}
   wklen, wkstep: Integer;
+  //wksign: Integer;
   hopt: Boolean;
+  {$ENDIF}
+  // skipper
+  xdist, ydist: Integer;
 begin
   result := Default(ITP);
   lastObj := Default(ITP);
@@ -1377,6 +1521,7 @@ begin
 
   if (dsx < dsy) then
   begin
+    //swapped := true;
     xptr := @yd;
     yptr := @xd;
     swapInt(x0, y0);
@@ -1450,6 +1595,7 @@ begin
   // DON'T DO THIS! loop will take care of that
   if (xd = term) then
   begin
+    //FIXME!
     result := forEachAtPoint(ax0, ay0, nil, tagmask, @ptag);
     if (result <> nil) then
     begin
@@ -1497,6 +1643,9 @@ begin
 
   //if (dbgShowTraceLog) then e_WriteLog(Format('raycast start: (%d,%d)-(%d,%d); xptr^=%d; yptr^=%d', [ax0, ay0, ax1, ay1, xptr^, yptr^]), MSG_NOTIFY);
 
+  if mInQuery then raise Exception.Create('recursive queries aren''t supported');
+  mInQuery := true;
+
   // increase query counter
   Inc(mLastQuery);
   if (mLastQuery = 0) then
@@ -1508,15 +1657,15 @@ begin
   lq := mLastQuery;
 
   {$IFDEF GRID_USE_ORTHO_ACCEL}
-  // if this is strict horizontal trace, use optimized codepath
+  // if this is strict horizontal/vertical trace, use optimized codepath
   if (ax0 = ax1) or (ay0 = ay1) then
   begin
     // horizontal trace: walk the whole tiles, calculating mindist once for each proxy in cell
     //   stx < 0: going left, otherwise `stx` is > 0, and we're going right
     // vertical trace: walk the whole tiles, calculating mindist once for each proxy in cell
-    // stx < 0: going up, otherwise `stx` is > 0, and we're going down
+    //   stx < 0: going up, otherwise `stx` is > 0, and we're going down
     hopt := (ay0 = ay1); // horizontal?
-    if (stx < 0) then wklen := -(term-xd) else wklen := term-xd;
+    if (stx < 0) then begin {wksign := -1;} wklen := -(term-xd); end else begin {wksign := 1;} wklen := term-xd; end;
     {$IF DEFINED(D2F_DEBUG)}
     if dbgShowTraceLog then e_LogWritefln('optimized htrace; wklen=%d', [wklen]);
     {$ENDIF}
@@ -1524,16 +1673,6 @@ begin
     // one of those will never change
     x := xptr^+minx;
     y := yptr^+miny;
-    {$IF DEFINED(D2F_DEBUG)}
-    if hopt then
-    begin
-      if (y <> ay0) then raise Exception.Create('htrace fatal internal error');
-    end
-    else
-    begin
-      if (x <> ax0) then raise Exception.Create('vtrace fatal internal error');
-    end;
-    {$ENDIF}
     while (wklen > 0) do
     begin
       {$IF DEFINED(D2F_DEBUG)}
@@ -1556,24 +1695,25 @@ begin
             ptag := px.mTag;
             if ((ptag and TagDisabled) = 0) and ((ptag and tagmask) <> 0) and (px.mQueryMark <> lq) and
                // constant coord should be inside
-               ((hopt and (y >= px.mY) and (y < px.mY+px.mHeight)) or
-                ((not hopt) and (x >= px.mX) and (x < px.mX+px.mWidth))) then
+               ((hopt and (y >= px.y0) and (y <= px.y1)) or
+                ((not hopt) and (x >= px.x0) and (x <= px.x1))) then
             begin
               px.mQueryMark := lq; // mark as processed
               // inside the proxy?
-              if (hopt and (x > px.mX) and (x < px.mX+px.mWidth-1)) or
-                 ((not hopt) and (y > px.mY) and (y < px.mY+px.mHeight-1)) then
+              if (hopt and (x > px.x0) and (x < px.x1)) or
+                 ((not hopt) and (y > px.y0) and (y < px.y1)) then
               begin
+                // setup prev[xy]
                 if assigned(cb) then
                 begin
                   if cb(px.mObj, ptag, x, y, x, y) then
                   begin
-                    result := lastObj;
-                    ex := prevx;
-                    ey := prevy;
+                    result := px.mObj;
+                    ex := x;
+                    ey := y;
+                    mInQuery := false;
                     exit;
                   end;
-                  x := xptr^+minx;
                 end
                 else
                 begin
@@ -1586,63 +1726,64 @@ begin
                     ex := x;
                     ey := y;
                     result := px.mObj;
+                    mInQuery := false;
                     exit;
                   end;
                 end;
                 continue;
               end;
               // remember this hitpoint if it is nearer than an old one
+              // setup prev[xy]
               if hopt then
               begin
+                // horizontal trace
                 prevy := y;
+                y := yptr^+miny;
                 if (stx < 0) then
                 begin
                   // going left
-                  if (x < px.mX) then continue;
-                  prevx := px.mX+px.mWidth;
+                  if (x < px.x1) then continue; // not on the right edge
+                  x := px.x1;
+                  prevx := x+1;
                 end
                 else
                 begin
                   // going right
-                  if (x > px.mX{+px.mWidth}) then continue;
-                  prevx := px.mX-1;
+                  if (x > px.x0) then continue; // not on the left edge
+                  x := px.x0;
+                  prevx := x-1;
                 end;
               end
               else
               begin
+                // vertical trace
                 prevx := x;
+                x := xptr^+minx;
                 if (stx < 0) then
                 begin
                   // going up
-                  if (y < px.mY) then continue;
-                  prevy := px.mY+px.mHeight;
+                  if (y < px.y1) then continue; // not on the bottom edge
+                  y := px.y1;
+                  prevy := x+1;
                 end
                 else
                 begin
                   // going down
-                  if (y > px.mY{+px.mHeight}) then continue;
-                  prevy := px.mY-1;
+                  if (y > px.y0) then continue; // not on the top edge
+                  y := px.y0;
+                  prevy := y-1;
                 end;
               end;
               if assigned(cb) then
               begin
-                if (stx < 0) then
-                begin
-                  if hopt then x := prevx-1 else y := prevy-1;
-                end
-                else
-                begin
-                  if hopt then x := prevx+1 else y := prevy+1;
-                end;
                 if cb(px.mObj, ptag, x, y, prevx, prevy) then
                 begin
-                  result := lastObj;
+                  result := px.mObj;
                   ex := prevx;
                   ey := prevy;
+                  mInQuery := false;
                   exit;
                 end;
-                x := xptr^+minx;
-                y := yptr^+miny;
               end
               else
               begin
@@ -1664,7 +1805,8 @@ begin
           // next cell
           ccidx := cc.next;
         end;
-        if wasHit and not assigned(cb) then begin result := lastObj; exit; end;
+        if wasHit and not assigned(cb) then begin result := lastObj; mInQuery := false; exit; end;
+        if assigned(cb) and cb(nil, 0, x, y, x, y) then begin result := lastObj; mInQuery := false; exit; end;
       end;
       // skip to next tile
       if hopt then
@@ -1703,7 +1845,7 @@ begin
           {$ENDIF}
           if (wkstep >= wklen) then break;
           Inc(yptr^, wkstep);
-          Inc(ga, mHeight);
+          Inc(ga, mWidth);
         end
         else
         begin
@@ -1714,13 +1856,14 @@ begin
           {$ENDIF}
           if (wkstep >= wklen) then break;
           Dec(yptr^, wkstep);
-          Dec(ga, mHeight);
+          Dec(ga, mWidth);
         end;
       end;
       Dec(wklen, wkstep);
     end;
     // we can travel less than one cell
     if wasHit and not assigned(cb) then result := lastObj else begin ex := ax1; ey := ay1; end;
+    mInQuery := false;
     exit;
   end;
   {$ENDIF}
@@ -1729,6 +1872,7 @@ begin
   if assigned(dbgRayTraceTileHitCB) then dbgRayTraceTileHitCB((xptr^ div tsize*tsize)+minx, (yptr^ div tsize*tsize)+miny);
   {$ENDIF}
 
+  //e_LogWritefln('*********************', []);
   ccidx := -1;
   //  can omit checks
   while (xd <> term) do
@@ -1753,11 +1897,12 @@ begin
         // signal cell completion
         if assigned(cb) then
         begin
-          if cb(nil, 0, xptr^+minx, yptr^+miny, prevx, prevy) then begin result := lastObj; exit; end;
+          if cb(nil, 0, xptr^+minx, yptr^+miny, prevx, prevy) then begin result := lastObj; mInQuery := false; exit; end;
         end
         else if wasHit then
         begin
           result := lastObj;
+          mInQuery := false;
           exit;
         end;
       end;
@@ -1792,25 +1937,12 @@ begin
               begin
                 if cb(px.mObj, ptag, x, y, prevx, prevy) then
                 begin
-                  result := lastObj;
+                  result := px.mObj;
                   ex := prevx;
                   ey := prevy;
+                  mInQuery := false;
                   exit;
                 end;
-                (*
-                  {$IF DEFINED(D2F_DEBUG_RAYTRACE)}
-                  distSq := distanceSq(ax0, ay0, prevx, prevy);
-                  if assigned(dbgRayTraceTileHitCB) then e_WriteLog(Format('  hit(%d): a=(%d,%d), h=(%d,%d), p=(%d,%d); distsq=%d; lastsq=%d', [cc.bodies[f], ax0, ay0, x, y, prevx, prevy, distSq, lastDistSq]), MSG_NOTIFY);
-                  if (distSq < lastDistSq) then
-                  begin
-                    wasHit := true;
-                    lastDistSq := distSq;
-                    ex := prevx;
-                    ey := prevy;
-                    lastObj := px.mObj;
-                  end;
-                  {$ENDIF}
-                *)
               end
               else
               begin
@@ -1846,15 +1978,33 @@ begin
         ccidx := -1;
         if assigned(cb) then
         begin
-          if cb(nil, 0, x, y, prevx, prevy) then begin result := lastObj; exit; end;
+          if cb(nil, 0, x, y, prevx, prevy) then begin result := lastObj; mInQuery := false; exit; end;
         end
         else if wasHit then
         begin
           result := lastObj;
+          mInQuery := false;
           exit;
         end;
       end;
     end;
+    if (ccidx = -1) then
+    begin
+      // move to cell edge, as we have nothing to trace here anymore
+      if (stx < 0) then xdist := xd and (not (mTileSize-1)) else xdist := xd or (mTileSize-1);
+      if (sty < 0) then ydist := yd and (not (mTileSize-1)) else ydist := yd or (mTileSize-1);
+      //e_LogWritefln('0: swapped=%d; xd=%d; yd=%d; stx=%d; sty=%d; e=%d; dx2=%d; dy2=%d; term=%d; xdist=%d; ydist=%d', [swapped, xd, yd, stx, sty, e, dx2, dy2, term, xdist, ydist]);
+      while (xd <> xdist) and (yd <> ydist) do
+      begin
+        // step
+        xd += stx;
+        if (e >= 0) then begin yd += sty; e -= dx2; end else e += dy2;
+        //e_LogWritefln('  xd=%d; yd=%d', [xd, yd]);
+        if (xd = term) then break;
+      end;
+      //e_LogWritefln('1: swapped=%d; xd=%d; yd=%d; stx=%d; sty=%d; e=%d; dx2=%d; dy2=%d; term=%d; xdist=%d; ydist=%d', [swapped, xd, yd, stx, sty, e, dx2, dy2, term, xdist, ydist]);
+      if (xd = term) then break;
+    end;
     //putPixel(xptr^, yptr^);
     // move coords
     prevx := xptr^+minx;
@@ -1872,59 +2022,220 @@ begin
     ex := ax1; // why not?
     ey := ay1; // why not?
   end;
+
+  mInQuery := false;
 end;
 
 
 // ////////////////////////////////////////////////////////////////////////// //
 //FIXME! optimize this with real tile walking
-function TBodyGridBase.forEachAlongLine (const x0, y0, x1, y1: Integer; cb: TGridAlongQueryCB; tagmask: Integer=-1; log: Boolean=false): ITP;
+function TBodyGridBase.forEachAlongLine (ax0, ay0, ax1, ay1: Integer; cb: TGridQueryCB; tagmask: Integer=-1; log: Boolean=false): ITP;
 const
   tsize = mTileSize;
 var
-  i: Integer;
-  dx, dy, d: Integer;
-  xerr, yerr: Integer;
-  incx, incy: Integer;
-  stepx, stepy: Integer;
-  x, y: Integer;
-  maxx, maxy: Integer;
-  gw, gh: Integer;
-  ccidx: Integer;
-  curci: Integer;
+  wx0, wy0, wx1, wy1: Integer; // window coordinates
+  stx, sty: Integer; // "steps" for x and y axes
+  dsx, dsy: Integer; // "lengthes" for x and y axes
+  dx2, dy2: Integer; // "double lengthes" for x and y axes
+  xd, yd: Integer; // current coord
+  e: Integer; // "error" (as in bresenham algo)
+  rem: Integer;
+  term: Integer;
+  xptr, yptr: PInteger;
+  xfixed: Boolean;
+  temp: Integer;
+  ccidx, curci: Integer;
+  lastGA: Integer = -1;
+  ga: Integer;
+  gw, gh, minx, miny, maxx, maxy: Integer;
   cc: PGridCell;
   px: PBodyProxyRec;
   lq: LongWord;
-  minx, miny: Integer;
-  ptag: Integer;
-  lastWasInGrid: Boolean;
-  tbcross: Boolean;
-  f: Integer;
-  //tedist: Integer;
+  f, ptag: Integer;
+  x0, y0, x1, y1: Integer;
+  //swapped: Boolean = false; // true: xd is yd, and vice versa
+  // horizontal walker
+  {$IFDEF GRID_USE_ORTHO_ACCEL}
+  wklen, wkstep: Integer;
+  //wksign: Integer;
+  hopt: Boolean;
+  {$ENDIF}
+  // skipper
+  xdist, ydist: Integer;
 begin
   log := false;
   result := Default(ITP);
   tagmask := tagmask and TagFullMask;
   if (tagmask = 0) or not assigned(cb) then exit;
 
+  if (ax0 = ax1) and (ay0 = ay1) then
+  begin
+    result := forEachAtPoint(ax0, ay0, cb, tagmask, @ptag);
+    exit;
+  end;
+
+  gw := mWidth;
+  gh := mHeight;
   minx := mMinX;
   miny := mMinY;
+  maxx := gw*tsize-1;
+  maxy := gh*tsize-1;
+
+  x0 := ax0;
+  y0 := ay0;
+  x1 := ax1;
+  y1 := ay1;
+
+  // offset query coords to (0,0)-based
+  Dec(x0, minx);
+  Dec(y0, miny);
+  Dec(x1, minx);
+  Dec(y1, miny);
+
+  // clip rectange
+  wx0 := 0;
+  wy0 := 0;
+  wx1 := maxx;
+  wy1 := maxy;
 
-  dx := x1-x0;
-  dy := y1-y0;
+  // horizontal setup
+  if (x0 < x1) then
+  begin
+    // from left to right
+    if (x0 > wx1) or (x1 < wx0) then exit; // out of screen
+    stx := 1; // going right
+  end
+  else
+  begin
+    // from right to left
+    if (x1 > wx1) or (x0 < wx0) then exit; // out of screen
+    stx := -1; // going left
+    x0 := -x0;
+    x1 := -x1;
+    wx0 := -wx0;
+    wx1 := -wx1;
+    swapInt(wx0, wx1);
+  end;
 
-  if (dx > 0) then incx := 1 else if (dx < 0) then incx := -1 else incx := 0;
-  if (dy > 0) then incy := 1 else if (dy < 0) then incy := -1 else incy := 0;
+  // vertical setup
+  if (y0 < y1) then
+  begin
+    // from top to bottom
+    if (y0 > wy1) or (y1 < wy0) then exit; // out of screen
+    sty := 1; // going down
+  end
+  else
+  begin
+    // from bottom to top
+    if (y1 > wy1) or (y0 < wy0) then exit; // out of screen
+    sty := -1; // going up
+    y0 := -y0;
+    y1 := -y1;
+    wy0 := -wy0;
+    wy1 := -wy1;
+    swapInt(wy0, wy1);
+  end;
 
-  if (incx = 0) and (incy = 0) then exit; // just incase
+  dsx := x1-x0;
+  dsy := y1-y0;
 
-  dx := abs(dx);
-  dy := abs(dy);
+  if (dsx < dsy) then
+  begin
+    //swapped := true;
+    xptr := @yd;
+    yptr := @xd;
+    swapInt(x0, y0);
+    swapInt(x1, y1);
+    swapInt(dsx, dsy);
+    swapInt(wx0, wy0);
+    swapInt(wx1, wy1);
+    swapInt(stx, sty);
+  end
+  else
+  begin
+    xptr := @xd;
+    yptr := @yd;
+  end;
 
-  if (dx > dy) then d := dx else d := dy;
+  dx2 := 2*dsx;
+  dy2 := 2*dsy;
+  xd := x0;
+  yd := y0;
+  e := 2*dsy-dsx;
+  term := x1;
 
-  // `x` and `y` will be in grid coords
-  x := x0-minx;
-  y := y0-miny;
+  xfixed := false;
+  if (y0 < wy0) then
+  begin
+    // clip at top
+    temp := dx2*(wy0-y0)-dsx;
+    xd += temp div dy2;
+    rem := temp mod dy2;
+    if (xd > wx1) then exit; // x is moved out of clipping rect, nothing to do
+    if (xd+1 >= wx0) then
+    begin
+      yd := wy0;
+      e -= rem+dsx;
+      if (rem > 0) then begin Inc(xd); e += dy2; end;
+      xfixed := true;
+    end;
+  end;
+
+  if (not xfixed) and (x0 < wx0) then
+  begin
+    // clip at left
+    temp := dy2*(wx0-x0);
+    yd += temp div dx2;
+    rem := temp mod dx2;
+    if (yd > wy1) or (yd = wy1) and (rem >= dsx) then exit;
+    xd := wx0;
+    e += rem;
+    if (rem >= dsx) then begin Inc(yd); e -= dx2; end;
+  end;
+
+  if (y1 > wy1) then
+  begin
+    // clip at bottom
+    temp := dx2*(wy1-y0)+dsx;
+    term := x0+temp div dy2;
+    rem := temp mod dy2;
+    if (rem = 0) then Dec(term);
+  end;
+
+  if (term > wx1) then term := wx1; // clip at right
+
+  Inc(term); // draw last point
+  //if (term = xd) then exit; // this is the only point, get out of here
+
+  if (sty = -1) then yd := -yd;
+  if (stx = -1) then begin xd := -xd; term := -term; end;
+  dx2 -= dy2;
+
+  // first move, to skip starting point
+  // DON'T DO THIS! loop will take care of that
+  if (xd = term) then
+  begin
+    result := forEachAtPoint(ax0, ay0, cb, tagmask, @ptag);
+    exit;
+  end;
+
+  (*
+  // move coords
+  if (e >= 0) then begin yd += sty; e -= dx2; end else e += dy2;
+  xd += stx;
+  // done?
+  if (xd = term) then exit;
+  *)
+
+  {$IF DEFINED(D2F_DEBUG)}
+  if (xptr^ < 0) or (yptr^ < 0) or (xptr^ >= gw*tsize) and (yptr^ >= gh*tsize) then raise Exception.Create('raycaster internal error (0)');
+  {$ENDIF}
+  // DON'T DO THIS! loop will take care of that
+  //lastGA := (yptr^ div tsize)*gw+(xptr^ div tsize);
+  //ccidx := mGrid[lastGA];
+
+  if mInQuery then raise Exception.Create('recursive queries aren''t supported');
+  mInQuery := true;
 
   // increase query counter
   Inc(mLastQuery);
@@ -1932,137 +2243,151 @@ begin
   begin
     // just in case of overflow
     mLastQuery := 1;
-    for i := 0 to High(mProxies) do mProxies[i].mQueryMark := 0;
+    for f := 0 to High(mProxies) do mProxies[f].mQueryMark := 0;
   end;
   lq := mLastQuery;
 
-  // cache various things
-  //tsize := mTileSize;
-  gw := mWidth;
-  gh := mHeight;
-  maxx := gw*tsize-1;
-  maxy := gh*tsize-1;
-
-  // setup distance and flags
-  lastWasInGrid := (x >= 0) and (y >= 0) and (x <= maxx) and (y <= maxy);
-
-  // setup starting tile ('cause we'll adjust tile vars only on tile edge crossing)
-  if lastWasInGrid then ccidx := mGrid[(y div tsize)*gw+(x div tsize)] else ccidx := -1;
-
-  // it is slightly faster this way
-  xerr := -d;
-  yerr := -d;
-
-  if (log) then e_WriteLog(Format('tracing: (%d,%d)-(%d,%d)', [x, y, x1-minx, y1-miny]), MSG_NOTIFY);
-
-  // now trace
-  i := 0;
-  while (i < d) do
+  {$IFDEF GRID_USE_ORTHO_ACCEL}
+  // if this is strict horizontal/vertical trace, use optimized codepath
+  if (ax0 = ax1) or (ay0 = ay1) then
   begin
-    Inc(i);
-    // do one step
-    xerr += dx;
-    yerr += dy;
-    // invariant: one of those always changed
-    {$IF DEFINED(D2F_DEBUG)}
-    if (xerr < 0) and (yerr < 0) then raise Exception.Create('internal bug in grid raycaster (0)');
-    {$ENDIF}
-    if (xerr >= 0) then begin xerr -= d; x += incx; stepx := incx; end else stepx := 0;
-    if (yerr >= 0) then begin yerr -= d; y += incy; stepy := incy; end else stepy := 0;
-    // invariant: we always doing a step
+    // horizontal trace: walk the whole tiles, calculating mindist once for each proxy in cell
+    //   stx < 0: going left, otherwise `stx` is > 0, and we're going right
+    // vertical trace: walk the whole tiles, calculating mindist once for each proxy in cell
+    //   stx < 0: going up, otherwise `stx` is > 0, and we're going down
+    hopt := (ay0 = ay1); // horizontal?
+    if (stx < 0) then begin {wksign := -1;} wklen := -(term-xd); end else begin {wksign := 1;} wklen := term-xd; end;
     {$IF DEFINED(D2F_DEBUG)}
-    if ((stepx or stepy) = 0) then raise Exception.Create('internal bug in grid raycaster (1)');
+    if dbgShowTraceLog then e_LogWritefln('optimized htrace; wklen=%d', [wklen]);
     {$ENDIF}
+    ga := (yptr^ div tsize)*gw+(xptr^ div tsize);
+    while (wklen > 0) do
     begin
-      // check for crossing tile/grid boundary
-      if (x >= 0) and (y >= 0) and (x <= maxx) and (y <= maxy) then
+      {$IF DEFINED(D2F_DEBUG)}
+      if dbgShowTraceLog then e_LogWritefln('  htrace; ga=%d; x=%d, y=%d; ay0=%d', [ga, xptr^+minx, yptr^+miny, ay0]);
+      {$ENDIF}
+      // new tile?
+      if (ga <> lastGA) then
       begin
-        // we're still in grid
-        lastWasInGrid := true;
-        // check for tile edge crossing
-             if (stepx < 0) and ((x mod tsize) = tsize-1) then tbcross := true
-        else if (stepx > 0) and ((x mod tsize) = 0) then tbcross := true
-        else if (stepy < 0) and ((y mod tsize) = tsize-1) then tbcross := true
-        else if (stepy > 0) and ((y mod tsize) = 0) then tbcross := true
-        else tbcross := false;
-        // crossed tile edge?
-        if tbcross then
-        begin
-          // setup new cell index
-          ccidx := mGrid[(y div tsize)*gw+(x div tsize)];
-          if (log) then e_WriteLog(Format(' stepped to new tile (%d,%d) -- (%d,%d)', [(x div tsize), (y div tsize), x, y]), MSG_NOTIFY);
-        end
-        else
-        if (ccidx = -1) then
+        lastGA := ga;
+        ccidx := mGrid[lastGA];
+        // convert coords to map (to avoid ajdusting coords inside the loop)
+        while (ccidx <> -1) do
         begin
-          // we have nothing interesting here anymore, jump directly to tile edge
-          (*
-          if (incx = 0) then
-          begin
-            // vertical line
-            if (incy < 0) then tedist := y-(y and (not tsize)) else tedist := (y or (tsize-1))-y;
-            if (tedist > 1) then
-            begin
-              if (log) then e_WriteLog(Format('  doing vertical jump from tile (%d,%d) - (%d,%d) by %d steps', [(x div tsize), (y div tsize), x, y, tedist]), MSG_NOTIFY);
-              y += incy*tedist;
-              Inc(i, tedist);
-              if (log) then e_WriteLog(Format('   jumped to tile (%d,%d) - (%d,%d) by %d steps', [(x div tsize), (y div tsize), x, y, tedist]), MSG_NOTIFY);
-            end;
-          end
-          else if (incy = 0) then
+          cc := @mCells[ccidx];
+          for f := 0 to GridCellBucketSize-1 do
           begin
-            // horizontal line
-            if (incx < 0) then tedist := x-(x and (not tsize)) else tedist := (x or (tsize-1))-x;
-            if (tedist > 1) then
+            if (cc.bodies[f] = -1) then break;
+            px := @mProxies[cc.bodies[f]];
+            ptag := px.mTag;
+            if ((ptag and TagDisabled) = 0) and ((ptag and tagmask) <> 0) and (px.mQueryMark <> lq) then
             begin
-              if (log) then e_WriteLog(Format('  doing horizontal jump from tile (%d,%d) - (%d,%d) by %d steps', [(x div tsize), (y div tsize), x, y, tedist]), MSG_NOTIFY);
-              x += incx*tedist;
-              Inc(i, tedist);
-              if (log) then e_WriteLog(Format('   jumped to tile (%d,%d) - (%d,%d) by %d steps', [(x div tsize), (y div tsize), x, y, tedist]), MSG_NOTIFY);
+              px.mQueryMark := lq; // mark as processed
+              if assigned(cb) then
+              begin
+                if cb(px.mObj, ptag) then begin result := px.mObj; mInQuery := false; exit; end;
+              end
+              else
+              begin
+                result := px.mObj;
+                mInQuery := false;
+                exit;
+              end;
             end;
           end;
-          *)
-          (*
-           else if (
-          // get minimal distance to tile edges
-          if (incx < 0) then tedist := x-(x and (not tsize)) else if (incx > 0) then tedist := (x or (tsize+1))-x else tedist := 0;
+          // next cell
+          ccidx := cc.next;
+        end;
+      end;
+      // skip to next tile
+      if hopt then
+      begin
+        if (stx > 0) then
+        begin
+          // to the right
+          wkstep := ((xptr^ or (mTileSize-1))+1)-xptr^;
           {$IF DEFINED(D2F_DEBUG)}
-          if (tedist < 0) then raise Exception.Create('internal bug in grid raycaster (2.x)');
+          if dbgShowTraceLog then e_LogWritefln('  right step: wklen=%d; wkstep=%d', [wklen, wkstep]);
           {$ENDIF}
-          if (incy < 0) then f := y-(y and (not tsize)) else if (incy > 0) then f := (y or (tsize+1))-y else f := 0;
+          if (wkstep >= wklen) then break;
+          Inc(xptr^, wkstep);
+          Inc(ga);
+        end
+        else
+        begin
+          // to the left
+          wkstep := xptr^-((xptr^ and (not (mTileSize-1)))-1);
           {$IF DEFINED(D2F_DEBUG)}
-          if (f < 0) then raise Exception.Create('internal bug in grid raycaster (2.y)');
+          if dbgShowTraceLog then e_LogWritefln('  left step: wklen=%d; wkstep=%d', [wklen, wkstep]);
           {$ENDIF}
-          if (tedist = 0) then tedist := f else if (f <> 0) then tedist := minInt(tedist, f);
-          // do jump
-          if (tedist > 1) then
-          begin
-            if (log) then e_WriteLog(Format('  doing jump from tile (%d,%d) - (%d,%d) by %d steps', [(x div tsize), (y div tsize), x, y, tedist]), MSG_NOTIFY);
-            xerr += dx*tedist;
-            yerr += dy*tedist;
-            if (xerr >= 0) then begin x += incx*((xerr div d)+1); xerr := (xerr mod d)-d; end;
-            if (yerr >= 0) then begin y += incy*((yerr div d)+1); yerr := (yerr mod d)-d; end;
-            Inc(i, tedist);
-            if (log) then e_WriteLog(Format('   jumped to tile (%d,%d) - (%d,%d) by %d steps', [(x div tsize), (y div tsize), x, y, tedist]), MSG_NOTIFY);
-          end;
-          *)
+          if (wkstep >= wklen) then break;
+          Dec(xptr^, wkstep);
+          Dec(ga);
         end;
       end
       else
       begin
-        // out of grid
-        if lastWasInGrid then exit; // oops, stepped out of the grid -- there is no way to return
+        if (stx > 0) then
+        begin
+          // to the down
+          wkstep := ((yptr^ or (mTileSize-1))+1)-yptr^;
+          {$IF DEFINED(D2F_DEBUG)}
+          if dbgShowTraceLog then e_LogWritefln('  down step: wklen=%d; wkstep=%d', [wklen, wkstep]);
+          {$ENDIF}
+          if (wkstep >= wklen) then break;
+          Inc(yptr^, wkstep);
+          Inc(ga, mWidth);
+        end
+        else
+        begin
+          // to the up
+          wkstep := yptr^-((yptr^ and (not (mTileSize-1)))-1);
+          {$IF DEFINED(D2F_DEBUG)}
+          if dbgShowTraceLog then e_LogWritefln('  up step: wklen=%d; wkstep=%d', [wklen, wkstep]);
+          {$ENDIF}
+          if (wkstep >= wklen) then break;
+          Dec(yptr^, wkstep);
+          Dec(ga, mWidth);
+        end;
       end;
+      Dec(wklen, wkstep);
     end;
+    mInQuery := false;
+    exit;
+  end;
+  {$ENDIF}
 
-    // has something to process in the current cell?
+  {$IF DEFINED(D2F_DEBUG_RAYTRACE)}
+  if assigned(dbgRayTraceTileHitCB) then dbgRayTraceTileHitCB((xptr^ div tsize*tsize)+minx, (yptr^ div tsize*tsize)+miny);
+  {$ENDIF}
+
+  ccidx := -1;
+  //  can omit checks
+  while (xd <> term) do
+  begin
+    // check cell(s)
+    {$IF DEFINED(D2F_DEBUG)}
+    if (xptr^ < 0) or (yptr^ < 0) or (xptr^ >= gw*tsize) and (yptr^ >= gh*tsize) then raise Exception.Create('raycaster internal error (0)');
+    {$ENDIF}
+    // new tile?
+    ga := (yptr^ div tsize)*gw+(xptr^ div tsize);
+    {$IF DEFINED(D2F_DEBUG_RAYTRACE)}
+    if assigned(dbgRayTraceTileHitCB) then e_WriteLog(Format(' xd=%d; term=%d; gx=%d; gy=%d; ga=%d; lastga=%d', [xd, term, xptr^, yptr^, ga, lastGA]), MSG_NOTIFY);
+    {$ENDIF}
+    if (ga <> lastGA) then
+    begin
+      // yes
+      {$IF DEFINED(D2F_DEBUG)}
+      if assigned(dbgRayTraceTileHitCB) then dbgRayTraceTileHitCB((xptr^ div tsize*tsize)+minx, (yptr^ div tsize*tsize)+miny);
+      {$ENDIF}
+      lastGA := ga;
+      ccidx := mGrid[lastGA];
+    end;
+    // has something to process in this tile?
     if (ccidx <> -1) then
     begin
       // process cell
       curci := ccidx;
-      // convert coords to map (to avoid ajdusting coords inside the loop)
-      //Inc(x, minx);
-      //Inc(y, miny);
       // process cell list
       while (curci <> -1) do
       begin
@@ -2075,17 +2400,175 @@ begin
           if ((ptag and TagDisabled) = 0) and ((ptag and tagmask) <> 0) and (px.mQueryMark <> lq) then
           begin
             px.mQueryMark := lq; // mark as processed
-            if cb(px.mObj, ptag) then begin result := px.mObj; exit; end;
+            if assigned(cb) then
+            begin
+              if cb(px.mObj, ptag) then begin result := px.mObj; mInQuery := false; exit; end;
+            end
+            else
+            begin
+              result := px.mObj;
+              mInQuery := false;
+              exit;
+            end;
           end;
         end;
         // next cell
         curci := cc.next;
       end;
-      ccidx := -1; // don't process this anymore
-      // convert coords to grid
-      //Dec(x, minx);
-      //Dec(y, miny);
+      // nothing more interesting in this cell
+      ccidx := -1;
     end;
+    // move to cell edge, as we have nothing to trace here anymore
+    if (stx < 0) then xdist := xd and (not (mTileSize-1)) else xdist := xd or (mTileSize-1);
+    if (sty < 0) then ydist := yd and (not (mTileSize-1)) else ydist := yd or (mTileSize-1);
+    //e_LogWritefln('0: swapped=%d; xd=%d; yd=%d; stx=%d; sty=%d; e=%d; dx2=%d; dy2=%d; term=%d; xdist=%d; ydist=%d', [swapped, xd, yd, stx, sty, e, dx2, dy2, term, xdist, ydist]);
+    while (xd <> xdist) and (yd <> ydist) do
+    begin
+      // step
+      xd += stx;
+      if (e >= 0) then begin yd += sty; e -= dx2; end else e += dy2;
+      //e_LogWritefln('  xd=%d; yd=%d', [xd, yd]);
+      if (xd = term) then break;
+    end;
+    //e_LogWritefln('1: swapped=%d; xd=%d; yd=%d; stx=%d; sty=%d; e=%d; dx2=%d; dy2=%d; term=%d; xdist=%d; ydist=%d', [swapped, xd, yd, stx, sty, e, dx2, dy2, term, xdist, ydist]);
+    if (xd = term) then break;
+    //putPixel(xptr^, yptr^);
+    // move coords
+    if (e >= 0) then begin yd += sty; e -= dx2; end else e += dy2;
+    xd += stx;
+  end;
+
+  mInQuery := false;
+end;
+
+
+{.$DEFINE D2F_DEBUG_OTR}
+function TBodyGridBase.traceOrthoRayWhileIn (out ex, ey: Integer; ax0, ay0, ax1, ay1: Integer; tagmask: Integer=-1): Boolean;
+var
+  ccidx: Integer;
+  cc: PGridCell;
+  px: PBodyProxyRec;
+  ptag: Integer;
+  minx, miny: Integer;
+  f, c0, c1: Integer;
+  x0, y0, x1, y1: Integer;
+  celly0, celly1: Integer;
+  dy: Integer;
+  filled: array[0..mTileSize-1] of Byte;
+  {$IF DEFINED(D2F_DEBUG_OTR)}
+  s: AnsiString = '';
+  {$ENDIF}
+begin
+  result := false;
+  ex := ax1;
+  ey := ay1;
+  if not ((ax0 = ax1) or (ay0 = ay1)) then raise Exception.Create('orthoray is not orthogonal');
+
+  tagmask := tagmask and TagFullMask;
+  if (tagmask = 0) then exit;
+
+  if (forEachAtPoint(ax0, ay0, nil, tagmask) = nil) then exit;
+
+  minx := mMinX;
+  miny := mMinY;
+
+  // offset query coords to (0,0)-based
+  x0 := ax0-minx;
+  y0 := ay0-miny;
+  x1 := ax1-minx;
+  y1 := ay1-miny;
+
+  if (x0 = x1) then
+  begin
+    if (x0 < 0) or (x0 >= mWidth*mTileSize) then exit; // oops
+    // vertical
+    if (y0 < y1) then
+    begin
+      // down
+      if (y1 < 0) or (y0 >= mHeight*mTileSize) then exit;
+      //if (ay0 < 0) then ay0 := 0;
+      if (y0 < 0) then exit;
+      if (y1 >= mHeight*mTileSize) then y1 := mHeight*mTileSize-1;
+      dy := 1;
+    end
+    else
+    begin
+      // up
+      if (y0 < 0) or (y1 >= mHeight*mTileSize) then exit;
+      //if (ay1 < 0) then ay1 := 0;
+      if (y1 < 0) then exit;
+      if (y0 >= mHeight*mTileSize) then y0 := mHeight*mTileSize-1;
+      dy := -1;
+    end;
+    // check tile
+    while true do
+    begin
+      ccidx := mGrid[(y0 div mTileSize)*mWidth+(x0 div mTileSize)];
+      FillChar(filled, sizeof(filled), 0);
+      celly0 := y0 and (not (mTileSize-1));
+      celly1 := celly0+mTileSize-1;
+      while (ccidx <> -1) do
+      begin
+        cc := @mCells[ccidx];
+        for f := 0 to GridCellBucketSize-1 do
+        begin
+          if (cc.bodies[f] = -1) then break;
+          px := @mProxies[cc.bodies[f]];
+          ptag := px.mTag;
+          if ((ptag and TagDisabled) = 0) and ((ptag and tagmask) <> 0) and
+             (ax0 >= px.x0) and (ax0 <= px.x1) then
+          begin
+            // bound c0 and c1 to cell
+            c0 := nclamp(px.y0-miny, celly0, celly1);
+            c1 := nclamp(px.y1-miny, celly0, celly1);
+            // fill the thing
+            {$IF DEFINED(D2F_DEBUG_OTR)}
+            e_LogWritefln('**px.y0=%s; px.y1=%s; c0=%s; c1=%s; celly0=%s; celly1=%s; [%s..%s]', [px.y0-miny, px.y1-miny, c0, c1, celly0, celly1, c0-celly0, (c0-celly0)+(c1-c0)]);
+            {$ENDIF}
+            //assert(c0 <= c1);
+            FillChar(filled[c0-celly0], c1-c0+1, 1);
+          end;
+        end;
+        // next cell
+        ccidx := cc.next;
+      end;
+      {$IF DEFINED(D2F_DEBUG_OTR)}
+      s := formatstrf('  x=%s; ay0=%s; ay1=%s; y0=%s; celly0=%s; celly1=%s; dy=%s; [', [ax0, ay0, ay1, y0, celly0, celly1, dy]);
+      for f := 0 to High(filled) do if (filled[f] <> 0) then s += '1' else s += '0';
+      s += ']';
+      e_LogWriteln(s);
+      {$ENDIF}
+      // now go till we hit cell boundary or empty space
+      if (dy < 0) then
+      begin
+        // up
+        while (y0 >= celly0) and (filled[y0-celly0] <> 0) do
+        begin
+          {$IF DEFINED(D2F_DEBUG_OTR)}
+          e_LogWritefln('   filled: cdy=%s; y0=%s; celly0=%s; ay0=%s; ay1=%s', [y0-celly0, y0, celly0, ay0, ay1]);
+          {$ENDIF}
+          Dec(y0);
+          Dec(ay0);
+        end;
+        {$IF DEFINED(D2F_DEBUG_OTR)}
+        e_LogWritefln('   span done: cdy=%s; y0=%s; celly0=%s; ay0=%s; ay1=%s', [y0-celly0, y0, celly0, ay0, ay1]);
+        {$ENDIF}
+        if (ay0 <= ay1) then begin ey := ay1; result := false; exit; end;
+        if (y0 >= celly0) then begin ey := ay0+1; {assert(forEachAtPoint(ex, ey, nil, tagmask) <> nil);} result := true; exit; end;
+      end
+      else
+      begin
+        // down
+        while (y0 <= celly1) and (filled[y1-celly0] <> 0) do begin Inc(y0); Inc(ay0); end;
+        if (ay0 >= ay1) then begin ey := ay1; result := false; exit; end;
+        if (y0 <= celly1) then begin ey := ay0-1; result := true; exit; end;
+      end;
+    end;
+  end
+  else
+  begin
+    // horizontal
+    assert(false);
   end;
 end;