339 lines
6.9 KiB
C
339 lines
6.9 KiB
C
// Emacs style mode select -*- C++ -*-
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//-----------------------------------------------------------------------------
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//
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// $Id:$
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//
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// Copyright (C) 1993-1996 by id Software, Inc.
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//
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// This source is available for distribution and/or modification
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// only under the terms of the DOOM Source Code License as
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// published by id Software. All rights reserved.
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//
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// The source is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
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// for more details.
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//
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// $Log:$
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//
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// DESCRIPTION:
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// LineOfSight/Visibility checks, uses REJECT Lookup Table.
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//
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//-----------------------------------------------------------------------------
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//static const char
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#include "doomdef.h"
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#include "i_system.h"
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#include "p_local.h"
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// State.
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#include "r_state.h"
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//
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// P_CheckSight
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//
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fixed_t sightzstart; // eye z of looker
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fixed_t topslope;
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fixed_t bottomslope; // slopes to top and bottom of target
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divline_t strace; // from t1 to t2
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fixed_t t2x;
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fixed_t t2y;
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int sightcounts[2];
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//
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// P_DivlineSide
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// Returns side 0 (front), 1 (back), or 2 (on).
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//
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int P_DivlineSide( fixed_t x, fixed_t y, divline_t* node )
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{
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fixed_t dx;
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fixed_t dy;
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fixed_t left;
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fixed_t right;
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if (!node->dx)
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{
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if (x==node->x)
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return 2;
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if (x <= node->x)
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return node->dy > 0;
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return node->dy < 0;
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}
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if (!node->dy)
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{
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if (x==node->y)
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return 2;
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if (y <= node->y)
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return node->dx < 0;
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return node->dx > 0;
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}
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dx = (x - node->x);
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dy = (y - node->y);
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left = (node->dy>>FRACBITS) * (dx>>FRACBITS);
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right = (dy>>FRACBITS) * (node->dx>>FRACBITS);
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if (right < left)
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return 0; // front side
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if (left == right)
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return 2;
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return 1; // back side
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}
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//
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// P_InterceptVector2
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// Returns the fractional intercept point
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// along the first divline.
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// This is only called by the addthings and addlines traversers.
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//
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fixed_t P_InterceptVector2( divline_t* v2, divline_t* v1 )
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{
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fixed_t frac;
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fixed_t num;
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fixed_t den;
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den = FixedMul (v1->dy>>8,v2->dx) - FixedMul(v1->dx>>8,v2->dy);
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if (den == 0)
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return 0;
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// I_Error ("P_InterceptVector: parallel");
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num = FixedMul ( (v1->x - v2->x)>>8 ,v1->dy) +
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FixedMul ( (v2->y - v1->y)>>8 , v1->dx);
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frac = FixedDiv (num , den);
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return frac;
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}
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//
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// P_CrossSubsector
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// Returns true
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// if strace crosses the given subsector successfully.
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//
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boolean P_CrossSubsector (int num)
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{
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seg_t* seg;
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line_t* line;
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int s1;
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int s2;
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int count;
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subsector_t* sub;
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sector_t* front;
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sector_t* back;
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fixed_t opentop;
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fixed_t openbottom;
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divline_t divl;
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vertex_t* v1;
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vertex_t* v2;
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fixed_t frac;
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fixed_t slope;
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#ifdef RANGECHECK
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if (num>=numsubsectors)
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I_Error ("P_CrossSubsector: ss %i with numss = %i",
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num,
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numsubsectors);
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#endif
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sub = &subsectors[num];
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// check lines
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count = sub->numlines;
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seg = &segs[sub->firstline];
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for ( ; count ; seg++, count--)
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{
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line = seg->linedef;
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// allready checked other side?
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if (line->validcount == validcount)
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continue;
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line->validcount = validcount;
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v1 = line->v1;
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v2 = line->v2;
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s1 = P_DivlineSide (v1->x,v1->y, &strace);
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s2 = P_DivlineSide (v2->x, v2->y, &strace);
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// line isn't crossed?
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if (s1 == s2)
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continue;
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divl.x = v1->x;
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divl.y = v1->y;
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divl.dx = v2->x - v1->x;
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divl.dy = v2->y - v1->y;
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s1 = P_DivlineSide (strace.x, strace.y, &divl);
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s2 = P_DivlineSide (t2x, t2y, &divl);
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// line isn't crossed?
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if (s1 == s2)
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continue;
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// stop because it is not two sided anyway
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// might do this after updating validcount?
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if ( !(line->flags & ML_TWOSIDED) )
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return false;
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// crosses a two sided line
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front = seg->frontsector;
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back = seg->backsector;
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// no wall to block sight with?
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if (front->floorheight == back->floorheight
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&& front->ceilingheight == back->ceilingheight)
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continue;
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// possible occluder
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// because of ceiling height differences
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if (front->ceilingheight < back->ceilingheight)
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opentop = front->ceilingheight;
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else
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opentop = back->ceilingheight;
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// because of ceiling height differences
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if (front->floorheight > back->floorheight)
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openbottom = front->floorheight;
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else
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openbottom = back->floorheight;
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// quick test for totally closed doors
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if (openbottom >= opentop)
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return false; // stop
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frac = P_InterceptVector2 (&strace, &divl);
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if (front->floorheight != back->floorheight)
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{
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slope = FixedDiv (openbottom - sightzstart , frac);
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if (slope > bottomslope)
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bottomslope = slope;
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}
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if (front->ceilingheight != back->ceilingheight)
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{
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slope = FixedDiv (opentop - sightzstart , frac);
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if (slope < topslope)
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topslope = slope;
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}
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if (topslope <= bottomslope)
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return false; // stop
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}
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// passed the subsector ok
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return true;
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}
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//
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// P_CrossBSPNode
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// Returns true
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// if strace crosses the given node successfully.
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//
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boolean P_CrossBSPNode (int bspnum)
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{
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node_t* bsp;
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int side;
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if (bspnum & NF_SUBSECTOR)
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{
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if (bspnum == -1)
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return P_CrossSubsector (0);
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else
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return P_CrossSubsector (bspnum&(~NF_SUBSECTOR));
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}
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bsp = &nodes[bspnum];
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// decide which side the start point is on
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side = P_DivlineSide (strace.x, strace.y, (divline_t *)bsp);
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if (side == 2)
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side = 0; // an "on" should cross both sides
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// cross the starting side
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if (!P_CrossBSPNode (bsp->children[side]) )
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return false;
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// the partition plane is crossed here
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if (side == P_DivlineSide (t2x, t2y,(divline_t *)bsp))
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{
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// the line doesn't touch the other side
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return true;
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}
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// cross the ending side
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return P_CrossBSPNode (bsp->children[side^1]);
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}
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//
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// P_CheckSight
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// Returns true
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// if a straight line between t1 and t2 is unobstructed.
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// Uses REJECT.
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//
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boolean P_CheckSight ( mobj_t* t1, mobj_t* t2 )
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{
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int s1;
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int s2;
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int pnum;
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int bytenum;
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int bitnum;
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// First check for trivial rejection.
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// Determine subsector entries in REJECT table.
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s1 = (t1->subsector->sector - sectors);
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s2 = (t2->subsector->sector - sectors);
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pnum = s1*numsectors + s2;
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bytenum = pnum>>3;
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bitnum = 1 << (pnum&7);
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// Check in REJECT table.
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if (rejectmatrix[bytenum]&bitnum)
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{
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sightcounts[0]++;
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// can't possibly be connected
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return false;
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}
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// An unobstructed LOS is possible.
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// Now look from eyes of t1 to any part of t2.
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sightcounts[1]++;
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validcount++;
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sightzstart = t1->z + t1->height - (t1->height>>2);
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topslope = (t2->z+t2->height) - sightzstart;
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bottomslope = (t2->z) - sightzstart;
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strace.x = t1->x;
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strace.y = t1->y;
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t2x = t2->x;
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t2y = t2->y;
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strace.dx = t2->x - t1->x;
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strace.dy = t2->y - t1->y;
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// the head node is the last node output
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return P_CrossBSPNode (numnodes-1);
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}
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