ref: 2053768a9251cbd4c731681a3e1e04c800ad21f4
dir: /src/heretic/p_sight.c/
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 1993-2008 Raven Software
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// P_sight.c
#include <stdlib.h>
#include "doomdef.h"
#include "p_local.h"
/*
==============================================================================
P_CheckSight
This uses specialized forms of the maputils routines for optimized performance
==============================================================================
*/
fixed_t sightzstart; // eye z of looker
fixed_t topslope, bottomslope; // slopes to top and bottom of target
int sightcounts[3];
/*
==============
=
= PTR_SightTraverse
=
==============
*/
boolean PTR_SightTraverse(intercept_t * in)
{
line_t *li;
fixed_t slope;
li = in->d.line;
//
// crosses a two sided line
//
P_LineOpening(li);
if (openbottom >= opentop) // quick test for totally closed doors
return false; // stop
if (li->frontsector->floorheight != li->backsector->floorheight)
{
slope = FixedDiv(openbottom - sightzstart, in->frac);
if (slope > bottomslope)
bottomslope = slope;
}
if (li->frontsector->ceilingheight != li->backsector->ceilingheight)
{
slope = FixedDiv(opentop - sightzstart, in->frac);
if (slope < topslope)
topslope = slope;
}
if (topslope <= bottomslope)
return false; // stop
return true; // keep going
}
/*
==================
=
= P_SightBlockLinesIterator
=
===================
*/
boolean P_SightBlockLinesIterator(int x, int y)
{
int offset;
short *list;
line_t *ld;
int s1, s2;
divline_t dl;
offset = y * bmapwidth + x;
offset = *(blockmap + offset);
for (list = blockmaplump + offset; *list != -1; list++)
{
ld = &lines[*list];
if (ld->validcount == validcount)
continue; // line has already been checked
ld->validcount = validcount;
s1 = P_PointOnDivlineSide(ld->v1->x, ld->v1->y, &trace);
s2 = P_PointOnDivlineSide(ld->v2->x, ld->v2->y, &trace);
if (s1 == s2)
continue; // line isn't crossed
P_MakeDivline(ld, &dl);
s1 = P_PointOnDivlineSide(trace.x, trace.y, &dl);
s2 = P_PointOnDivlineSide(trace.x + trace.dx, trace.y + trace.dy,
&dl);
if (s1 == s2)
continue; // line isn't crossed
// try to early out the check
if (!ld->backsector)
return false; // stop checking
// store the line for later intersection testing
intercept_p->d.line = ld;
intercept_p++;
}
return true; // everything was checked
}
/*
====================
=
= P_SightTraverseIntercepts
=
= Returns true if the traverser function returns true for all lines
====================
*/
boolean P_SightTraverseIntercepts(void)
{
int count;
fixed_t dist;
intercept_t *scan, *in;
divline_t dl;
count = intercept_p - intercepts;
//
// calculate intercept distance
//
for (scan = intercepts; scan < intercept_p; scan++)
{
P_MakeDivline(scan->d.line, &dl);
scan->frac = P_InterceptVector(&trace, &dl);
}
//
// go through in order
//
in = 0; // shut up compiler warning
while (count--)
{
dist = INT_MAX;
for (scan = intercepts; scan < intercept_p; scan++)
if (scan->frac < dist)
{
dist = scan->frac;
in = scan;
}
if (!PTR_SightTraverse(in))
return false; // don't bother going farther
in->frac = INT_MAX;
}
return true; // everything was traversed
}
/*
==================
=
= P_SightPathTraverse
=
= Traces a line from x1,y1 to x2,y2, calling the traverser function for each
= Returns true if the traverser function returns true for all lines
==================
*/
boolean P_SightPathTraverse(fixed_t x1, fixed_t y1, fixed_t x2, fixed_t y2)
{
fixed_t xt1, yt1, xt2, yt2;
fixed_t xstep, ystep;
fixed_t partial;
fixed_t xintercept, yintercept;
int mapx, mapy, mapxstep, mapystep;
int count;
validcount++;
intercept_p = intercepts;
if (((x1 - bmaporgx) & (MAPBLOCKSIZE - 1)) == 0)
x1 += FRACUNIT; // don't side exactly on a line
if (((y1 - bmaporgy) & (MAPBLOCKSIZE - 1)) == 0)
y1 += FRACUNIT; // don't side exactly on a line
trace.x = x1;
trace.y = y1;
trace.dx = x2 - x1;
trace.dy = y2 - y1;
x1 -= bmaporgx;
y1 -= bmaporgy;
xt1 = x1 >> MAPBLOCKSHIFT;
yt1 = y1 >> MAPBLOCKSHIFT;
x2 -= bmaporgx;
y2 -= bmaporgy;
xt2 = x2 >> MAPBLOCKSHIFT;
yt2 = y2 >> MAPBLOCKSHIFT;
// points should never be out of bounds, but check once instead of
// each block
if (xt1 < 0 || yt1 < 0 || xt1 >= bmapwidth || yt1 >= bmapheight
|| xt2 < 0 || yt2 < 0 || xt2 >= bmapwidth || yt2 >= bmapheight)
return false;
if (xt2 > xt1)
{
mapxstep = 1;
partial = FRACUNIT - ((x1 >> MAPBTOFRAC) & (FRACUNIT - 1));
ystep = FixedDiv(y2 - y1, abs(x2 - x1));
}
else if (xt2 < xt1)
{
mapxstep = -1;
partial = (x1 >> MAPBTOFRAC) & (FRACUNIT - 1);
ystep = FixedDiv(y2 - y1, abs(x2 - x1));
}
else
{
mapxstep = 0;
partial = FRACUNIT;
ystep = 256 * FRACUNIT;
}
yintercept = (y1 >> MAPBTOFRAC) + FixedMul(partial, ystep);
if (yt2 > yt1)
{
mapystep = 1;
partial = FRACUNIT - ((y1 >> MAPBTOFRAC) & (FRACUNIT - 1));
xstep = FixedDiv(x2 - x1, abs(y2 - y1));
}
else if (yt2 < yt1)
{
mapystep = -1;
partial = (y1 >> MAPBTOFRAC) & (FRACUNIT - 1);
xstep = FixedDiv(x2 - x1, abs(y2 - y1));
}
else
{
mapystep = 0;
partial = FRACUNIT;
xstep = 256 * FRACUNIT;
}
xintercept = (x1 >> MAPBTOFRAC) + FixedMul(partial, xstep);
//
// step through map blocks
// Count is present to prevent a round off error from skipping the break
mapx = xt1;
mapy = yt1;
for (count = 0; count < 64; count++)
{
if (!P_SightBlockLinesIterator(mapx, mapy))
{
sightcounts[1]++;
return false; // early out
}
if (mapx == xt2 && mapy == yt2)
break;
if ((yintercept >> FRACBITS) == mapy)
{
yintercept += ystep;
mapx += mapxstep;
}
else if ((xintercept >> FRACBITS) == mapx)
{
xintercept += xstep;
mapy += mapystep;
}
}
//
// couldn't early out, so go through the sorted list
//
sightcounts[2]++;
return P_SightTraverseIntercepts();
}
/*
=====================
=
= P_CheckSight
=
= Returns true if a straight line between t1 and t2 is unobstructed
= look from eyes of t1 to any part of t2
=
=====================
*/
boolean P_CheckSight(mobj_t * t1, mobj_t * t2)
{
int s1, s2;
int pnum, bytenum, bitnum;
//
// check for trivial rejection
//
s1 = (t1->subsector->sector - sectors);
s2 = (t2->subsector->sector - sectors);
pnum = s1 * numsectors + s2;
bytenum = pnum >> 3;
bitnum = 1 << (pnum & 7);
if (rejectmatrix[bytenum] & bitnum)
{
sightcounts[0]++;
return false; // can't possibly be connected
}
//
// check precisely
//
sightzstart = t1->z + t1->height - (t1->height >> 2);
topslope = (t2->z + t2->height) - sightzstart;
bottomslope = (t2->z) - sightzstart;
return P_SightPathTraverse(t1->x, t1->y, t2->x, t2->y);
}