ref: 0774dce204c2c01622c59819e2a29590a1b50e46
dir: /src/heretic/p_sight.c/
// P_sight.c
#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 = MAXINT;
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 = MAXINT;
}
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 );
}