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Diffstat (limited to 'src/p_sight.c')
| -rw-r--r-- | src/p_sight.c | 352 |
1 files changed, 352 insertions, 0 deletions
diff --git a/src/p_sight.c b/src/p_sight.c new file mode 100644 index 00000000..207434ee --- /dev/null +++ b/src/p_sight.c @@ -0,0 +1,352 @@ +// Emacs style mode select -*- C++ -*- +//----------------------------------------------------------------------------- +// +// $Id: p_sight.c 4 2005-07-23 16:19:41Z fraggle $ +// +// Copyright (C) 1993-1996 by id Software, Inc. +// +// This source is available for distribution and/or modification +// only under the terms of the DOOM Source Code License as +// published by id Software. All rights reserved. +// +// The source is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License +// for more details. +// +// $Log$ +// Revision 1.1 2005/07/23 16:20:45 fraggle +// Initial revision +// +// +// DESCRIPTION: +// LineOfSight/Visibility checks, uses REJECT Lookup Table. +// +//----------------------------------------------------------------------------- + +static const char +rcsid[] = "$Id: p_sight.c 4 2005-07-23 16:19:41Z fraggle $"; + + +#include "doomdef.h" + +#include "i_system.h" +#include "p_local.h" + +// State. +#include "r_state.h" + +// +// P_CheckSight +// +fixed_t sightzstart; // eye z of looker +fixed_t topslope; +fixed_t bottomslope; // slopes to top and bottom of target + +divline_t strace; // from t1 to t2 +fixed_t t2x; +fixed_t t2y; + +int sightcounts[2]; + + +// +// P_DivlineSide +// Returns side 0 (front), 1 (back), or 2 (on). +// +int +P_DivlineSide +( fixed_t x, + fixed_t y, + divline_t* node ) +{ + fixed_t dx; + fixed_t dy; + fixed_t left; + fixed_t right; + + if (!node->dx) + { + if (x==node->x) + return 2; + + if (x <= node->x) + return node->dy > 0; + + return node->dy < 0; + } + + if (!node->dy) + { + if (x==node->y) + return 2; + + if (y <= node->y) + return node->dx < 0; + + return node->dx > 0; + } + + dx = (x - node->x); + dy = (y - node->y); + + left = (node->dy>>FRACBITS) * (dx>>FRACBITS); + right = (dy>>FRACBITS) * (node->dx>>FRACBITS); + + if (right < left) + return 0; // front side + + if (left == right) + return 2; + return 1; // back side +} + + +// +// P_InterceptVector2 +// Returns the fractional intercept point +// along the first divline. +// This is only called by the addthings and addlines traversers. +// +fixed_t +P_InterceptVector2 +( divline_t* v2, + divline_t* v1 ) +{ + fixed_t frac; + fixed_t num; + fixed_t den; + + den = FixedMul (v1->dy>>8,v2->dx) - FixedMul(v1->dx>>8,v2->dy); + + if (den == 0) + return 0; + // I_Error ("P_InterceptVector: parallel"); + + num = FixedMul ( (v1->x - v2->x)>>8 ,v1->dy) + + FixedMul ( (v2->y - v1->y)>>8 , v1->dx); + frac = FixedDiv (num , den); + + return frac; +} + +// +// P_CrossSubsector +// Returns true +// if strace crosses the given subsector successfully. +// +boolean P_CrossSubsector (int num) +{ + seg_t* seg; + line_t* line; + int s1; + int s2; + int count; + subsector_t* sub; + sector_t* front; + sector_t* back; + fixed_t opentop; + fixed_t openbottom; + divline_t divl; + vertex_t* v1; + vertex_t* v2; + fixed_t frac; + fixed_t slope; + +#ifdef RANGECHECK + if (num>=numsubsectors) + I_Error ("P_CrossSubsector: ss %i with numss = %i", + num, + numsubsectors); +#endif + + sub = &subsectors[num]; + + // check lines + count = sub->numlines; + seg = &segs[sub->firstline]; + + for ( ; count ; seg++, count--) + { + line = seg->linedef; + + // allready checked other side? + if (line->validcount == validcount) + continue; + + line->validcount = validcount; + + v1 = line->v1; + v2 = line->v2; + s1 = P_DivlineSide (v1->x,v1->y, &strace); + s2 = P_DivlineSide (v2->x, v2->y, &strace); + + // line isn't crossed? + if (s1 == s2) + continue; + + divl.x = v1->x; + divl.y = v1->y; + divl.dx = v2->x - v1->x; + divl.dy = v2->y - v1->y; + s1 = P_DivlineSide (strace.x, strace.y, &divl); + s2 = P_DivlineSide (t2x, t2y, &divl); + + // line isn't crossed? + if (s1 == s2) + continue; + + // stop because it is not two sided anyway + // might do this after updating validcount? + if ( !(line->flags & ML_TWOSIDED) ) + return false; + + // crosses a two sided line + front = seg->frontsector; + back = seg->backsector; + + // no wall to block sight with? + if (front->floorheight == back->floorheight + && front->ceilingheight == back->ceilingheight) + continue; + + // possible occluder + // because of ceiling height differences + if (front->ceilingheight < back->ceilingheight) + opentop = front->ceilingheight; + else + opentop = back->ceilingheight; + + // because of ceiling height differences + if (front->floorheight > back->floorheight) + openbottom = front->floorheight; + else + openbottom = back->floorheight; + + // quick test for totally closed doors + if (openbottom >= opentop) + return false; // stop + + frac = P_InterceptVector2 (&strace, &divl); + + if (front->floorheight != back->floorheight) + { + slope = FixedDiv (openbottom - sightzstart , frac); + if (slope > bottomslope) + bottomslope = slope; + } + + if (front->ceilingheight != back->ceilingheight) + { + slope = FixedDiv (opentop - sightzstart , frac); + if (slope < topslope) + topslope = slope; + } + + if (topslope <= bottomslope) + return false; // stop + } + // passed the subsector ok + return true; +} + + + +// +// P_CrossBSPNode +// Returns true +// if strace crosses the given node successfully. +// +boolean P_CrossBSPNode (int bspnum) +{ + node_t* bsp; + int side; + + if (bspnum & NF_SUBSECTOR) + { + if (bspnum == -1) + return P_CrossSubsector (0); + else + return P_CrossSubsector (bspnum&(~NF_SUBSECTOR)); + } + + bsp = &nodes[bspnum]; + + // decide which side the start point is on + side = P_DivlineSide (strace.x, strace.y, (divline_t *)bsp); + if (side == 2) + side = 0; // an "on" should cross both sides + + // cross the starting side + if (!P_CrossBSPNode (bsp->children[side]) ) + return false; + + // the partition plane is crossed here + if (side == P_DivlineSide (t2x, t2y,(divline_t *)bsp)) + { + // the line doesn't touch the other side + return true; + } + + // cross the ending side + return P_CrossBSPNode (bsp->children[side^1]); +} + + +// +// P_CheckSight +// Returns true +// if a straight line between t1 and t2 is unobstructed. +// Uses REJECT. +// +boolean +P_CheckSight +( mobj_t* t1, + mobj_t* t2 ) +{ + int s1; + int s2; + int pnum; + int bytenum; + int bitnum; + + // First check for trivial rejection. + + // Determine subsector entries in REJECT table. + s1 = (t1->subsector->sector - sectors); + s2 = (t2->subsector->sector - sectors); + pnum = s1*numsectors + s2; + bytenum = pnum>>3; + bitnum = 1 << (pnum&7); + + // Check in REJECT table. + if (rejectmatrix[bytenum]&bitnum) + { + sightcounts[0]++; + + // can't possibly be connected + return false; + } + + // An unobstructed LOS is possible. + // Now look from eyes of t1 to any part of t2. + sightcounts[1]++; + + validcount++; + + sightzstart = t1->z + t1->height - (t1->height>>2); + topslope = (t2->z+t2->height) - sightzstart; + bottomslope = (t2->z) - sightzstart; + + strace.x = t1->x; + strace.y = t1->y; + t2x = t2->x; + t2y = t2->y; + strace.dx = t2->x - t1->x; + strace.dy = t2->y - t1->y; + + // the head node is the last node output + return P_CrossBSPNode (numnodes-1); +} + + |