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slide.c
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slide.c
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#include "Doom.h"
#include <IntMath.h>
#define CLIPRADIUS 23
#define SIDE_ON 0
#define SIDE_FRONT 1
#define SIDE_BACK -1
Fixed slidex, slidey; // the final position
line_t *specialline;
static Fixed slidedx, slidedy; // current move for completablefrac
static Fixed endbox[4]; // final proposed position
static Fixed blockfrac; // the fraction of move that gets completed
static Fixed blocknvx, blocknvy; // the vector of the line that blocks move
// p1, p2 are line endpoints
// p3, p4 are move endpoints
static int p1x, p1y, p2x, p2y, p3x, p3y, p4x, p4y;
static Fixed nvx, nvy; // normalized line vector
static mobj_t *slidething;
static int SL_PointOnSide2 (int x1, int y1, int x2, int y2, int x3, int y3)
{
int nx, ny;
int dist;
x1 = (x1-x2);
y1 = (y1-y2);
nx = (y3-y2);
ny = (x2-x3);
dist = IMFixMul(x1,nx);
dist += IMFixMul(y1,ny);
if (dist < 0)
return SIDE_BACK;
return SIDE_FRONT;
}
/*
===================
=
= P_SlideMove
=
===================
*/
void P_SlideMove (mobj_t *mo)
{
Fixed dx, dy;
Fixed rx, ry;
int i;
Fixed frac, slide;
slidething = mo;
dx = slidething->momx;
dy = slidething->momy;
slidex = slidething->x;
slidey = slidething->y;
// perform a maximum of three bumps
for (i=0 ; i<3 ; i++) {
frac = P_CompletableFrac (dx,dy);
if (frac != 0x10000)
frac -= 0x1000;
if (frac < 0)
frac = 0;
rx = IMFixMul(frac,dx);
ry = IMFixMul(frac,dy);
slidex += rx;
slidey += ry;
//
// made it the entire way
//
if (frac == 0x10000) {
slidething->momx = dx;
slidething->momy = dy;
SL_CheckSpecialLines (slidething->x, slidething->y
, slidex, slidey);
return;
}
//
// project the remaining move along the line that blocked movement
//
dx -= rx;
dy -= ry;
slide = IMFixMul(dx,blocknvx);
slide += IMFixMul(dy,blocknvy);
dx = IMFixMul(slide,blocknvx);
dy = IMFixMul(slide,blocknvy);
}
//
// some hideous situation has happened that won't let the player slide
//
slidex = slidething->x;
slidey = slidething->y;
slidething->momx = slidething->momy = 0;
}
/*
===================
=
= P_CompletableFrac
=
= Returns the fraction of the move that is completable
===================
*/
Fixed P_CompletableFrac(Fixed dx,Fixed dy)
{
int xl,xh,yl,yh,bx,by;
blockfrac = 0x10000; // the entire dist until shown otherwise
slidedx = dx;
slidedy = dy;
endbox[BOXTOP] = slidey + CLIPRADIUS*FRACUNIT;
endbox[BOXBOTTOM] = slidey - CLIPRADIUS*FRACUNIT;
endbox[BOXRIGHT] = slidex + CLIPRADIUS*FRACUNIT;
endbox[BOXLEFT] = slidex - CLIPRADIUS*FRACUNIT;
if (dx > 0)
endbox[BOXRIGHT] += dx;
else
endbox[BOXLEFT] += dx;
if (dy > 0)
endbox[BOXTOP] += dy;
else
endbox[BOXBOTTOM] += dy;
++validcount;
//
// check lines
//
xl = (endbox[BOXLEFT] - BlockMapOrgX)>>MAPBLOCKSHIFT;
xh = (endbox[BOXRIGHT] - BlockMapOrgX)>>MAPBLOCKSHIFT;
yl = (endbox[BOXBOTTOM] - BlockMapOrgY)>>MAPBLOCKSHIFT;
yh = (endbox[BOXTOP] - BlockMapOrgY)>>MAPBLOCKSHIFT;
if (xl<0)
xl = 0;
if (yl<0)
yl = 0;
if (xh>=BlockMapWidth)
xh = BlockMapWidth-1;
if (yh>=BlockMapHeight)
yh = BlockMapHeight-1;
for (bx=xl ; bx<=xh ; bx++)
for (by=yl ; by<=yh ; by++) {
BlockLinesIterator(bx,by,SL_CheckLine);
}
//
// examine results
//
if (blockfrac < 0x1000)
{
blockfrac = 0;
specialline = 0; // can't cross anything on a bad move
return 0; // solid wall or thing
}
return blockfrac;
}
int SL_PointOnSide (int x, int y)
{
int dx, dy, dist;
dx = x - p1x;
dy = y - p1y;
dist = IMFixMul(dx,nvx);
dist += IMFixMul(dy,nvy);
if (dist > FRACUNIT)
return SIDE_FRONT;
if (dist < -FRACUNIT)
return SIDE_BACK;
return SIDE_ON;
}
Fixed SL_CrossFrac (void)
{
int dx, dy, dist1, dist2, frac;
// project move start and end points onto line normal
dx = p3x - p1x;
dy = p3y - p1y;
dist1 = IMFixMul(dx,nvx);
dist1 += IMFixMul(dy,nvy);
dx = p4x - p1x;
dy = p4y - p1y;
dist2 = IMFixMul(dx,nvx);
dist2 += IMFixMul(dy,nvy);
if ( (dist1 < 0) == (dist2 < 0) )
return FRACUNIT; // doesn't cross
frac = IMFixDiv(dist1, dist1 - dist2 );
return frac;
}
Boolean CheckLineEnds (void)
{
int snx, sny; // sight normals
int dist1, dist2;
int dx, dy;
snx = p4y-p3y;
sny = -(p4x-p3x);
dx = p1x - p3x;
dy = p1y - p3y;
dist1 = IMFixMul(dx,snx);
dist1 += IMFixMul(dy,sny);
dx = p2x - p3x;
dy = p2y - p3y;
dist2 = IMFixMul(dx,snx);
dist2 += IMFixMul(dy,sny);
if ( (dist1<0) == (dist2<0) )
return TRUE;
return FALSE;
}
/*
====================
=
= ClipToLine
=
= Call with p1 and p2 set to the endpoints
= and nvx, nvy set to normalized vector
= Assumes the start point is definately on the front side of the line
= returns the fraction of the current move that crosses the line segment
====================
*/
void ClipToLine ( void )
{
Fixed frac;
int side2, side3;
//
// adjust start so it will be the first point contacted on the player
// circle
//
// p3, p4 are move endpoints
p3x = slidex - CLIPRADIUS*nvx;
p3y = slidey - CLIPRADIUS*nvy;
p4x = p3x + slidedx;
p4y = p3y + slidedy;
//
// if the adjusted point is on the other side of the line, the endpoint
// must be checked
//
side2 = SL_PointOnSide (p3x, p3y);
if (side2 == SIDE_BACK)
{
return; // !!! ClipToPoint and slide along normal to line
}
side3 = SL_PointOnSide (p4x, p4y);
if (side3 == SIDE_ON)
return; // the move goes flush with the wall
if (side3 == SIDE_FRONT)
return; // moves doesn't cross line
if (side2 == SIDE_ON)
{
frac = 0; // moves towards the line
goto blockmove;
}
//
// the line endpoints must be on opposite sides of the move trace
//
//
// find the fractional intercept
//
frac = SL_CrossFrac ();
if (frac < blockfrac)
{
blockmove:
blockfrac = frac;
blocknvx = -nvy;
blocknvy = nvx;
}
}
/*
==================
=
= SL_CheckLine
=
==================
*/
Word SL_CheckLine(line_t *ld)
{
Fixed opentop, openbottom;
sector_t *front, *back;
int side1, temp;
// check bbox first
if (endbox[BOXRIGHT] < ld->bbox[BOXLEFT]
|| endbox[BOXLEFT] > ld->bbox[BOXRIGHT]
|| endbox[BOXTOP] < ld->bbox[BOXBOTTOM]
|| endbox[BOXBOTTOM] > ld->bbox[BOXTOP] )
return TRUE;
// see if it can possibly block movement
if (!ld->backsector || ld->flags & ML_BLOCKING)
goto findfrac; // explicitly blocking
front = ld->frontsector;
back = ld->backsector;
if (front->floorheight > back->floorheight)
openbottom = front->floorheight;
else
openbottom = back->floorheight;
if (openbottom - slidething->z > 24*FRACUNIT)
goto findfrac; // too big of a step up
if (front->ceilingheight < back->ceilingheight)
opentop = front->ceilingheight;
else
opentop = back->ceilingheight;
if (opentop - openbottom >= 56*FRACUNIT)
return TRUE; // the line doesn't block movement
// the line definately blocks movement
findfrac:
// p1, p2 are line endpoints
p1x = ld->v1.x;
p1y = ld->v1.y;
p2x = ld->v2.x;
p2y = ld->v2.y;
nvx = finesine[ld->fineangle];
nvy = -finecosine[ld->fineangle];
side1 = SL_PointOnSide (slidex, slidey);
if (side1 == SIDE_ON)
return TRUE;
if (side1 == SIDE_BACK)
{
if (!ld->backsector)
return TRUE; // don't clip to backs of one sided lines
temp = p1x;
p1x = p2x;
p2x = temp;
temp = p1y;
p1y = p2y;
p2y = temp;
nvx = -nvx;
nvy = -nvy;
}
ClipToLine ();
return TRUE;
}
static line_t **list;
static line_t *ld;
void SL_CheckSpecialLines (int x1, int y1, int x2, int y2)
{
int bx, by, xl, xh, yl, yh, bxl, bxh, byl, byh;
int x3,y3,x4,y4;
int side1, side2;
if (x1<x2) {
xl = x1;
xh = x2;
} else {
xl = x2;
xh = x1;
}
if (y1<y2) {
yl = y1;
yh = y2;
} else {
yl = y2;
yh = y1;
}
bxl = (xl - BlockMapOrgX)>>MAPBLOCKSHIFT;
bxh = (xh - BlockMapOrgX)>>MAPBLOCKSHIFT;
byl = (yl - BlockMapOrgY)>>MAPBLOCKSHIFT;
byh = (yh - BlockMapOrgY)>>MAPBLOCKSHIFT;
if (bxl<0)
bxl = 0;
if (byl<0)
byl = 0;
if (bxh>=BlockMapWidth)
bxh = BlockMapWidth-1;
if (byh>=BlockMapHeight)
byh = BlockMapHeight-1;
specialline = 0;
++validcount;
for (bx=bxl ; bx<=bxh ; bx++)
for (by=byl ; by<=byh ; by++) {
for ( list = BlockMapLines[(by*BlockMapWidth)+bx] ;list[0];++list) {
ld = list[0];
if (!ld->special)
continue;
if (ld->validcount == validcount)
continue; // line has already been checked
ld->validcount = validcount;
if (xh < ld->bbox[BOXLEFT]
|| xl > ld->bbox[BOXRIGHT]
|| yh < ld->bbox[BOXBOTTOM]
|| yl > ld->bbox[BOXTOP] )
continue;
x3 = ld->v1.x;
y3 = ld->v1.y;
x4 = ld->v2.x;
y4 = ld->v2.y;
side1 = SL_PointOnSide2 (x1,y1, x3,y3, x4,y4);
side2 = SL_PointOnSide2 (x2,y2, x3,y3, x4,y4);
if (side1 == side2)
continue; // move doesn't cross line
side1 = SL_PointOnSide2 (x3,y3, x1,y1, x2,y2);
side2 = SL_PointOnSide2 (x4,y4, x1,y1, x2,y2);
if (side1 == side2)
continue; // line doesn't cross move
specialline = ld;
return;
}
}
}