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quakeforge/libs/models/trace.c
Bill Currie 9f32004599 Add a fixme. 
I've had enough of this for the moment, but I'm pretty sure the test needs
some more consideration, and I'll probably forget about it if I don't mark
it.
2011-12-07 17:27:13 +09:00

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/*
trace.c
BSP line tracing
Copyright (C) 2004 Bill Currie
Author: Bill Currie <bill@taniwha.org>
Date: 2004/9/25
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.
You should have received a copy of the GNU General Public License
along with this program; if not, write to:
Free Software Foundation, Inc.
59 Temple Place - Suite 330
Boston, MA 02111-1307, USA
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
static __attribute__ ((used)) const char rcsid[] =
"$Id$";
#ifdef HAVE_STRING_H
# include <string.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif
#include "QF/model.h"
#include "QF/sys.h"
#include "QF/winding.h"
#include "compat.h"
#include "world.h"
/* LINE TESTING IN HULLS */
// 1/32 epsilon to keep floating point happy
#ifndef DIST_EPSILON
#define DIST_EPSILON (0.03125)
#endif
#define PLANE_EPSILON (0.001)
typedef struct {
plane_t planes[3];
winding_t points[3];
winding_t edges[3];
clipport_t portals[3];
} clipbox_t;
typedef struct {
qboolean seen_empty;
qboolean seen_solid;
qboolean moved;
plane_t *split_plane;
vec3_t dist;
const vec_t *origin;
const vec_t *start_point;
const vec_t *end_point;
clipbox_t box;
} trace_state_t;
typedef struct {
vec3_t start;
vec3_t end;
vec_t start_frac;
int side;
int num;
plane_t *plane;
} tracestack_t;
static void
fast_norm (vec3_t v)
{
vec_t m;
m = fabs (v[0]) + fabs (v[1]) + fabs (v[2]);
VectorScale (v, 1 / m, v);
}
/** Initialize the clipbox representing the faces that might hit the portal.
When a box is moving, at most three of its faces might hit the portal.
Those faces all face such that the dot product of their normal and the
box's velocity is positive (ie, n.v > 0). When the motion is in an axial
plane, only two faces might hit. For axial motion, only one face.
The faces are set up such that the first point of each winding is the
leading corner of the box, and the edges are set up such that testing
only the first three edges of each winding covers all nine edges (ie,
the forth edge of one face is the reverse of the first edge of the next
face).
The windings are clockwise when looking down the face's normal (ie, when
looking at the front of the face).
*/
static void
init_box (const trace_t *trace, clipbox_t *box, const vec3_t vel)
{
vec3_t p;
int u[3];
int i, j, k;
vec_t s[2] = {1, -1};
//FIXME rotated box
for (i = 0; i < 3; i++)
u[i] = (vel[i] >= 0 ? 1 : -1);
Vector3Scale (u, trace->extents, p);
for (i = 0; i < 3; i++) {
box->portals[i].planenum = i;
box->portals[i].next[0] = 0;
box->portals[i].next[0] = 0;
box->portals[i].leafs[0] = 0;
box->portals[i].leafs[0] = 0;
box->portals[i].winding = &box->points[i];
box->portals[i].edges = &box->edges[i];
VectorZero (box->planes[i].normal);
box->planes[i].normal[i] = u[i];
box->planes[i].dist = DotProduct (p, box->planes[i].normal);
box->planes[i].type = i;
box->points[i].numpoints = 4;
box->edges[i].numpoints = 4;
VectorCopy (u, box->points[i].points[0]);
VectorZero (box->edges[i].points[0]);
j = (i + (u[0]*u[1]*u[2] + 3) / 2) % 3;
box->edges[i].points[0][j] = -u[j];
for (j = 1; j < 4; j++) {
box->points[i].points[j][i] = box->points[i].points[j - 1][i];
box->edges[i].points[j][i] = box->edges[i].points[j - 1][i];
for (k = 0; k < 2; k++) {
int a, b;
a = (i + 1 + k) % 3;
b = (i + 2 - k) % 3;
box->points[i].points[j][a]
= s[k] * u[i] * box->points[i].points[j - 1][b];
box->edges[i].points[j][a]
= s[k] * u[i] * box->edges[i].points[j - 1][b];
}
Vector3Scale (box->points[i].points[j - 1], trace->extents,
box->points[i].points[j - 1]);
Vector3Scale (box->edges[i].points[j - 1], trace->extents,
box->edges[i].points[j - 1]);
VectorScale (box->edges[i].points[j - 1], 2,
box->edges[i].points[j - 1]);
}
Vector3Scale (box->points[i].points[3], trace->extents,
box->points[i].points[3]);
Vector3Scale (box->edges[i].points[3], trace->extents,
box->edges[i].points[3]);
VectorScale (box->edges[i].points[3], 2,
box->edges[i].points[3]);
}
}
static inline float
calc_offset (const trace_t *trace, const plane_t *plane)
{
vec_t d = 0;
vec3_t Rn;
//FIXME rotated box/ellipsoid
switch (trace->type) {
case tr_point:
break;
case tr_box:
if (plane->type < 3)
d = trace->extents[plane->type];
else
d = (fabs (trace->extents[0] * plane->normal[0])
+ fabs (trace->extents[1] * plane->normal[1])
+ fabs (trace->extents[2] * plane->normal[2]));
break;
case tr_ellipsoid:
VectorSet (trace->extents[0] * plane->normal[0],
trace->extents[1] * plane->normal[1],
trace->extents[2] * plane->normal[2], Rn);
d = sqrt(DotProduct (Rn, Rn)); //FIXME no sqrt
break;
}
return d;
}
static qboolean
point_inside_portal (const clipport_t *portal, const plane_t *plane,
const vec3_t p)
{
vec3_t x, c;
const vec_t *n = plane->normal;
int i;
const winding_t *points = portal->winding;
const winding_t *edges = portal->edges;
for (i = 0; i < points->numpoints; i++) {
VectorSubtract (p, points->points[i], x);
CrossProduct (x, edges->points[i], c);
if (DotProduct (c, c) < PLANE_EPSILON)
return false;
if (DotProduct (c, n) <= 0)
return false;
}
return true;
}
static qboolean
edges_intersect (const vec3_t p1, const vec3_t p2,
const vec3_t r1, const vec3_t r2)
{
vec3_t p, r, b;
vec3_t p_r, b_p, b_r;
vec_t tp, tr, den;
VectorSubtract (p2, p1, p);
VectorSubtract (r2, r1, r);
VectorSubtract (r1, p1, b);
CrossProduct (p, r, p_r);
if (VectorIsZero (p_r))
return false;
CrossProduct (b, p, b_p);
CrossProduct (b, r, b_r);
tr = DotProduct (b_p, p_r);
tp = DotProduct (b_r, p_r);
den = DotProduct (p_r, p_r);
if ((tr < 0 || tr > den) || (tp < 0 || tp > den))
return false;
return true;
}
static qboolean
trace_hits_portal (const hull_t *hull, const trace_t *trace,
clipport_t *portal, const vec3_t start, const vec3_t vel)
{
int i;
vec_t *point;
vec_t *edge;
vec_t dist, offset, vn;
plane_t *plane;
plane_t cutplane;
plane = hull->planes + portal->planenum;
vn = DotProduct (vel, plane->normal);
cutplane.type = 3; // generic plane
for (i = 0; i < portal->winding->numpoints; i++) {
point = portal->winding->points[i];
edge = portal->edges->points[i];
// so long as the plane distance and offset are calculated using
// the same normal vector, the normal vector length does not
// matter.
CrossProduct (vel, edge, cutplane.normal);
fast_norm (cutplane.normal);
cutplane.dist = DotProduct (cutplane.normal, point);
dist = PlaneDiff (start, &cutplane);
offset = calc_offset (trace, &cutplane);
if ((vn > 0 && dist >= offset - PLANE_EPSILON)
|| (vn < 0 && dist <= -offset + PLANE_EPSILON))
return false;
}
return true;
}
static qboolean
trace_enters_leaf (hull_t *hull, trace_t *trace, clipleaf_t *leaf,
plane_t *plane, const vec3_t vel, const vec3_t org)
{
clipport_t *portal;
int side;
int planenum;
vec_t v_n;
planenum = plane - hull->planes;
v_n = DotProduct (vel, plane->normal);
if (!v_n) {
//FIXME is this correct? The assumption is that if we got to a leaf
//travelliing parallel to its plane, then we have to be in the leaf
return true;
}
for (portal = leaf->portals; portal; portal = portal->next[side]) {
side = portal->leafs[1] == leaf;
if (portal->planenum != planenum)
continue;
if (trace_hits_portal (hull, trace, portal, org, vel))
return true;
}
return false;
}
static vec_t
edge_portal_dist (const plane_t *plane, const clipport_t *portal,
const vec3_t p1, const vec3_t p2, const vec3_t vel)
{
int i;
winding_t *winding = portal->winding;
winding_t *edges = portal->edges;
// check for edge point hitting portal face
{
vec_t t1, t2, vn;
vn = DotProduct (vel, plane->normal);
t1 = PlaneDiff (p1, plane);
t2 = PlaneDiff (p2, plane);
// ensure p1 is the closest point to the plane
if ((0 < t2 && t2 < t1)
|| (0 > t2 && t2 > t1)) {
// p2 is closer to the plane, so swap the points and times
const vec_t *r = p2;
vec_t t = t2;
t2 = t1; t1 = t;
p2 = p1; p1 = r;
}
if (vn * t1 > 0) {
// the edge is travelling away from the portal's plane
return 1;
}
// if t1 * t2 < 0, the points straddle the portal's plane and the
// nearest point test can be skipped
if (vn && t1 * t2 > 0) { //FIXME epsilon
vec3_t x, c;
vec3_t imp;
t1 /= vn;
if (t1 <= -1) {
// the edge doesn't make it as far as the portal's plane
return 1;
}
VectorMultSub (p1, t1, vel, imp);
for (i = 0; i < winding->numpoints; i++) {
VectorSubtract (imp, winding->points[i], x);
CrossProduct (x, edges->points[i], c);
if (DotProduct (c, plane->normal) < 0)
break; // miss
}
if (i == winding->numpoints) {
// the closer end of the edge hit the portal, so -t1 is the
// fraction
return -t1;
}
// the closer end of the edge missed the portal, check the farther
// end, but only with this portal edge.
VectorMultSub (p2, t2 / vn, vel, imp);
VectorSubtract (imp, winding->points[i], x);
CrossProduct (x, edges->points[i], c);
if (DotProduct (c, plane->normal) < 0) {
// both impacts are on the outside of this portal edge, so the
// edge being tested misses the portal
return 1;
}
// the two impact points are on both sides of a portal edge, so the
// edge being tested might hit a portal edge rather than the portal
// face
}
}
{
vec3_t e;
vec_t frac = 1.0;
plane_t ep;
// set up the plane through which the edge travels
VectorSubtract (p2, p1, e);
CrossProduct (e, vel, ep.normal);
ep.dist = DotProduct (p1, ep.normal);
ep.type = 3;
for (i = 0; i < winding->numpoints; i++) {
vec_t t, vn;
const vec_t *r = winding->points[i];
const vec_t *v = edges->points[i];
vec3_t x, y;
vn = DotProduct (v, ep.normal);
if (!vn) // FIXME epsilon
continue; // portal edge is parallel to the plane
t = PlaneDiff (r, &ep) / vn;
if (t < -1 || t > 0)
continue; // portal edge does not reach the plane
// impact point of portal edge with the plane
VectorMultSub (r, t, v, x);
// project the impact point back to the edge along the velocity
VectorSubtract (x, p1, y);
t = DotProduct (y, vel) / DotProduct (vel, vel);
VectorMultSub (x, t, vel, y);
VectorSubtract (y, p1, y);
t = DotProduct (y, y) / DotProduct (e, y);
if (t < 0 || t > 1)
continue; // the edge misses the portal edge
VectorMultAdd (p1, t, e, y);
VectorSubtract (x, y, y);
t = DotProduct (y, vel) / DotProduct (vel, vel);
if (t < 0 || t >= frac)
continue; // this is not the nearest edge pair
// the edges hit, and they are the closes edge pair so far
frac = t;
}
return frac;
}
}
static vec_t
box_portal_dist (const hull_t *hull, const clipport_t *portal,
const trace_state_t *state)
{
vec3_t nvel;
plane_t *plane = hull->planes + portal->planenum;
int i, j;
vec_t frac, t;
vec3_t p1, p2;
const clipbox_t *box = &state->box;
const vec_t *start = state->start_point;
const vec_t *vel = state->dist;
frac = 1.0;
for (i = 0; i < 3; i++) {
// all faces on box have 4 points (and edges), but we need test only
// three on each face
for (j = 0; j < 3; j++) {
VectorAdd (box->points[i].points[j], start, p1);
VectorAdd (box->points[i].points[j + 1], start, p2);
t = edge_portal_dist (plane, portal, p1, p2, vel);
if (t < frac)
frac = t;
}
}
VectorNegate (vel, nvel);
for (i = 0; i < portal->winding->numpoints; i++) {
j = i + 1;
if (j >= portal->winding->numpoints)
j -= portal->winding->numpoints;
VectorSubtract (portal->winding->points[i], start, p1);
VectorSubtract (portal->winding->points[j], start, p2);
for (j = 0; j < 3; j++) {
const clipport_t *p = &box->portals[j];
t = edge_portal_dist (box->planes + p->planenum, p, p1, p2, nvel);
if (t < frac)
frac = t;
}
}
return frac;
}
static inline void
calc_impact (hull_t *hull, trace_t *trace, trace_state_t *state,
clipleaf_t *leaf)
{
vec_t t1, t2, frac, offset;
t1 = PlaneDiff (state->start_point, state->split_plane);
t2 = PlaneDiff (state->end_point, state->split_plane);
offset = calc_offset (trace, state->split_plane);
if (t1 < 0) {
frac = (t1 + offset + DIST_EPSILON) / (t1 - t2);
// invert plane paramterers
} else {
frac = (t1 - offset - DIST_EPSILON) / (t1 - t2);
}
frac = bound (0, frac, 1);
if (leaf && trace->type != tr_point) {
int i;
int side;
int planenum;
clipport_t *portal;
vec3_t impact;
planenum = state->split_plane - hull->planes;
VectorMultAdd (state->start_point, frac, state->dist, impact);
if (DotProduct (state->dist, state->split_plane->normal) > 0)
VectorMultAdd (impact, offset, state->split_plane->normal, impact);
else
VectorMultSub (impact, offset, state->split_plane->normal, impact);
for (portal = leaf->portals; portal; portal = portal->next[side]) {
side = portal->leafs[1] == leaf;
if (portal->planenum != planenum)
continue;
for (i = 0; i < portal->winding->numpoints; i++) {
vec3_t r, s;
VectorSubtract (impact, portal->winding->points[i], r);
CrossProduct (r, portal->edges->points[i], s);
if (DotProduct (s, state->split_plane->normal) > 0)
continue; // "hit"
break; // "miss";
}
if (i == portal->winding->numpoints)
goto finish_impact; // impact with the face of the polygon
}
frac = 1.0;
for (portal = leaf->portals; portal; portal = portal->next[side]) {
vec_t t;
side = portal->leafs[1] == leaf;
if (portal->planenum != planenum)
continue;
t = box_portal_dist (hull, portal, state);
if (t < frac)
frac = t;
}
}
finish_impact:
if (frac < trace->fraction) {
trace->fraction = frac;
VectorMultAdd (state->start_point, frac, state->dist, trace->endpos);
if (t1 < 0) {
// invert plane paramterers
VectorNegate (state->split_plane->normal, trace->plane.normal);
trace->plane.dist = -state->split_plane->dist;
} else {
VectorCopy (state->split_plane->normal, trace->plane.normal);
trace->plane.dist = state->split_plane->dist;
}
}
}
static qboolean
portal_intersect (trace_t *trace, clipport_t *portal, plane_t *plane,
const vec3_t origin)
{
vec3_t r;
vec_t o_n;
int i;
static vec3_t verts[][2] = {
{{ -1, -1, -1}, { 1, -1, -1}},
{{ -1, -1, 1}, { 1, -1, 1}},
{{ -1, 1, -1}, { 1, 1, -1}},
{{ -1, 1, 1}, { 1, 1, 1}},
{{ -1, -1, -1}, { -1, 1, -1}},
{{ 1, -1, -1}, { 1, 1, -1}},
{{ -1, -1, 1}, { -1, 1, 1}},
{{ 1, -1, 1}, { 1, 1, 1}},
{{ -1, -1, -1}, { -1, -1, 1}},
{{ -1, 1, -1}, { -1, 1, 1}},
{{ 1, -1, -1}, { 1, -1, 1}},
{{ 1, 1, -1}, { 1, 1, 1}},
};
// if any portal point is inside or touches the box, then they intersect
for (i = 0; i < portal->winding->numpoints; i++) {
VectorSubtract (portal->winding->points[i], origin, r);
if (fabs(r[0]) <= trace->extents[0]
&& fabs(r[1]) <= trace->extents[1]
&& fabs(r[2]) <= trace->extents[2])
return true;
}
// if any box edge crosses or touches the plane within the portal, then
// they intersect
o_n = DotProduct (origin, plane->normal);
for (i = 0; i < 12; i++) {
vec3_t p1, p2, imp, dist;
vec_t t1, t2, frac;
Vector3Scale (trace->extents, verts[i][0], p1);
Vector3Scale (trace->extents, verts[i][1], p2);
t1 = PlaneDiff (p1, plane) + o_n;
t2 = PlaneDiff (p2, plane) + o_n;
// if both ends of the box edge are on the same side (or touching) the
// plane, the edge does not cross the plane
// if only one end of the edge is touching, then we still have to
// check the impact point.
if ((t1 > 0 && t2 > 0) || (t1 < 0 && t2 < 0) || (t1 == t2))
continue;
if (t1 == t2) {
int j;
// the edge is on the plane
// if either end touches the portal, then the box and portal touch
if (point_inside_portal (portal, plane, p1))
return true;
if (point_inside_portal (portal, plane, p2))
return true;
// if the edge intersects with a portal edge, then the box and
// portal touch
for (j = 0; j < portal->winding->numpoints; j++) {
int k = j + 1;
if (k == portal->winding->numpoints)
k = 0;
if (edges_intersect (p1, p2, portal->winding->points[j],
portal->winding->points[k]))
return true;
}
continue;
}
// since t1 and t2 are guaranteed to be on opposite sides of the plane,
// or only one touching, they are guaranteed to be unequal. Also, frac
// is guaranteed to be between 0 and 1
frac = t1 / (t1 - t2);
VectorSubtract (p2, p1, dist);
VectorMultAdd (p1, frac, dist, imp);
VectorAdd (imp, origin, imp);
if (point_inside_portal (portal, plane, imp)) {
// the impact point is in the portal
return true;
}
}
return 0;
}
static int test_count;
static int
trace_contents (hull_t *hull, trace_t *trace, clipleaf_t *leaf,
const vec3_t origin)
{
clipport_t *portal;
int side;
int contents = leaf->contents;
leaf->test_count = test_count;
// set the auxiliary contents data. this is a bit field of all contents
// types contained within the trace.
// contents start at -1 (empty). bit 0 represents CONTENTS_EMPTY
trace->contents |= 1 << (~contents);
// check all adjoining leafs that contain part of the trace
for (portal = leaf->portals; portal; portal = portal->next[side]) {
vec_t offset;
vec_t dist;
plane_t *plane;
int res;
clipleaf_t *l;
side = portal->leafs[1] == leaf;
l = portal->leafs[side ^ 1];
if (l->test_count == test_count)
continue;
plane = hull->planes + portal->planenum;
dist = PlaneDiff (origin, plane);
offset = calc_offset (trace, plane);
// the side of the plane on which we are does not matter, only
// whether we're crossing the plane. merely touching the plane does
// not cause us to cross it
if (fabs (dist) >= offset - PLANE_EPSILON)
continue;
if (!portal_intersect (trace, portal, plane, origin))
continue;
res = trace_contents (hull, trace, l, origin);
//FIXME better test?
// solid > lava > slime > water > empty (desired)
// solid > current (good)
// problem is, current > sky > lava (what is best?)
if (res == CONTENTS_SOLID
|| (contents != CONTENTS_SOLID && res < contents))
contents = res;
}
return contents;
}
static vec_t
trace_to_leaf (const hull_t *hull, clipleaf_t *leaf,
const trace_t *trace, const trace_state_t *state, vec3_t stop)
{
clipport_t *portal;
plane_t *plane;
int side;
vec_t frac = 1;
vec_t t1, t2, offset, f;
qboolean clipped = false;
clipleaf_t *l;
trace_state_t lstate = *state;
leaf->test_count = test_count;
for (portal = leaf->portals; portal; portal = portal->next[side]) {
side = portal->leafs[1] == leaf;
plane = hull->planes + portal->planenum;
if (plane == state->split_plane)
continue;
if (!trace_hits_portal (hull, trace, portal,
state->start_point, state->dist))
continue;
l = portal->leafs[side^1];
if (l->test_count == test_count)
continue;
//FIXME the decision on whether to recurse needs to be reviewed
t1 = PlaneDiff (state->start_point, plane);
t2 = PlaneDiff (state->end_point, plane);
offset = calc_offset (trace, plane);
f = (t1 + (t1 < 0 ? offset : -offset)) / (t1 - t2);
if (f < 0 && l->contents != CONTENTS_SOLID
&& l->test_count != test_count) {
f = trace_to_leaf (hull, l, trace, state, 0);
} else {
lstate.split_plane = plane;
f = box_portal_dist (hull, portal, &lstate);
}
if (f >= 0) {
clipped = true;
if (f < frac)
frac = f;
}
}
//printf ("%d %g\n", clipped, frac);
if (!clipped)
frac = 0;
if (stop)
VectorMultAdd (state->start_point, frac, state->dist, stop);
return frac;
}
static int
visit_leaf (hull_t *hull, int num, clipleaf_t *leaf, trace_t *trace,
trace_state_t *state)
{
int contents;
// it's not possible to not be in the leaf when doing a point trace
if (trace->type != tr_point) {
vec3_t origin;
// if split_plane is null, the trace did not cross the last node plane
if (state->split_plane
&& !trace_enters_leaf (hull, trace, leaf, state->split_plane,
state->dist, state->origin))
return 0; // we're not here
contents = leaf->contents;
if (contents != CONTENTS_SOLID) {
//FIXME this is probably slow
test_count++;
trace_to_leaf (hull, leaf, trace, state, origin);
//printf ("(%g %g %g) (%g %g %g)\n",
//VectorExpand (state->start_point), VectorExpand (origin));
test_count++;
trace->contents = 0;
contents = trace_contents (hull, trace, leaf, origin);
//printf ("%d\n", contents);
}
} else {
contents = num;
}
if (contents == CONTENTS_SOLID) {
if (!state->seen_empty && !state->seen_solid) {
// this is the first leaf visited, thus the start leaf
trace->startsolid = state->seen_solid = true;
} else if (!state->seen_empty && state->seen_solid) {
// If crossing from one solid leaf to another, treat the
// whole trace as solid (this is what id does).
// However, since allsolid is initialized to true, no need
// to do anything.
if (state->moved)
return 1;
} else {
// crossing from an empty leaf to a solid leaf: the trace
// has collided.
if (state->split_plane) {
calc_impact (hull, trace, state, leaf);
} else {
// if there's no split plane, then there is no impact
trace->fraction = 1.0;
}
if (trace->type == tr_point)
return 1;
}
} else {
state->seen_empty = true;
trace->allsolid = false;
if (contents == CONTENTS_EMPTY)
trace->inopen = true;
else
trace->inwater = true;
}
return 0;
}
VISIBLE void
MOD_TraceLine (hull_t *hull, int num,
const vec3_t start_point, const vec3_t end_point,
trace_t *trace)
{
vec_t start_dist, end_dist, frac[2], offset;
vec3_t start, end, dist;
int side;
tracestack_t *tstack;
tracestack_t tracestack[256];
mclipnode_t *node;
plane_t *plane;
clipleaf_t *leaf;
trace_state_t trace_state;
VectorCopy (start_point, start);
VectorCopy (end_point, end);
VectorSubtract (end, start, trace_state.dist);
tstack = tracestack;
trace_state.start_point = start_point;
trace_state.end_point = end_point;
trace_state.origin = start;
trace_state.seen_empty = false;
trace_state.seen_solid = false;
trace_state.moved = false;
trace_state.split_plane = 0;
init_box (trace, &trace_state.box, trace_state.dist);
leaf = 0;
plane = 0;
trace->allsolid = true;
trace->startsolid = false;
trace->inopen = false;
trace->inwater = false;
trace->fraction = 1.0;
while (1) {
while (num < 0) {
if (visit_leaf (hull, num, leaf, trace, &trace_state))
return;
// pop up the stack for a back side
do {
if (tstack-- == tracestack) {
// we've finished.
return;
}
} while (tstack->start_frac > trace->fraction);
// go down the back side
VectorCopy (tstack->start, start);
VectorCopy (tstack->end, end);
side = tstack->side;
trace_state.split_plane = tstack->plane;
trace_state.moved = tstack->start_frac > 0;
if (hull->nodeleafs)
leaf = hull->nodeleafs[tstack->num].leafs[side ^ 1];
num = hull->clipnodes[tstack->num].children[side ^ 1];
}
//printf ("%d\n", num);
node = hull->clipnodes + num;
plane = hull->planes + node->planenum;
start_dist = PlaneDiff (start, plane);
end_dist = PlaneDiff (end, plane);
offset = calc_offset (trace, plane);
if (start_dist >= offset && end_dist >= offset) {
// entirely in front of the plane
plane = 0;
if (hull->nodeleafs)
leaf = hull->nodeleafs[num].leafs[0];
num = node->children[0];
continue;
}
//non-zero offset lets the object touch the plane but still be
//behind the plane. however, point traces are assumed to be on the
//front side of the plane if touching the plane
if ((offset && start_dist <= -offset && end_dist <= -offset)
|| (!offset && start_dist < -offset && end_dist < -offset)) {
// entirely behind the plane
plane = 0;
if (hull->nodeleafs)
leaf = hull->nodeleafs[num].leafs[1];
num = node->children[1];
continue;
}
// cross the plane
if (start_dist == end_dist) {
// avoid division by zero (non-point clip only)
// since neither side is forward and we need to check both sides
// anyway, it doesn't matter which side we start with, so long as
// the fractions are correct.
side = 0;
frac[0] = 1;
frac[1] = 0;
} else {
// choose the side such that we are always moving forward through
// the map
side = start_dist < end_dist;
// if either start or end have the box straddling the plane, then
// frac will be appropriately clipped to 0 and 1, otherwise, frac
// will be inside that range
frac[0] = (start_dist + offset) / (start_dist - end_dist);
frac[1] = (start_dist - offset) / (start_dist - end_dist);
frac[0] = bound (0, frac[0], 1);
frac[1] = bound (0, frac[1], 1);
}
VectorSubtract (end, start, dist);
tstack->num = num;
tstack->side = side;
tstack->plane = plane;
// if the move is parallel to the plane, then the plane is not a good
// split plane
if (start_dist == end_dist)
tstack->plane = trace_state.split_plane;
VectorCopy (end, tstack->end);
VectorMultAdd (start, frac[side ^ 1], dist, tstack->start);
tstack->start_frac = frac[side ^ 1];
tstack++;
VectorMultAdd (start, frac[side], dist, end);
if (hull->nodeleafs)
leaf = hull->nodeleafs[num].leafs[side];
num = node->children[side];
}
}
VISIBLE int
MOD_HullContents (hull_t *hull, int num, const vec3_t origin, trace_t *trace)
{
int prevnode = -1;
int side = 0;
clipleaf_t *leaf;
// follow origin down the bsp tree to find the "central" leaf
while (num >= 0) {
vec_t d;
mclipnode_t *node;
plane_t *plane;
node = hull->clipnodes + num;
plane = hull->planes + node->planenum;
d = PlaneDiff (origin, plane);
prevnode = num;
side = d < 0;
num = node->children[side];
}
if (trace)
trace->contents = 0;
if (!trace || trace->type == tr_point
|| prevnode == -1 || !hull->nodeleafs) {
return num;
}
// check the contents of the "central" and surrounding touched leafs
leaf = hull->nodeleafs[prevnode].leafs[side];
test_count++;
return trace_contents (hull, trace, leaf, origin);
}
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