/*
 * Portions of this file are copyright Rebirth contributors and licensed as
 * described in COPYING.txt.
 * Portions of this file are copyright Parallax Software and licensed
 * according to the Parallax license below.
 * See COPYING.txt for license details.

THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
SOFTWARE CORPORATION ("PARALLAX").  PARALLAX, IN DISTRIBUTING THE CODE TO
END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
IN USING, DISPLAYING,  AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
FREE PURPOSES.  IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES.  THE END-USER UNDERSTANDS
AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
*/

/*
 *
 * Interrogation functions for segment data structure.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "key.h"
#include "gr.h"
#include "inferno.h"
#include "segment.h"
#include "editor.h"
#include "editor/esegment.h"
#include "dxxerror.h"
#include "object.h"
#include "gameseg.h"
#include "render.h"
#include "game.h"
#include "wall.h"
#include "switch.h"
#include "fuelcen.h"
#include "cntrlcen.h"
#include "seguvs.h"
#include "gameseq.h"
#include "kdefs.h"

#include "medwall.h"
#include "hostage.h"

#include "compiler-range_for.h"
#include "d_range.h"
#include "d_enumerate.h"
#include "d_zip.h"
#include "segiter.h"

int	Do_duplicate_vertex_check = 0;		// Gets set to 1 in med_create_duplicate_vertex, means to check for duplicate vertices in compress_mine

//	Remap all vertices in polygons in a segment through translation table xlate_verts.
int ToggleBottom(void)
{
	Render_only_bottom = !Render_only_bottom;
	Update_flags = UF_WORLD_CHANGED;
	return 0;
}

// -------------------------------------------------------------------------------
//	Return number of times vertex vi appears in all segments.
//	This function can be used to determine whether a vertex is used exactly once in
//	all segments, in which case it can be freely moved because it is not connected
//	to any other segment.
static int med_vertex_count(int vi)
{
	int		count;

	count = 0;

	range_for (auto &s, Segments)
	{
		auto sp = &s;
		if (sp->segnum != segment_none)
			range_for (auto &v, s.verts)
				if (v == vi)
					count++;
	}

	return count;
}

// -------------------------------------------------------------------------------
int is_free_vertex(int vi)
{
	return med_vertex_count(vi) == 1;
}

// -------------------------------------------------------------------------------
//	Return true if one fixed point number is very close to another, else return false.
static int fnear(fix f1, fix f2)
{
	return (abs(f1 - f2) <= FIX_EPSILON);
}

// -------------------------------------------------------------------------------
static int vnear(const vms_vector &vp1, const vms_vector &vp2)
{
	return fnear(vp1.x, vp2.x) && fnear(vp1.y, vp2.y) && fnear(vp1.z, vp2.z);
}

// -------------------------------------------------------------------------------
//	Add the vertex *vp to the global list of vertices, return its index.
//	Search until a matching vertex is found (has nearly the same coordinates) or until Num_vertices
// vertices have been looked at without a match.  If no match, add a new vertex.
int med_add_vertex(const vertex &vp)
{
	int	count;					// number of used vertices found, for loops exits when count == Num_vertices

//	set_vertex_counts();

	const auto Num_vertices = LevelSharedVertexState.Num_vertices;
	Assert(Num_vertices < MAX_SEGMENT_VERTICES);

	count = 0;
	unsigned free_index = UINT32_MAX;
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	for (unsigned v = 0; v < MAX_SEGMENT_VERTICES && count < Num_vertices; ++v)
		if (Vertex_active[v]) {
			count++;
			if (vnear(vp, Vertices.vcptr(v))) {
				return v;
			}
		} else if (free_index == UINT32_MAX)
			free_index = v;					// we want free_index to be the first free slot to add a vertex

	if (free_index == UINT32_MAX)
		free_index = Num_vertices;

	while (Vertex_active[free_index] && (free_index < MAX_VERTICES))
		free_index++;

	Assert(free_index < MAX_VERTICES);

	*Vertices.vmptr(free_index) = vp;
	Vertex_active[free_index] = 1;

	++LevelSharedVertexState.Num_vertices;

	if (Vertices.get_count() - 1 < free_index)
		Vertices.set_count(free_index + 1);

	return free_index;
}

namespace dsx {

// ------------------------------------------------------------------------------------------
//	Returns the index of a free segment.
//	Scans the Segments array.
segnum_t get_free_segment_number(segment_array &Segments)
{
	for (segnum_t segnum=0; segnum<MAX_SEGMENTS; segnum++)
		if (Segments[segnum].segnum == segment_none) {
			++ LevelSharedSegmentState.Num_segments;
			if (segnum > Highest_segment_index)
				Segments.set_count(segnum + 1);
			return segnum;
		}

	Assert(0);

	return 0;
}

// -------------------------------------------------------------------------------
//	Create a new segment, duplicating exactly, including vertex ids and children, the passed segment.
segnum_t med_create_duplicate_segment(segment_array &Segments, const segment &sp)
{
	const auto segnum = get_free_segment_number(Segments);

	auto &nsp = *Segments.vmptr(segnum);
	nsp = sp;
	nsp.objects = object_none;

	return segnum;
}

}

// -------------------------------------------------------------------------------
//	Add the vertex *vp to the global list of vertices, return its index.
//	This is the same as med_add_vertex, except that it does not search for the presence of the vertex.
int med_create_duplicate_vertex(const vertex &vp)
{
	const auto Num_vertices = LevelSharedVertexState.Num_vertices;
	Assert(Num_vertices < MAX_SEGMENT_VERTICES);

	Do_duplicate_vertex_check = 1;

	unsigned free_index = Num_vertices;

	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	while (Vertex_active[free_index] && (free_index < MAX_VERTICES))
		free_index++;

	Assert(free_index < MAX_VERTICES);

	auto &Vertices = LevelSharedVertexState.get_vertices();
	*Vertices.vmptr(free_index) = vp;
	Vertex_active[free_index] = 1;

	++LevelSharedVertexState.Num_vertices;

	if (Vertices.get_count() - 1 < free_index)
		Vertices.set_count(free_index + 1);

	return free_index;
}


// -------------------------------------------------------------------------------
//	Set the vertex *vp at index vnum in the global list of vertices, return its index (just for compatibility).
int med_set_vertex(const unsigned vnum, const vertex &vp)
{
	auto &Vertices = LevelSharedVertexState.get_vertices();
	*Vertices.vmptr(vnum) = vp;

	// Just in case this vertex wasn't active, mark it as active.
	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	if (!Vertex_active[vnum]) {
		Vertex_active[vnum] = 1;
		++LevelSharedVertexState.Num_vertices;
		if ((vnum > Vertices.get_count() - 1) && (vnum < NEW_SEGMENT_VERTICES)) {
			Vertices.set_count(vnum + 1);
		}
	}

	return vnum;
}

namespace dsx {

// -------------------------------------------------------------------------------
void create_removable_wall(fvcvertptr &vcvertptr, const vmsegptridx_t sp, const unsigned sidenum, const unsigned tmap_num)
{
	create_walls_on_side(vcvertptr, sp, sidenum);

	sp->unique_segment::sides[sidenum].tmap_num = tmap_num;

	assign_default_uvs_to_side(sp, sidenum);
	assign_light_to_side(sp, sidenum);
}

#if 0

// ---------------------------------------------------------------------------------------------
//	Orthogonalize matrix smat, returning result in rmat.
//	Does not modify smat.
//	Uses Gram-Schmidt process.
//	See page 172 of Strang, Gilbert, Linear Algebra and its Applications
//	Matt -- This routine should be moved to the vector matrix library.
//	It IS legal for smat == rmat.
//	We should also have the functions:
//		mat_a = mat_b * scalar;				// we now have mat_a = mat_a * scalar;
//		mat_a = mat_b + mat_c * scalar;	// or maybe not, maybe this is not primitive
void make_orthogonal(vms_matrix *rmat,vms_matrix *smat)
{
	vms_matrix		tmat;
	vms_vector		tvec1,tvec2;
	float				dot;

	// Copy source matrix to work area.
	tmat = *smat;

	// Normalize the three rows of the matrix tmat.
	vm_vec_normalize(&tmat.xrow);
	vm_vec_normalize(&tmat.yrow);
	vm_vec_normalize(&tmat.zrow);

	//	Now, compute the first vector.
	// This is very easy -- just copy the (normalized) source vector.
	rmat->zrow = tmat.zrow;

	// Now, compute the second vector.
	// From page 172 of Strang, we use the equation:
	//		b' = b - [transpose(q1) * b] * q1
	//	where:	b  = the second row of tmat
	//				q1 = the first row of rmat
	//				b' = the second row of rmat

	// Compute: transpose(q1) * b
	dot = vm_vec_dot(&rmat->zrow,&tmat.yrow);

	// Compute: b - dot * q1
	rmat->yrow.x = tmat.yrow.x - fixmul(dot,rmat->zrow.x);
	rmat->yrow.y = tmat.yrow.y - fixmul(dot,rmat->zrow.y);
	rmat->yrow.z = tmat.yrow.z - fixmul(dot,rmat->zrow.z);

	// Now, compute the third vector.
	// From page 173 of Strang, we use the equation:
	//		c' = c - (q1*c)*q1 - (q2*c)*q2
	//	where:	c  = the third row of tmat
	//				q1 = the first row of rmat
	//				q2 = the second row of rmat
	//				c' = the third row of rmat

	// Compute: q1*c
	dot = vm_vec_dot(&rmat->zrow,&tmat.xrow);

	tvec1.x = fixmul(dot,rmat->zrow.x);
	tvec1.y = fixmul(dot,rmat->zrow.y);
	tvec1.z = fixmul(dot,rmat->zrow.z);

	// Compute: q2*c
	dot = vm_vec_dot(&rmat->yrow,&tmat.xrow);

	tvec2.x = fixmul(dot,rmat->yrow.x);
	tvec2.y = fixmul(dot,rmat->yrow.y);
	tvec2.z = fixmul(dot,rmat->yrow.z);

	vm_vec_sub(&rmat->xrow,vm_vec_sub(&rmat->xrow,&tmat.xrow,&tvec1),&tvec2);
}

#endif

// ------------------------------------------------------------------------------------------
// Given a segment, extract the rotation matrix which defines it.
// Do this by extracting the forward, right, up vectors and then making them orthogonal.
// In the process of making the vectors orthogonal, favor them in the order forward, up, right.
// This means that the forward vector will remain unchanged.
void med_extract_matrix_from_segment(const shared_segment &sp, vms_matrix &rotmat)
{
	vms_vector	forwardvec,upvec;

	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	extract_forward_vector_from_segment(vcvertptr, sp, forwardvec);
	extract_up_vector_from_segment(vcvertptr, sp, upvec);

	if (((forwardvec.x == 0) && (forwardvec.y == 0) && (forwardvec.z == 0)) || ((upvec.x == 0) && (upvec.y == 0) && (upvec.z == 0))) {
		rotmat = vmd_identity_matrix;
		return;
	}


	vm_vector_2_matrix(rotmat, forwardvec, &upvec, nullptr);

#if 0
	vms_matrix	rm;

	extract_forward_vector_from_segment(sp,&rm.zrow);
	extract_right_vector_from_segment(sp,&rm.xrow);
	extract_up_vector_from_segment(sp,&rm.yrow);

	vm_vec_normalize(&rm.xrow);
	vm_vec_normalize(&rm.yrow);
	vm_vec_normalize(&rm.zrow);

	make_orthogonal(rotmat,&rm);

	vm_vec_normalize(&rotmat->xrow);
	vm_vec_normalize(&rotmat->yrow);
	vm_vec_normalize(&rotmat->zrow);

// *rotmat = rm; // include this line (and remove the call to make_orthogonal) if you don't want the matrix orthogonalized
#endif
}

}

// ------------------------------------------------------------------------------------------
//	Given a rotation matrix *rotmat which describes the orientation of a segment
//	and a side destside, return the rotation matrix which describes the orientation for the side.
void update_matrix_based_on_side(vms_matrix &rotmat,int destside)
{
        vms_angvec      rotvec;

	switch (destside) {
		case WLEFT:
                        vm_angvec_make(&rotvec,0,0,-16384);
			rotmat = vm_matrix_x_matrix(rotmat, vm_angles_2_matrix(rotvec));
			break;

		case WTOP:
                        vm_angvec_make(&rotvec,-16384,0,0);
			rotmat = vm_matrix_x_matrix(rotmat, vm_angles_2_matrix(rotvec));
			break;

		case WRIGHT:
                        vm_angvec_make(&rotvec,0,0,16384);
			rotmat = vm_matrix_x_matrix(rotmat, vm_angles_2_matrix(rotvec));
			break;

		case WBOTTOM:
                        vm_angvec_make(&rotvec,+16384,-32768,0);        // bank was -32768, but I think that was an erroneous compensation
			rotmat = vm_matrix_x_matrix(rotmat, vm_angles_2_matrix(rotvec));
			break;

		case WFRONT:
                        vm_angvec_make(&rotvec,0,0,-32768);
			rotmat = vm_matrix_x_matrix(rotmat, vm_angles_2_matrix(rotvec));
			break;

		case WBACK:
			break;
	}
}

//	-------------------------------------------------------------------------------------
static void change_vertex_occurrences(int dest, int src)
{
	// Fix vertices in groups
	range_for (auto &g, partial_range(GroupList, num_groups))
		g.vertices.replace(src, dest);

	// now scan all segments, changing occurrences of src to dest
	range_for (const auto &&segp, vmsegptr)
	{
		if (segp->segnum != segment_none)
			range_for (auto &v, segp->verts)
				if (v == src)
					v = dest;
	}
}

// --------------------------------------------------------------------------------------------------
static void compress_vertices(void)
{
	const auto Num_vertices = LevelSharedVertexState.Num_vertices;
	auto &Vertices = LevelSharedVertexState.get_vertices();
	if (Vertices.get_count() == Num_vertices)
		return;

	unsigned vert = Vertices.get_count() - 1;	//MAX_SEGMENT_VERTICES-1;

	auto &vcvertptr = Vertices.vcptr;
	auto &vmvertptr = Vertices.vmptr;
	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	for (unsigned hole = 0; hole < vert; ++hole)
		if (!Vertex_active[hole]) {
			// found an unused vertex which is a hole if a used vertex follows (not necessarily immediately) it.
			for ( ; (vert>hole) && (!Vertex_active[vert]); vert--)
				;

			if (vert > hole) {

				// Ok, hole is the index of a hole, vert is the index of a vertex which follows it.
				// Copy vert into hole, update pointers to it.
				*vmvertptr(hole) = *vcvertptr(vert);
				change_vertex_occurrences(hole, vert);

				vert--;
			}
		}

	Vertices.set_count(Num_vertices);
}

// --------------------------------------------------------------------------------------------------
static void compress_segments(void)
{
	auto &Objects = LevelUniqueObjectState.Objects;
	auto &vmobjptridx = Objects.vmptridx;
	if (Highest_segment_index == LevelSharedSegmentState.Num_segments - 1)
		return;

	segnum_t		hole,seg;
	seg = Highest_segment_index;

	auto &RobotCenters = LevelSharedRobotcenterState.RobotCenters;
	auto &Walls = LevelUniqueWallSubsystemState.Walls;
	auto &vmwallptr = Walls.vmptr;
	for (hole=0; hole < seg; hole++)
		if (Segments[hole].segnum == segment_none) {
			// found an unused segment which is a hole if a used segment follows (not necessarily immediately) it.
			for ( ; (seg>hole) && (Segments[seg].segnum == segment_none); seg--)
				;

			if (seg > hole) {
				// Ok, hole is the index of a hole, seg is the index of a segment which follows it.
				// Copy seg into hole, update pointers to it, update Cursegp, Markedsegp if necessary.
				Segments[hole] = Segments[seg];
				Segments[seg].segnum = segment_none;

				if (Cursegp == &Segments[seg])
					Cursegp = imsegptridx(hole);

				if (Markedsegp == &Segments[seg])
					Markedsegp = imsegptridx(hole);

				// Fix segments in groups
				range_for (auto &g, partial_range(GroupList, num_groups))
					g.segments.replace(seg, hole);

				// Fix walls
				range_for (const auto &&w, vmwallptr)
					if (w->segnum == seg)
						w->segnum = hole;

				// Fix fuelcenters, robotcens, and triggers... added 2/1/95 -Yuan
				range_for (auto &f, partial_range(LevelUniqueFuelcenterState.Station, LevelUniqueFuelcenterState.Num_fuelcenters))
					if (f.segnum == seg)
						f.segnum = hole;

				range_for (auto &f, partial_range(RobotCenters, LevelSharedRobotcenterState.Num_robot_centers))
					if (f.segnum == seg)
						f.segnum = hole;

				auto &Triggers = LevelUniqueWallSubsystemState.Triggers;
				auto &vmtrgptr = Triggers.vmptr;
				range_for (const auto vt, vmtrgptr)
				{
					auto &t = *vt;
					range_for (auto &l, partial_range(t.seg, t.num_links))
						if (l == seg)
							l = hole;
				}

				auto &sp = *vmsegptr(hole);
				range_for (auto &s, sp.children)
				{
					if (IS_CHILD(s)) {
						// Find out on what side the segment connection to the former seg is on in *csegp.
						range_for (auto &t, vmsegptr(s)->children)
						{
							if (t == seg) {
								t = hole;					// It used to be connected to seg, so make it connected to hole
							}
						}	// end for t
					}	// end if
				}	// end for s

				//Update object segment pointers
				range_for (const auto objp, objects_in(sp, vmobjptridx, vmsegptr))
				{
					Assert(objp->segnum == seg);
					objp->segnum = hole;
				}

				seg--;

			}	// end if (seg > hole)
		}	// end if

	Segments.set_count(LevelSharedSegmentState.Num_segments);
	med_create_new_segment_from_cursegp();

}


// -------------------------------------------------------------------------------
//	Combine duplicate vertices.
//	If two vertices have the same coordinates, within some small tolerance, then assign
//	the same vertex number to the two vertices, freeing up one of the vertices.
void med_combine_duplicate_vertices(array<uint8_t, MAX_VERTICES> &vlp)
{
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptridx = Vertices.vcptridx;
	const auto &&range = make_range(vcvertptridx);
	// Note: ok to do to <, rather than <= because w for loop starts at v+1
	if (range.m_begin == range.m_end)
		return;
	for (auto i = range.m_begin;;)
	{
		const auto &&v = *i;
		if (++i == range.m_end)
			return;
		if (vlp[v]) {
			auto &vvp = *v;
			auto subrange = range;
			subrange.m_begin = i;
			range_for (auto &&w, subrange)
				if (vlp[w]) {	//	used to be Vertex_active[w]
					if (vnear(vvp, *w)) {
						change_vertex_occurrences(v, w);
					}
				}
		}
	}
}

// ------------------------------------------------------------------------------
//	Compress mine at Segments and Vertices by squeezing out all holes.
//	If no holes (ie, an unused segment followed by a used segment), then no action.
//	If Cursegp or Markedsegp is a segment which gets moved to fill in a hole, then
//	they are properly updated.
void med_compress_mine(void)
{
	if (Do_duplicate_vertex_check) {
		auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
		med_combine_duplicate_vertices(Vertex_active);
		Do_duplicate_vertex_check = 0;
	}

	compress_segments();
	compress_vertices();
	set_vertex_counts();

	//--repair-- create_local_segment_data();

	//	This is necessary becuase a segment search (due to click in 3d window) uses the previous frame's
	//	segment information, which could get changed by this.
	Update_flags = UF_WORLD_CHANGED;
}

namespace dsx {

// ------------------------------------------------------------------------------------------
//	Copy texture map ids for each face in sseg to dseg.
static void copy_tmap_ids(unique_segment &dseg, const unique_segment &sseg)
{
	range_for (const auto &&z, zip(sseg.sides, dseg.sides))
	{
		auto &ds = std::get<1>(z);
		ds.tmap_num = std::get<0>(z).tmap_num;
		ds.tmap_num2 = 0;
	}
}

// ------------------------------------------------------------------------------------------
//	Attach a segment with a rotated orientation.
// Return value:
//  0 = successful attach
//  1 = No room in Segments[].
//  2 = No room in Vertices[].
//  3 = newside != WFRONT -- for now, the new segment must be attached at its (own) front side
//	 4 = already a face attached on destseg:destside
static int med_attach_segment_rotated(const vmsegptridx_t destseg, const vmsegptr_t newseg, int destside, int newside,const vms_matrix &attmat)
{
	vms_matrix	rotmat,rotmat2,rotmat3;
	vms_vector	forvec,upvec;

	// Return if already a face attached on this side.
	if (IS_CHILD(destseg->children[destside]))
		return 4;

	const auto segnum = get_free_segment_number(Segments);

	forvec = attmat.fvec;
	upvec = attmat.uvec;

	//	We are pretty confident we can add the segment.
	const auto &&nsp = destseg.absolute_sibling(segnum);

	nsp->segnum = segnum;
	nsp->objects = object_none;
	nsp->matcen_num = -1;

	// Copy group value.
	nsp->group = destseg->group;

	// Add segment to proper group list.
	if (nsp->group > -1)
		add_segment_to_group(nsp, nsp->group);

	// Copy the texture map ids.
	copy_tmap_ids(nsp,newseg);

	// clear all connections
	for (unsigned side = 0; side < MAX_SIDES_PER_SEGMENT; ++side)
	{
		nsp->children[side] = segment_none;
		nsp->shared_segment::sides[side].wall_num = wall_none;	
	}

	// Form the connection
	destseg->children[destside] = segnum;
//	destseg->sides[destside].render_flag = 0;
	nsp->children[newside] = destseg;

	// Copy vertex indices of the four vertices forming the joint
	auto &dvp = Side_to_verts[destside];

	// Set the vertex indices for the four vertices forming the front of the new side
	range_for (const unsigned v, xrange(4u))
                nsp->verts[v] = destseg->verts[static_cast<int>(dvp[v])];

	// The other 4 vertices must be created.
	// Their coordinates are determined by the 4 welded vertices and the vector from front
	// to back of the original *newseg.

	// Do lots of hideous matrix stuff, about 3/4 of which could probably be simplified out.
	med_extract_matrix_from_segment(destseg, rotmat);		// get orientation matrix for destseg (orthogonal rotation matrix)
	update_matrix_based_on_side(rotmat,destside);
	const auto rotmat1 = vm_vector_2_matrix(forvec,&upvec,nullptr);
	const auto rotmat4 = vm_matrix_x_matrix(rotmat,rotmat1);			// this is the desired orientation of the new segment
	med_extract_matrix_from_segment(newseg, rotmat3);		// this is the current orientation of the new segment
	vm_transpose_matrix(rotmat3);								// get the inverse of the current orientation matrix
	vm_matrix_x_matrix(rotmat2,rotmat4,rotmat3);			// now rotmat2 takes the current segment to the desired orientation

	// Warning -- look at this line!
	vm_transpose_matrix(rotmat2);	// added 12:33 pm, 10/01/93

	// Compute and rotate the center point of the attaching face.
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	const auto &&vc0 = compute_center_point_on_side(vcvertptr, newseg, newside);
	const auto vr = vm_vec_rotate(vc0,rotmat2);

	// Now rotate the free vertices in the segment
	array<vertex, 4> tvs;
	range_for (const unsigned v, xrange(4u))
		vm_vec_rotate(tvs[v], vcvertptr(newseg->verts[v + 4]), rotmat2);

	// Now translate the new segment so that the center point of the attaching faces are the same.
	const auto &&vc1 = compute_center_point_on_side(vcvertptr, destseg, destside);
	const auto xlate_vec = vm_vec_sub(vc1,vr);

	// Create and add the 4 new vertices.
	range_for (const unsigned v, xrange(4u))
	{
		vm_vec_add2(tvs[v],xlate_vec);
		nsp->verts[v+4] = med_add_vertex(tvs[v]);
	}

	set_vertex_counts();

	// Now all the vertices are in place.  Create the faces.
	validate_segment(vcvertptr, nsp);

	//	Say to not render at the joint.
//	destseg->sides[destside].render_flag = 0;
//	nsp->sides[newside].render_flag = 0;

	Cursegp = nsp;

	return	0;
}


// ------------------------------------------------------------------------------------------
// Attach side newside of newseg to side destside of destseg.
// Copies *newseg into global array Segments, increments Num_segments.
// Forms a weld between the two segments by making the new segment fit to the old segment.
// Updates number of faces per side if necessitated by new vertex coordinates.
//	Updates Cursegp.
// Return value:
//  0 = successful attach
//  1 = No room in Segments[].
//  2 = No room in Vertices[].
//  3 = newside != WFRONT -- for now, the new segment must be attached at its (own) front side
//	 4 = already a face attached on side newside
int med_attach_segment(const vmsegptridx_t destseg, const vmsegptr_t newseg, int destside, int newside)
{
	int		rval;
	const auto ocursegp = Cursegp;

	vms_angvec	tang = {0,0,0};
	const auto &&rotmat = vm_angles_2_matrix(tang);
	rval = med_attach_segment_rotated(destseg,newseg,destside,newside,rotmat);
	med_propagate_tmaps_to_segments(ocursegp,Cursegp,0);
	med_propagate_tmaps_to_back_side(Cursegp, Side_opposite[newside],0);
	copy_uvs_seg_to_seg(vmsegptr(&New_segment), Cursegp);

	return rval;
}

}

// -------------------------------------------------------------------------------
//	Delete a vertex, sort of.
//	Decrement the vertex count.  If the count goes to 0, then the vertex is free (has been deleted).
static void delete_vertex(const unsigned v)
{
	Assert(v < MAX_VERTICES);			// abort if vertex is not in array Vertices
	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	Assert(Vertex_active[v] >= 1);	// abort if trying to delete a non-existent vertex

	Vertex_active[v]--;
}

// -------------------------------------------------------------------------------
//	Update Num_vertices.
//	This routine should be called by anyone who calls delete_vertex.  It could be called in delete_vertex,
//	but then it would be called much more often than necessary, and it is a slow routine.
static void update_num_vertices(void)
{
	// Now count the number of vertices.
	unsigned n = 0;
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	range_for (const auto v, partial_range(Vertex_active, Vertices.get_count()))
		if (v)
			++n;
	LevelSharedVertexState.Num_vertices = n;
}

namespace dsx {

// -------------------------------------------------------------------------------
//	Set Vertex_active to number of occurrences of each vertex.
//	Set Num_vertices.
void set_vertex_counts(void)
{
	unsigned Num_vertices = 0;

	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	Vertex_active = {};

	// Count number of occurrences of each vertex.
	range_for (const auto &&segp, vmsegptr)
	{
		if (segp->segnum != segment_none)
			range_for (auto &v, segp->verts)
			{
				if (!Vertex_active[v])
					Num_vertices++;
				++ Vertex_active[v];
			}
	}
	LevelSharedVertexState.Num_vertices = Num_vertices;
}

// -------------------------------------------------------------------------------
//	Delete all vertices in segment *sp from the vertex list if they are not contained in another segment.
//	This is kind of a dangerous routine.  It modifies the global array Vertex_active, using the field as
//	a count.
static void delete_vertices_in_segment(const shared_segment &sp)
{
//	init_vertices();
	set_vertex_counts();
	// Subtract one count for each appearance of vertex in deleted segment
	range_for (auto &v, sp.verts)
		delete_vertex(v);

	update_num_vertices();
}

// -------------------------------------------------------------------------------
//	Delete segment *sp in Segments array.
// Return value:
//		0	successfully deleted.
//		1	unable to delete.
int med_delete_segment(const vmsegptridx_t sp)
{
	auto &Objects = LevelUniqueObjectState.Objects;
	auto &vmobjptr = Objects.vmptr;
	auto &vmobjptridx = Objects.vmptridx;
	segnum_t segnum = sp;
	// Cannot delete segment if only segment.
	if (LevelSharedSegmentState.Num_segments == 1)
		return 1;

	// Don't try to delete if segment doesn't exist.
	if (sp->segnum == segment_none) {
		return 1;
	}

	// Delete its refueling center if it has one
	fuelcen_delete(sp);

	delete_vertices_in_segment(sp);

	-- LevelSharedSegmentState.Num_segments;

	// If deleted segment has walls on any side, wipe out the wall.
	for (unsigned side = 0; side < MAX_SIDES_PER_SEGMENT; ++side)
		if (sp->shared_segment::sides[side].wall_num != wall_none) 
			wall_remove_side(sp, side);

	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	// Find out what this segment was connected to and break those connections at the other end.
	range_for (auto &side, sp->children)
		if (IS_CHILD(side)) {
			const auto &&csp = sp.absolute_sibling(side);
			for (int s=0; s<MAX_SIDES_PER_SEGMENT; s++)
				if (csp->children[s] == segnum) {
					csp->children[s] = segment_none;				// this is the side of connection, break it
					validate_segment_side(vcvertptr, csp, s);					// we have converted a connection to a side so validate the segment
					med_propagate_tmaps_to_back_side(csp,s,0);
				}
			Cursegp = csp;
			med_create_new_segment_from_cursegp();
			copy_uvs_seg_to_seg(vmsegptr(&New_segment), Cursegp);
		}

	sp->segnum = segment_none;										// Mark segment as inactive.

	// If deleted segment = marked segment, then say there is no marked segment
	if (sp == Markedsegp)
		Markedsegp = segment_none;
	
	//	If deleted segment = a Group segment ptr, then wipe it out.
	range_for (auto &s, partial_range(Groupsegp, num_groups))
		if (s == sp)
			s = nullptr;

	// If deleted segment = group segment, wipe it off the group list.
	if (sp->group > -1) 
			delete_segment_from_group(sp, sp->group);

	// If we deleted something which was not connected to anything, must now select a new current segment.
	if (Cursegp == sp)
		for (segnum_t s=0; s<MAX_SEGMENTS; s++)
			if ((Segments[s].segnum != segment_none) && (s!=segnum) ) {
				Cursegp = imsegptridx(s);
				med_create_new_segment_from_cursegp();
		   	break;
			}

	// If deleted segment contains objects, wipe out all objects
		range_for (const auto objnum, objects_in(*sp, vmobjptridx, vmsegptr))
		{
			//if an object is in the seg, delete it
			//if the object is the player, move to new curseg
			if (objnum == ConsoleObject)	{
				compute_segment_center(vcvertptr, ConsoleObject->pos,Cursegp);
				obj_relink(vmobjptr, vmsegptr, objnum, Cursegp);
			} else
				obj_delete(LevelUniqueObjectState, Segments, objnum);
		}

	// Make sure everything deleted ok...
	Assert( sp->objects==object_none );

	// If we are leaving many holes in Segments or Vertices, then compress mine, because it is inefficient to be that way
//	if ((Highest_segment_index > Num_segments+4) || (Highest_vertex_index > Num_vertices+4*8))
//		med_compress_mine();

	return 0;
}

// ------------------------------------------------------------------------------------------
//	Copy texture maps from sseg to dseg
static void copy_tmaps_to_segment(segment &dstseg, const segment &srcseg)
{
	shared_segment &shared_dst_seg = dstseg;
	unique_segment &unique_dst_seg = dstseg;
	const shared_segment &shared_src_seg = srcseg;
	const unique_segment &unique_src_seg = srcseg;
	range_for (const auto &&z, zip(shared_src_seg.sides, shared_dst_seg.sides, unique_src_seg.sides, unique_dst_seg.sides))
	{
		auto &shared_src_side = std::get<0>(z);
		auto &shared_dst_side = std::get<1>(z);
		auto &unique_src_side = std::get<2>(z);
		auto &unique_dst_side = std::get<3>(z);
		shared_dst_side.set_type(shared_src_side.get_type());
		unique_dst_side.tmap_num = unique_src_side.tmap_num;
		unique_dst_side.tmap_num2 = unique_src_side.tmap_num2;
	}

}

// ------------------------------------------------------------------------------------------
// Rotate the segment *seg by the pitch, bank, heading defined by *rot, destructively
// modifying its four free vertices in the global array Vertices.
// It is illegal to rotate a segment which has connectivity != 1.
// Pitch, bank, heading are about the point which is the average of the four points
// forming the side of connection.
// Return value:
//  0 = successful rotation
//  1 = Connectivity makes rotation illegal (connected to 0 or 2+ segments)
//  2 = Rotation causes degeneracy, such as self-intersecting segment.
//	 3 = Unable to rotate because not connected to exactly 1 segment.
int med_rotate_segment(const vmsegptridx_t seg, const vms_matrix &rotmat)
{
	int             newside=0,destside;
	int		count;

	// Find side of attachment
	count = 0;
	range_for (const auto &&es, enumerate(seg->children))
		if (IS_CHILD(es.value))
		{
			count++;
			newside = es.idx;
		}

	// Return if passed in segment is connected to other than 1 segment.
	if (count != 1)
		return 3;

	const auto &&destseg = seg.absolute_sibling(seg->children[newside]);

	destside = 0;
	while (destside < MAX_SIDES_PER_SEGMENT && destseg->children[destside] != seg)
		destside++;
		
	// Before deleting the segment, copy its texture maps to New_segment
	copy_tmaps_to_segment(vmsegptr(&New_segment), seg);

	if (Curside == WFRONT)
		Curside = WBACK;

	med_attach_segment_rotated(destseg, vmsegptr(&New_segment), destside, AttachSide, rotmat);

	//	Save tmap_num on each side to restore after call to med_propagate_tmaps_to_segments and _back_side
	//	which will change the tmap nums.
	array<int16_t, MAX_SIDES_PER_SEGMENT> side_tmaps;
	range_for (const auto &&z, zip(side_tmaps, seg->unique_segment::sides))
	{
		const unique_side &us = std::get<1>(z);
		std::get<0>(z) = us.tmap_num;
	}

	auto back_side = Side_opposite[find_connect_side(destseg, seg)];

	med_propagate_tmaps_to_segments(destseg, seg,0);
	med_propagate_tmaps_to_back_side(seg, back_side,0);

	range_for (const auto &&ez, enumerate(zip(side_tmaps, seg->unique_segment::sides)))
		if (ez.idx != back_side)
		{
			unique_side &us = std::get<1>(ez.value);
			us.tmap_num = std::get<0>(ez.value);
		}

	return	0;
}

// @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

// ----------------------------------------------------------------------------
//	Compute the sum of the distances between the four pairs of points.
//	The connections are:
//		firstv1 : 0		(firstv1+1)%4 : 1		(firstv1+2)%4 : 2		(firstv1+3)%4 : 3
static fix seg_seg_vertex_distsum(const vcsegptr_t seg1, const unsigned side1, const vcsegptr_t seg2, const unsigned side2, const unsigned firstv1)
{
	fix	distsum;

	distsum = 0;
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	range_for (const unsigned secondv, xrange(4u))
	{
		const unsigned firstv = (4 - secondv + (3 - firstv1)) % 4;
		distsum += vm_vec_dist(vcvertptr(seg1->verts[Side_to_verts[side1][firstv]]),vcvertptr(seg2->verts[Side_to_verts[side2][secondv]]));
	}

	return distsum;

}

// ----------------------------------------------------------------------------
//	Determine how to connect two segments together with the least amount of twisting.
//	Returns vertex index in 0..3 on first segment.  Assumed ordering of vertices
//	on second segment is 0,1,2,3.
//	So, if return value is 2, connect 2:0 3:1 0:2 1:3.
//	Theory:
//		We select an ordering of vertices for connection.  For the first pair of vertices to be connected,
//		compute the vector.  For the three remaining pairs of vertices, compute the vectors from one vertex
//		to the other.  Compute the dot products of these vectors with the original vector.  Add them up.
//		The close we are to 3, the better fit we have.  Reason:  The largest value for the dot product is
//		1.0, and this occurs for a parallel set of vectors.
static int get_index_of_best_fit(const vcsegptr_t seg1, int side1, const vcsegptr_t seg2, int side2)
{
	int	firstv;
	fix	min_distance;
	int	best_index=0;

	min_distance = F1_0*30000;

	for (firstv=0; firstv<4; firstv++) {
		fix t;
		t = seg_seg_vertex_distsum(seg1, side1, seg2, side2, firstv);
		if (t <= min_distance) {
			min_distance = t;
			best_index = firstv;
		}
	}

	return best_index;

}


#define MAX_VALIDATIONS 50

// ----------------------------------------------------------------------------
//	Remap uv coordinates in all sides in segment *sp which have a vertex in vp[4].
//	vp contains absolute vertex indices.
static void remap_side_uvs(const vmsegptridx_t sp, const array<int, 4> &vp)
{
	range_for (const auto &&es, enumerate(Side_to_verts))
	{
		range_for (const auto v, es.value)
			range_for (auto &i, vp) // scan each vertex in vp[4]
				if (v == i) {
					assign_default_uvs_to_side(sp, es.idx);					// Side s needs to be remapped
					goto next_side;
				}
next_side: ;
	}
}

// ----------------------------------------------------------------------------
//	Modify seg2 to share side2 with seg1:side1.  This forms a connection between
//	two segments without creating a new segment.  It modifies seg2 by sharing
//	vertices from seg1.  seg1 is not modified.  Four vertices from seg2 are
//	deleted.
//	Return code:
//		0			joint formed
//		1			-- no, this is legal! -- unable to form joint because one or more vertices of side2 is not free
//		2			unable to form joint because side1 is already used
int med_form_joint(const vmsegptridx_t seg1, int side1, const vmsegptridx_t seg2, int side2)
{
	int		bfi,v,s1;
	array<int, 4> lost_vertices, remap_vertices;
	array<segnum_t, MAX_VALIDATIONS> validation_list;
	uint_fast32_t nv;

	//	Make sure that neither side is connected.
	if (IS_CHILD(seg1->children[side1]) || IS_CHILD(seg2->children[side2]))
		return 2;

	// Make sure there is no wall there 
	if ((seg1->shared_segment::sides[side1].wall_num != wall_none) || (seg2->shared_segment::sides[side2].wall_num != wall_none))
		return 2;

	//	We can form the joint.  Find the best orientation of vertices.
	bfi = get_index_of_best_fit(seg1, side1, seg2, side2);

	auto &vp1 = Side_to_verts[side1];
	auto &vp2 = Side_to_verts[side2];

	//	Make a copy of the list of vertices in seg2 which will be deleted and set the
	//	associated vertex number, so that all occurrences of the vertices can be replaced.
	for (v=0; v<4; v++)
                lost_vertices[v] = seg2->verts[static_cast<int>(vp2[v])];

	//	Now, for each vertex in lost_vertices, determine which vertex it maps to.
	for (v=0; v<4; v++)
                remap_vertices[3 - ((v + bfi) % 4)] = seg1->verts[static_cast<int>(vp1[v])];

	// Now, in all segments, replace all occurrences of vertices in lost_vertices with remap_vertices

	// Put the one segment we know are being modified into the validation list.
	// Note: seg1 does not require a full validation, only a validation of the affected side.  Its vertices do not move.
	nv = 1;
	validation_list[0] = seg2;

	for (v=0; v<4; v++)
		range_for (const auto &&segp, vmsegptridx)
		{
			if (segp->segnum != segment_none)
				range_for (auto &sv, segp->verts)
					if (sv == lost_vertices[v]) {
						sv = remap_vertices[v];
						// Add segment to list of segments to be validated.
						for (s1=0; s1<nv; s1++)
							if (validation_list[s1] == segp)
								break;
						if (s1 == nv)
							validation_list[nv++] = segp;
						Assert(nv < MAX_VALIDATIONS);
					}
		}

	//	Form new connections.
	seg1->children[side1] = seg2;
	seg2->children[side2] = seg1;

	// validate all segments
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	validate_segment_side(vcvertptr, seg1, side1);
	range_for (auto &s, partial_const_range(validation_list, nv))
	{
		const auto &&segp = seg1.absolute_sibling(s);
		validate_segment(vcvertptr, segp);
		remap_side_uvs(segp, remap_vertices);	// remap uv coordinates on sides which were reshaped (ie, have a vertex in lost_vertices)
		warn_if_concave_segment(segp);
	}

	set_vertex_counts();

	return 0;
}

// ----------------------------------------------------------------------------
//	Create a new segment and use it to form a bridge between two existing segments.
//	Specify two segment:side pairs.  If either segment:side is not open (ie, segment->children[side] != -1)
//	then it is not legal to form the brider.
//	Return:
//		0	bridge segment formed
//		1	unable to form bridge because one (or both) of the sides is not open.
//	Note that no new vertices are created by this process.
int med_form_bridge_segment(const vmsegptridx_t seg1, int side1, const vmsegptridx_t seg2, int side2)
{
	int			v,bfi;

	if (IS_CHILD(seg1->children[side1]) || IS_CHILD(seg2->children[side2]))
		return 1;

	const auto &&bs = seg1.absolute_sibling(get_free_segment_number(Segments));
	shared_segment &sbs = *bs;
	sbs.segnum = bs;
	bs->objects = object_none;

	// Copy vertices from seg2 into last 4 vertices of bridge segment.
	{
	auto &sv = Side_to_verts[side2];
	for (v=0; v<4; v++)
		sbs.verts[(3-v)+4] = seg2->verts[static_cast<int>(sv[v])];
	}

	// Copy vertices from seg1 into first 4 vertices of bridge segment.
	bfi = get_index_of_best_fit(seg1, side1, seg2, side2);

	{
	auto &sv = Side_to_verts[side1];
	for (v=0; v<4; v++)
                bs->verts[(v + bfi) % 4] = seg1->verts[static_cast<int>(sv[v])];
	}

	// Form connections to children, first initialize all to unconnected.
	range_for (const auto &&z, zip(sbs.children, sbs.sides))
	{
		std::get<0>(z) = segment_none;
		std::get<1>(z).wall_num = wall_none;
	}

	// Now form connections between segments.

	bs->children[AttachSide] = seg1;
	bs->children[Side_opposite[AttachSide]] = seg2;

	seg1->children[side1] = bs; //seg2 - Segments;
	seg2->children[side2] = bs; //seg1 - Segments;

	//	Validate bridge segment, and if degenerate, clean up mess.
	Degenerate_segment_found = 0;

	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	validate_segment(vcvertptr, bs);

	if (Degenerate_segment_found) {
		seg1->children[side1] = segment_none;
		seg2->children[side2] = segment_none;
		bs->children[AttachSide] = segment_none;
                bs->children[static_cast<int>(Side_opposite[AttachSide])] = segment_none;
		if (med_delete_segment(bs)) {
			Int3();
		}
		editor_status("Bridge segment would be degenerate, not created.\n");
		return 1;
	} else {
		validate_segment(vcvertptr, seg1);	// used to only validate side, but segment does more error checking: ,side1);
		validate_segment(vcvertptr, seg2);	// ,side2);
		med_propagate_tmaps_to_segments(seg1,bs,0);

		editor_status("Bridge segment formed.");
		warn_if_concave_segment(bs);
		return 0;
	}
}

// -------------------------------------------------------------------------------
//	Create a segment given center, dimensions, rotation matrix.
//	Note that the created segment will always have planar sides and rectangular cross sections.
//	It will be created with walls on all sides, ie not connected to anything.
void med_create_segment(const vmsegptridx_t sp,fix cx, fix cy, fix cz, fix length, fix width, fix height, const vms_matrix &mp)
{
	int			f;
	++ LevelSharedSegmentState.Num_segments;

	sp->segnum = 1;						// What to put here?  I don't know.

	// Form connections to children, of which it has none.
	for (unsigned i = 0; i < MAX_SIDES_PER_SEGMENT; ++i)
	{
		sp->children[i] = segment_none;
//		sp->sides[i].render_flag = 0;
		sp->shared_segment::sides[i].wall_num  = wall_none;
	}

	sp->group = -1;
	sp->matcen_num = -1;

	//	Create relative-to-center vertices, which are the rotated points on the box defined by length, width, height
	sp->verts[0] = med_add_vertex(vertex{vm_vec_rotate({+width/2, +height/2, -length/2}, mp)});
	sp->verts[1] = med_add_vertex(vertex{vm_vec_rotate({+width/2, -height/2, -length/2}, mp)});
	sp->verts[2] = med_add_vertex(vertex{vm_vec_rotate({-width/2, -height/2, -length/2}, mp)});
	sp->verts[3] = med_add_vertex(vertex{vm_vec_rotate({-width/2, +height/2, -length/2}, mp)});
	sp->verts[4] = med_add_vertex(vertex{vm_vec_rotate({+width/2, +height/2, +length/2}, mp)});
	sp->verts[5] = med_add_vertex(vertex{vm_vec_rotate({+width/2, -height/2, +length/2}, mp)});
	sp->verts[6] = med_add_vertex(vertex{vm_vec_rotate({-width/2, -height/2, +length/2}, mp)});
	sp->verts[7] = med_add_vertex(vertex{vm_vec_rotate({-width/2, +height/2, +length/2}, mp)});

	// Now create the vector which is the center of the segment and add that to all vertices.
	const vms_vector cv{cx, cy, cz};

	//	Now, add the center to all vertices, placing the segment in 3 space.
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vmvertptr = Vertices.vmptr;
	range_for (auto &i, sp->verts)
		vm_vec_add2(vmvertptr(i), cv);

	//	Set scale vector.
//	sp->scale.x = width;
//	sp->scale.y = height;
//	sp->scale.z = length;

	//	Add faces to all sides.
	auto &vcvertptr = Vertices.vcptr;
	for (f=0; f<MAX_SIDES_PER_SEGMENT; f++)
		create_walls_on_side(vcvertptr, sp, f);

	sp->objects = object_none;		//no objects in this segment

	// Assume nothing special about this segment
	sp->special = 0;
	sp->station_idx = station_none;
	sp->static_light = 0;
	sp->matcen_num = -1;

	copy_tmaps_to_segment(sp, vcsegptr(&New_segment));

	assign_default_uvs_to_segment(sp);
}

// ----------------------------------------------------------------------------------------------
//	Create New_segment using a specified scale factor.
void med_create_new_segment(const vms_vector &scale)
{
	int			t;
	const auto &&sp = vmsegptridx(&New_segment);
	fix			length,width,height;

	length = scale.z;
	width = scale.x;
	height = scale.y;

	sp->segnum = 1;						// What to put here?  I don't know.

	//	Create relative-to-center vertices, which are the points on the box defined by length, width, height
	t = LevelSharedVertexState.Num_vertices;
	sp->verts[0] = med_set_vertex(NEW_SEGMENT_VERTICES+0,{+width/2,+height/2,-length/2});
	sp->verts[1] = med_set_vertex(NEW_SEGMENT_VERTICES+1,{+width/2,-height/2,-length/2});
	sp->verts[2] = med_set_vertex(NEW_SEGMENT_VERTICES+2,{-width/2,-height/2,-length/2});
	sp->verts[3] = med_set_vertex(NEW_SEGMENT_VERTICES+3,{-width/2,+height/2,-length/2});
	sp->verts[4] = med_set_vertex(NEW_SEGMENT_VERTICES+4,{+width/2,+height/2,+length/2});
	sp->verts[5] = med_set_vertex(NEW_SEGMENT_VERTICES+5,{+width/2,-height/2,+length/2});
	sp->verts[6] = med_set_vertex(NEW_SEGMENT_VERTICES+6,{-width/2,-height/2,+length/2});
	sp->verts[7] = med_set_vertex(NEW_SEGMENT_VERTICES+7,{-width/2,+height/2,+length/2});
	LevelSharedVertexState.Num_vertices = t;

//	sp->scale = *scale;

	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	// Form connections to children, of which it has none, init faces and tmaps.
	range_for (const auto &&ez, enumerate(zip(sp->children, sp->shared_segment::sides, sp->unique_segment::sides)))
	{
		const auto s = ez.idx;
		std::get<0>(ez.value) = segment_none;
		shared_side &ss = std::get<1>(ez.value);
		unique_side &us = std::get<2>(ez.value);
		ss.wall_num = wall_none;
		create_walls_on_side(vcvertptr, sp, s);
		us.tmap_num = s + 1;					// assign some stupid old tmap to this side.
		us.tmap_num2 = 0;
	}

	Seg_orientation = {};

	sp->objects = object_none;		//no objects in this segment

	assign_default_uvs_to_segment(sp);

	// Assume nothing special about this segment
	sp->special = 0;
	sp->station_idx = station_none;
	sp->static_light = 0;
	sp->matcen_num = -1;
}

// -------------------------------------------------------------------------------
void med_create_new_segment_from_cursegp(void)
{
	vms_vector	scalevec;
	vms_vector	uvec, rvec, fvec;

	med_extract_up_vector_from_segment_side(Cursegp, Curside, uvec);
	med_extract_right_vector_from_segment_side(Cursegp, Curside, rvec);
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	extract_forward_vector_from_segment(vcvertptr, Cursegp, fvec);

	scalevec.x = vm_vec_mag(rvec);
	scalevec.y = vm_vec_mag(uvec);
	scalevec.z = vm_vec_mag(fvec);
	med_create_new_segment(scalevec);
}

// -------------------------------------------------------------------------------
//	Initialize all vertices to inactive status.
void init_all_vertices(void)
{
	auto &Vertex_active = LevelSharedVertexState.get_vertex_active();
	Vertex_active = {};
	range_for (auto &s, Segments)
		s.segnum = segment_none;
}

// -----------------------------------------------------------------------------
//	Create coordinate axes in orientation of specified segment, stores vertices at *vp.
void create_coordinate_axes_from_segment(const vmsegptr_t sp, array<unsigned, 16> &vertnums)
{
	vms_matrix	rotmat;
	vms_vector t;

	med_extract_matrix_from_segment(sp, rotmat);

	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	auto &vmvertptr = Vertices.vmptr;
	const auto &&v0 = vmvertptr(vertnums[0]);
	compute_segment_center(vcvertptr, v0, sp);

	t = rotmat.rvec;
	vm_vec_scale(t,i2f(32));
	vm_vec_add(vmvertptr(vertnums[1]), v0, t);

	t = rotmat.uvec;
	vm_vec_scale(t,i2f(32));
	vm_vec_add(vmvertptr(vertnums[2]), v0, t);

	t = rotmat.fvec;
	vm_vec_scale(t,i2f(32));
	vm_vec_add(vmvertptr(vertnums[3]), v0, t);
}

// -----------------------------------------------------------------------------
//	Determine if a segment is concave. Returns true if concave
static int check_seg_concavity(const vcsegptr_t s)
{
	vms_vector n0;
	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	range_for (auto &sn, Side_to_verts)
		for (unsigned vn = 0; vn <= 4; ++vn)
		{
			const auto n1 = vm_vec_normal(
				vcvertptr(s->verts[sn[vn % 4]]),
				vcvertptr(s->verts[sn[(vn + 1) % 4]]),
				vcvertptr(s->verts[sn[(vn + 2) % 4]]));

			//vm_vec_normalize(&n1);

			if (vn>0) if (vm_vec_dot(n0,n1) < f0_5) return 1;

			n0 = n1;
		}

	return 0;
}


// -----------------------------------------------------------------------------
//	Find all concave segments and add to list
void find_concave_segs()
{
	Warning_segs.clear();

	range_for (const auto &&s, vcsegptridx)
		if (s->segnum != segment_none)
			if (check_seg_concavity(s))
				Warning_segs.emplace_back(s);
}


// -----------------------------------------------------------------------------
void warn_if_concave_segments(void)
{
	find_concave_segs();

	if (!Warning_segs.empty())
	{
		editor_status_fmt("*** WARNING *** %d concave segments in mine! *** WARNING ***", Warning_segs.size());
    }
}

// -----------------------------------------------------------------------------
//	Check segment s, if concave, warn
void warn_if_concave_segment(const vmsegptridx_t s)
{
	int	result;

	result = check_seg_concavity(s);

	if (result) {
		Warning_segs.emplace_back(s);

			editor_status("*** WARNING *** New segment is concave! *** WARNING ***");
	} //else
        //editor_status("");
}


// -------------------------------------------------------------------------------
//	Find segment adjacent to sp:side.
//	Adjacent means a segment which shares all four vertices.
//	Return true if segment found and fill in segment in adj_sp and side in adj_side.
//	Return false if unable to find, in which case adj_sp and adj_side are undefined.
int med_find_adjacent_segment_side(const vmsegptridx_t sp, int side, imsegptridx_t &adj_sp, int *adj_side)
{
	array<int, 4> abs_verts;

	//	Stuff abs_verts[4] array with absolute vertex indices
	range_for (const unsigned v, xrange(4u))
		abs_verts[v] = sp->verts[Side_to_verts[side][v]];

	//	Scan all segments, looking for a segment which contains the four abs_verts
	range_for (const auto &&segp, vmsegptridx)
	{
		if (segp != sp)
		{
			range_for (auto &v, abs_verts)
			{												// do for each vertex in abs_verts
				range_for (auto &vv, segp->verts) // do for each vertex in segment
					if (v == vv)
						goto fass_found1;											// Current vertex (indexed by v) is present in segment, try next
				goto fass_next_seg;												// This segment doesn't contain the vertex indexed by v
			fass_found1: ;
			}		// end for v

			//	All four vertices in sp:side are present in segment seg.
			//	Determine side and return
			range_for (const auto &&es, enumerate(Side_to_verts))
			{
				range_for (const auto v, es.value)
				{
					range_for (auto &vv, abs_verts)
					{
						if (segp->verts[v] == vv)
							goto fass_found2;
					}
					goto fass_next_side;											// Couldn't find vertex v in current side, so try next side.
				fass_found2: ;
				}
				// Found all four vertices in current side.  We are done!
				adj_sp = segp;
				*adj_side = es.idx;
				return 1;
			fass_next_side: ;
			}
			Assert(0);	// Impossible -- we identified this segment as containing all 4 vertices of side "side", but we couldn't find them.
			return 0;
		fass_next_seg: ;
		}
	}

	return 0;
}


#define JOINT_THRESHOLD	10000*F1_0 		// (Huge threshold)

// -------------------------------------------------------------------------------
//	Find segment closest to sp:side.
//	Return true if segment found and fill in segment in adj_sp and side in adj_side.
//	Return false if unable to find, in which case adj_sp and adj_side are undefined.
int med_find_closest_threshold_segment_side(const vmsegptridx_t sp, int side, imsegptridx_t &adj_sp, int *adj_side, fix threshold)
{
	fix			current_dist, closest_seg_dist;

	if (IS_CHILD(sp->children[side]))
		return 0;

	auto &Vertices = LevelSharedVertexState.get_vertices();
	auto &vcvertptr = Vertices.vcptr;
	const auto &&vsc = compute_center_point_on_side(vcvertptr, sp, side);

	closest_seg_dist = JOINT_THRESHOLD;

	//	Scan all segments, looking for a segment which contains the four abs_verts
	range_for (const auto &&segp, vmsegptridx)
	{
		if (segp != sp) 
			range_for (const auto &&es, enumerate(segp->children))
			{
				if (!IS_CHILD(es.value))
				{
					const auto &&vtc = compute_center_point_on_side(vcvertptr, segp, es.idx);
					current_dist = vm_vec_dist( vsc, vtc );
					if (current_dist < closest_seg_dist) {
						adj_sp = segp;
						*adj_side = es.idx;
						closest_seg_dist = current_dist;
					}
				}
			}	
	}

	if (closest_seg_dist < threshold)
		return 1;
	else
		return 0;
}

}