/*
 * 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 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
*/

/*
 *
 * Rendering Stuff
 *
 */

#include <algorithm>
#include <bitset>
#include <limits>
#include <cstdlib>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include "render_state.h"
#include "inferno.h"
#include "segment.h"
#include "dxxerror.h"
#include "bm.h"
#include "texmap.h"
#include "render.h"
#include "game.h"
#include "object.h"
#include "laser.h"
#include "textures.h"
#include "screens.h"
#include "segpoint.h"
#include "wall.h"
#include "texmerge.h"
#include "physics.h"
#include "3d.h"
#include "gameseg.h"
#include "vclip.h"
#include "lighting.h"
#include "cntrlcen.h"
#include "newdemo.h"
#include "automap.h"
#include "endlevel.h"
#include "key.h"
#include "newmenu.h"
#include "u_mem.h"
#include "piggy.h"
#include "timer.h"
#include "effects.h"
#include "playsave.h"
#ifdef OGL
#include "ogl_init.h"
#endif
#include "args.h"

#include "compiler-integer_sequence.h"
#include "compiler-range_for.h"
#include "partial_range.h"
#include "segiter.h"

#ifdef EDITOR
#include "editor/editor.h"
#include "editor/esegment.h"
#endif

using std::min;
using std::max;

// (former) "detail level" values
#ifdef OGL
int Render_depth = MAX_RENDER_SEGS; //how many segments deep to render
#else
int Render_depth = 20; //how many segments deep to render
unsigned Max_linear_depth = 50; // Deepest segment at which linear interpolation will be used.
#endif

//used for checking if points have been rotated
int	Clear_window_color=-1;
int	Clear_window=2;	// 1 = Clear whole background window, 2 = clear view portals into rest of world, 0 = no clear

static uint16_t s_current_generation;

// When any render function needs to know what's looking at it, it should 
// access Viewer members.
object * Viewer = NULL;

vms_vector Viewer_eye;  //valid during render

fix Render_zoom = 0x9000;					//the player's zoom factor

#ifndef NDEBUG
static std::bitset<MAX_OBJECTS> object_rendered;
#endif

#ifdef EDITOR
int	Render_only_bottom=0;
int	Bottom_bitmap_num = 9;
#endif

//Global vars for window clip test
int Window_clip_left,Window_clip_top,Window_clip_right,Window_clip_bot;

#ifdef EDITOR
int _search_mode = 0;			//true if looking for curseg,side,face
short _search_x,_search_y;	//pixel we're looking at
static int found_side,found_face,found_poly;
static segnum_t found_seg;
static objnum_t found_obj;
#else
static const int _search_mode = 0;
#endif

#ifdef NDEBUG		//if no debug code, set these vars to constants

#ifdef EDITOR
const int Show_only_curside = 0;
#endif

#else

int Outline_mode=0,Show_only_curside=0;

int toggle_outline_mode(void)
{
	return Outline_mode = !Outline_mode;
}

int toggle_show_only_curside(void)
{
	return Show_only_curside = !Show_only_curside;
}
#endif

#ifndef NDEBUG
static void draw_outline(int nverts,cg3s_point *const *const pointlist)
{
	int i;

	gr_setcolor(BM_XRGB(63,63,63));

	for (i=0;i<nverts-1;i++)
		g3_draw_line(*pointlist[i],*pointlist[i+1]);

	g3_draw_line(*pointlist[i],*pointlist[0]);

}
#endif

fix flash_scale;

#define FLASH_CYCLE_RATE f1_0

static const fix Flash_rate = FLASH_CYCLE_RATE;

//cycle the flashing light for when mine destroyed
void flash_frame()
{
	static fixang flash_ang=0;

	if (!Control_center_destroyed && !Seismic_tremor_magnitude)
		return;

	if (Endlevel_sequence)
		return;

	if (PaletteBlueAdd > 10 )		//whiting out
		return;

//	flash_ang += fixmul(FLASH_CYCLE_RATE,FrameTime);
#if defined(DXX_BUILD_DESCENT_II)
	if (Seismic_tremor_magnitude) {
		fix	added_flash;

		added_flash = abs(Seismic_tremor_magnitude);
		if (added_flash < F1_0)
			added_flash *= 16;

		flash_ang += fixmul(Flash_rate, fixmul(FrameTime, added_flash+F1_0));
		flash_scale = fix_fastsin(flash_ang);
		flash_scale = (flash_scale + F1_0*3)/4;	//	gets in range 0.5 to 1.0
	} else
#endif
	{
		flash_ang += fixmul(Flash_rate,FrameTime);
		flash_scale = fix_fastsin(flash_ang);
		flash_scale = (flash_scale + f1_0)/2;
#if defined(DXX_BUILD_DESCENT_II)
		if (Difficulty_level == 0)
			flash_scale = (flash_scale+F1_0*3)/4;
#endif
	}


}

static inline int is_alphablend_eclip(int eclip_num)
{
#if defined(DXX_BUILD_DESCENT_II)
	if (eclip_num == ECLIP_NUM_FORCE_FIELD)
		return 1;
#endif
	return eclip_num == ECLIP_NUM_FUELCEN;
}

// ----------------------------------------------------------------------------
//	Render a face.
//	It would be nice to not have to pass in segnum and sidenum, but
//	they are used for our hideously hacked in headlight system.
//	vp is a pointer to vertex ids.
//	tmap1, tmap2 are texture map ids.  tmap2 is the pasty one.
static void render_face(segnum_t segnum, int sidenum, unsigned nv, const array<int, 4> &vp, int tmap1, int tmap2, array<g3s_uvl, 4> uvl_copy, WALL_IS_DOORWAY_result_t wid_flags)
{
	grs_bitmap  *bm;
#ifdef OGL
	grs_bitmap  *bm2 = NULL;
#endif

	array<g3s_lrgb, 4>		dyn_light;
	array<cg3s_point *, 4> pointlist;

	Assert(nv <= pointlist.size());

	for (uint_fast32_t i = 0; i < nv; i++) {
		dyn_light[i].r = dyn_light[i].g = dyn_light[i].b = uvl_copy[i].l;
		pointlist[i] = &Segment_points[vp[i]];
	}

#if defined(DXX_BUILD_DESCENT_I)
	(void)wid_flags;
#elif defined(DXX_BUILD_DESCENT_II)
	//handle cloaked walls
	if (wid_flags & WID_CLOAKED_FLAG) {
		auto wall_num = Segments[segnum].sides[sidenum].wall_num;
		Assert(wall_num != wall_none);
		gr_settransblend(Walls[wall_num].cloak_value, GR_BLEND_NORMAL);
		gr_setcolor(BM_XRGB(0, 0, 0));  // set to black (matters for s3)

		g3_draw_poly(nv, pointlist);    // draw as flat poly

		gr_settransblend(GR_FADE_OFF, GR_BLEND_NORMAL);

		return;
	}
#endif

	if (tmap1 >= NumTextures) {
#ifndef RELEASE
		Int3();
#endif
		Segments[segnum].sides[sidenum].tmap_num = 0;
	}

#ifdef OGL
	if (!GameArg.DbgUseOldTextureMerge){
		PIGGY_PAGE_IN(Textures[tmap1]);
		bm = &GameBitmaps[Textures[tmap1].index];
		if (tmap2){
			PIGGY_PAGE_IN(Textures[tmap2&0x3FFF]);
			bm2 = &GameBitmaps[Textures[tmap2&0x3FFF].index];
		}
		if (bm2 && (bm2->bm_flags&BM_FLAG_SUPER_TRANSPARENT)){
			bm = &texmerge_get_cached_bitmap( tmap1, tmap2 );
			bm2 = NULL;
		}
	}else
#endif

		// New code for overlapping textures...
		if (tmap2 != 0) {
			bm = &texmerge_get_cached_bitmap( tmap1, tmap2 );
		} else {
			bm = &GameBitmaps[Textures[tmap1].index];
			PIGGY_PAGE_IN(Textures[tmap1]);
		}

	Assert( !(bm->bm_flags & BM_FLAG_PAGED_OUT) );

	//set light values for each vertex & build pointlist
	for (uint_fast32_t i = 0;i < nv;i++)
	{
		//the uvl struct has static light already in it

		//scale static light for destruction effect
		if (Control_center_destroyed || Seismic_tremor_magnitude)	//make lights flash
			uvl_copy[i].l = fixmul(flash_scale,uvl_copy[i].l);
		//add in dynamic light (from explosions, etc.)
		uvl_copy[i].l += (Dynamic_light[vp[i]].r+Dynamic_light[vp[i]].g+Dynamic_light[vp[i]].b)/3;
		//saturate at max value
		if (uvl_copy[i].l > MAX_LIGHT)
			uvl_copy[i].l = MAX_LIGHT;

		// And now the same for the ACTUAL (rgb) light we want to use

		//scale static light for destruction effect
		if (Seismic_tremor_magnitude)	//make lights flash
			dyn_light[i].r = dyn_light[i].g = dyn_light[i].b = fixmul(flash_scale,uvl_copy[i].l);
		else if (Control_center_destroyed)	//make lights flash
		{
			if (PlayerCfg.DynLightColor) // let the mine glow red a little
			{
				dyn_light[i].r = fixmul(flash_scale>=f0_5*1.5?flash_scale:f0_5*1.5,uvl_copy[i].l);
				dyn_light[i].g = dyn_light[i].b = fixmul(flash_scale,uvl_copy[i].l);
			}
			else
				dyn_light[i].r = dyn_light[i].g = dyn_light[i].b = fixmul(flash_scale,uvl_copy[i].l);
		}

		// add light color
		dyn_light[i].r += Dynamic_light[vp[i]].r;
		dyn_light[i].g += Dynamic_light[vp[i]].g;
		dyn_light[i].b += Dynamic_light[vp[i]].b;
		// saturate at max value
		if (dyn_light[i].r > MAX_LIGHT)
			dyn_light[i].r = MAX_LIGHT;
		if (dyn_light[i].g > MAX_LIGHT)
			dyn_light[i].g = MAX_LIGHT;
		if (dyn_light[i].b > MAX_LIGHT)
			dyn_light[i].b = MAX_LIGHT;
		if (PlayerCfg.AlphaEffects) // due to additive blending, transparent sprites will become invivible in font of white surfaces (lamps). Fix that with a little desaturation
		{
			dyn_light[i].r *= .93;
			dyn_light[i].g *= .93;
			dyn_light[i].b *= .93;
		}
	}

	bool alpha = false;
	if (PlayerCfg.AlphaBlendEClips && is_alphablend_eclip(TmapInfo[tmap1].eclip_num)) // set nice transparency/blending for some special effects (if we do more, we should maybe use switch here)
	{
		alpha = true;
		gr_settransblend(GR_FADE_OFF, GR_BLEND_ADDITIVE_C);
	}

#ifdef EDITOR
	if ((Render_only_bottom) && (sidenum == WBOTTOM))
		g3_draw_tmap(nv,pointlist,uvl_copy,dyn_light,GameBitmaps[Textures[Bottom_bitmap_num].index]);
	else
#endif

#ifdef OGL
		if (bm2){
			g3_draw_tmap_2(nv,pointlist,uvl_copy,dyn_light,bm,bm2,((tmap2&0xC000)>>14) & 3);
		}else
#endif
			g3_draw_tmap(nv,pointlist,uvl_copy,dyn_light,*bm);

	if (alpha)
	gr_settransblend(GR_FADE_OFF, GR_BLEND_NORMAL); // revert any transparency/blending setting back to normal

#ifndef NDEBUG
	if (Outline_mode) draw_outline(nv, &pointlist[0]);
#endif
}

// ----------------------------------------------------------------------------
//	Only called if editor active.
//	Used to determine which face was clicked on.
static void check_face(segnum_t segnum, int sidenum, int facenum, unsigned nv, const array<int, 4> &vp, int tmap1, int tmap2, const array<g3s_uvl, 4> &uvl_copy)
{
#ifdef EDITOR
	if (_search_mode) {
		int save_lighting;
		array<g3s_lrgb, 4> dyn_light{};
		array<cg3s_point *, 4> pointlist;
#ifdef OGL
		(void)tmap1;
		(void)tmap2;
#else
		grs_bitmap *bm;
		if (tmap2 > 0 )
			bm = &texmerge_get_cached_bitmap( tmap1, tmap2 );
		else
			bm = &GameBitmaps[Textures[tmap1].index];
#endif
		for (uint_fast32_t i = 0; i < nv; i++) {
			dyn_light[i].r = dyn_light[i].g = dyn_light[i].b = uvl_copy[i].l;
			pointlist[i] = &Segment_points[vp[i]];
		}

		gr_setcolor(0);
#ifdef OGL
		ogl_end_frame();
#endif
		gr_pixel(_search_x,_search_y);	//set our search pixel to color zero
#ifdef OGL
		ogl_start_frame();
#endif
		gr_setcolor(1);					//and render in color one
		save_lighting = Lighting_on;
		Lighting_on = 2;
#ifdef OGL
		g3_draw_poly(nv,pointlist);
#else
		g3_draw_tmap(nv,pointlist, uvl_copy, dyn_light, *bm);
#endif
		Lighting_on = save_lighting;

		if (gr_ugpixel(grd_curcanv->cv_bitmap,_search_x,_search_y) == 1) {
			found_seg = segnum;
			found_obj = object_none;
			found_side = sidenum;
			found_face = facenum;
		}
	}
#else
	(void)segnum;
	(void)sidenum;
	(void)facenum;
	(void)nv;
	(void)vp;
	(void)tmap1;
	(void)tmap2;
	(void)uvl_copy;
#endif
}

template <std::size_t... N>
static inline void check_render_face(index_sequence<N...>, segnum_t segnum, int sidenum, unsigned facenum, const array<int, 4> &ovp, int tmap1, int tmap2, const array<uvl, 4> &uvlp, WALL_IS_DOORWAY_result_t wid_flags, const std::size_t nv)
{
	const array<int, 4> vp{{ovp[N]...}};
	const array<g3s_uvl, 4> uvl_copy{{
		{uvlp[N].u, uvlp[N].v, uvlp[N].l}...
	}};
	render_face(segnum, sidenum, nv, vp, tmap1, tmap2, uvl_copy, wid_flags);
	check_face(segnum, sidenum, facenum, nv, vp, tmap1, tmap2, uvl_copy);
}

template <std::size_t N0, std::size_t N1, std::size_t N2, std::size_t N3>
static inline void check_render_face(index_sequence<N0, N1, N2, N3> is, segnum_t segnum, int sidenum, unsigned facenum, const array<int, 4> &vp, int tmap1, int tmap2, const array<uvl, 4> &uvlp, WALL_IS_DOORWAY_result_t wid_flags)
{
	check_render_face(is, segnum, sidenum, facenum, vp, tmap1, tmap2, uvlp, wid_flags, 4);
}

/* Avoid default constructing final element of uvl_copy; if any members
 * are default constructed, gcc zero initializes all members.
 */
template <std::size_t N0, std::size_t N1, std::size_t N2>
static inline void check_render_face(index_sequence<N0, N1, N2>, segnum_t segnum, int sidenum, unsigned facenum, const array<int, 4> &vp, int tmap1, int tmap2, const array<uvl, 4> &uvlp, WALL_IS_DOORWAY_result_t wid_flags)
{
	check_render_face(index_sequence<N0, N1, N2, 3>(), segnum, sidenum, facenum, vp, tmap1, tmap2, uvlp, wid_flags, 3);
}

static const fix	Tulate_min_dot = (F1_0/4);
//--unused-- fix	Tulate_min_ratio = (2*F1_0);
static const fix	Min_n0_n1_dot	= (F1_0*15/16);

// -----------------------------------------------------------------------------------
//	Render a side.
//	Check for normal facing.  If so, render faces on side dictated by sidep->type.
static void render_side(const vcsegptridx_t segp, int sidenum)
{
	auto sidep = &segp->sides[sidenum];
	fix		min_dot, max_dot;
	vms_vector	normals[2];
	auto wid_flags = WALL_IS_DOORWAY(segp,sidenum);

	if (!(wid_flags & WID_RENDER_FLAG))		//if (WALL_IS_DOORWAY(segp, sidenum) == WID_NO_WALL)
		return;

	normals[0] = segp->sides[sidenum].normals[0];
	normals[1] = segp->sides[sidenum].normals[1];
	const auto vertnum_list = get_side_verts(segp,sidenum);

	//	Regardless of whether this side is comprised of a single quad, or two triangles, we need to know one normal, so
	//	deal with it, get the dot product.
	const unsigned which_vertnum =
#if defined(DXX_BUILD_DESCENT_II)
		/* Silly, but consistent with how it was at release */
		(sidep->get_type() == SIDE_IS_QUAD) ? 0 :
#endif
		(sidep->get_type() == SIDE_IS_TRI_13)
			? 1
			: 0;
	const auto tvec = vm_vec_normalized_quick(vm_vec_sub(Viewer_eye, Vertices[vertnum_list[which_vertnum]]));
	const auto v_dot_n0 = vm_vec_dot(tvec, normals[0]);
	//	========== Mark: Here is the change...beginning here: ==========

	index_sequence<0, 1, 2, 3> is_quad;
	if (sidep->get_type() == SIDE_IS_QUAD) {

		if (v_dot_n0 >= 0) {
			check_render_face(is_quad, segp, sidenum, 0, vertnum_list, sidep->tmap_num, sidep->tmap_num2, sidep->uvls, wid_flags);
		}
	} else {
		//	========== Mark: The change ends here. ==========

		//	Although this side has been triangulated, because it is not planar, see if it is acceptable
		//	to render it as a single quadrilateral.  This is a function of how far away the viewer is, how non-planar
		//	the face is, how normal to the surfaces the view is.
		//	Now, if both dot products are close to 1.0, then render two triangles as a single quad.
		const auto v_dot_n1 = vm_vec_dot(tvec, normals[1]);

		if (v_dot_n0 < v_dot_n1) {
			min_dot = v_dot_n0;
			max_dot = v_dot_n1;
		} else {
			min_dot = v_dot_n1;
			max_dot = v_dot_n0;
		}

		//	Determine whether to detriangulate side: (speed hack, assumes Tulate_min_ratio == F1_0*2, should fixmul(min_dot, Tulate_min_ratio))
		if (DETRIANGULATION && ((min_dot+F1_0/256 > max_dot) || ((Viewer->segnum != segp) &&  (min_dot > Tulate_min_dot) && (max_dot < min_dot*2)))) {
			fix	n0_dot_n1;

			//	The other detriangulation code doesn't deal well with badly non-planar sides.
			n0_dot_n1 = vm_vec_dot(normals[0], normals[1]);
			if (n0_dot_n1 < Min_n0_n1_dot)
				goto im_so_ashamed;

			check_render_face(is_quad, segp, sidenum, 0, vertnum_list, sidep->tmap_num, sidep->tmap_num2, sidep->uvls, wid_flags);
		} else {
im_so_ashamed: ;
			if (sidep->get_type() == SIDE_IS_TRI_02) {
				if (v_dot_n0 >= 0) {
					check_render_face(index_sequence<0, 1, 2>(), segp, sidenum, 0, vertnum_list, sidep->tmap_num, sidep->tmap_num2, sidep->uvls, wid_flags);
				}

				if (v_dot_n1 >= 0) {
					// want to render from vertices 0, 2, 3 on side
					check_render_face(index_sequence<0, 2, 3>(), segp, sidenum, 1, vertnum_list, sidep->tmap_num, sidep->tmap_num2, sidep->uvls, wid_flags);
				}
			} else if (sidep->get_type() ==  SIDE_IS_TRI_13) {
				if (v_dot_n1 >= 0) {
					// rendering 1,2,3, so just skip 0
					check_render_face(index_sequence<1, 2, 3>(), segp, sidenum, 1, vertnum_list, sidep->tmap_num, sidep->tmap_num2, sidep->uvls, wid_flags);
				}

				if (v_dot_n0 >= 0) {
					// want to render from vertices 0,1,3
					check_render_face(index_sequence<0, 1, 3>(), segp, sidenum, 0, vertnum_list, sidep->tmap_num, sidep->tmap_num2, sidep->uvls, wid_flags);
				}

			} else
				throw side::illegal_type(segp, sidep);
		}
	}

}

#ifdef EDITOR
static void render_object_search(const vobjptridx_t obj)
{
	int changed=0;

	//note that we draw each pixel object twice, since we cannot control
	//what color the object draws in, so we try color 0, then color 1,
	//in case the object itself is rendering color 0

	gr_setcolor(0);	//set our search pixel to color zero
#ifdef OGL
	ogl_end_frame();

	// For OpenGL we use gr_rect instead of gr_pixel,
	// because in some implementations (like my Macbook Pro 5,1)
	// point smoothing can't be turned off.
	// Point smoothing would change the pixel to dark grey, but it MUST be black.
	// Making a 3x3 rectangle wouldn't matter
	// (but it only seems to draw a single pixel anyway)
	gr_rect(_search_x - 1, _search_y - 1, _search_x + 1, _search_y + 1);

	ogl_start_frame();
#else
	gr_pixel(_search_x,_search_y);
#endif
	render_object(obj);
	if (gr_ugpixel(grd_curcanv->cv_bitmap,_search_x,_search_y) != 0)
		changed=1;

	gr_setcolor(1);
#ifdef OGL
	ogl_end_frame();
	gr_rect(_search_x - 1, _search_y - 1, _search_x + 1, _search_y + 1);
	ogl_start_frame();
#else
	gr_pixel(_search_x,_search_y);
#endif
	render_object(obj);
	if (gr_ugpixel(grd_curcanv->cv_bitmap,_search_x,_search_y) != 1)
		changed=1;

	if (changed) {
		if (obj->segnum != segment_none)
			Cursegp = segptridx(obj->segnum);
		found_seg = segment_none;
		found_obj = obj;
	}
}
#endif

static void do_render_object(const vobjptridx_t obj, window_rendered_data &window)
{
	#ifdef EDITOR
	int save_3d_outline=0;
	#endif
	int count = 0;

	#ifndef NDEBUG
	if (object_rendered[obj]) {		//already rendered this...
		Int3();		//get Matt!!!
		return;
	}

	object_rendered[obj] = true;
	#endif

#if defined(DXX_BUILD_DESCENT_II)
   if (Newdemo_state==ND_STATE_PLAYBACK)  
	 {
	  if ((DemoDoingLeft==6 || DemoDoingRight==6) && obj->type==OBJ_PLAYER)
		{
			// A nice fat hack: keeps the player ship from showing up in the
			// small extra view when guiding a missile in the big window
			
  			return; 
		}
	 }
#endif

	//	Added by MK on 09/07/94 (at about 5:28 pm, CDT, on a beautiful, sunny late summer day!) so
	//	that the guided missile system will know what objects to look at.
	//	I didn't know we had guided missiles before the release of D1. --MK
	if ((obj->type == OBJ_ROBOT) || (obj->type == OBJ_PLAYER)) {
		window.rendered_robots.emplace_back(obj);
	}

	if ((count++ > MAX_OBJECTS) || (obj->next == obj)) {
		Int3();					// infinite loop detected
		obj->next = object_none;		// won't this clean things up?
		return;					// get out of this infinite loop!
	}

		//g3_draw_object(obj->class_id,&obj->pos,&obj->orient,obj->size);

	//check for editor object

	#ifdef EDITOR
	if (EditorWindow && obj==Cur_object_index) {
		save_3d_outline = g3d_interp_outline;
		g3d_interp_outline=1;
	}
	#endif

	#ifdef EDITOR
	if (_search_mode)
		render_object_search(obj);
	else
	#endif
		//NOTE LINK TO ABOVE
		render_object(obj);

	for (objnum_t n=obj->attached_obj; n != object_none; n = Objects[n].ctype.expl_info.next_attach) {
		const auto o = vobjptridx(n);
		Assert(o->type == OBJ_FIREBALL);
		Assert(o->control_type == CT_EXPLOSION);
		Assert(o->flags & OF_ATTACHED);

		render_object(o);
	}


	#ifdef EDITOR
	if (EditorWindow && obj==Cur_object_index)
		g3d_interp_outline = save_3d_outline;
	#endif


}

//increment counter for checking if points rotated
//This must be called at the start of the frame if rotate_list() will be used
void render_start_frame()
{
	if (s_current_generation == std::numeric_limits<decltype(s_current_generation)>::max())
	{
		Segment_points = {};
		s_current_generation = 0;
	}
	++ s_current_generation;
}

//Given a lit of point numbers, rotate any that haven't been rotated this frame
g3s_codes rotate_list(std::size_t nv,const int *pointnumlist)
{
	g3s_codes cc;

	range_for (const auto pnum, unchecked_partial_range(pointnumlist, nv))
	{
		auto &pnt = Segment_points[pnum];
		if (pnt.p3_last_generation != s_current_generation)
		{
			pnt.p3_last_generation = s_current_generation;
			if (cheats.acid)
			{
				float f = (float) timer_query() / F1_0;
				vms_vector tmpv = Vertices[pnum];
				tmpv.x += fl2f(sinf(f * 2.0f + f2fl(tmpv.x)));
				tmpv.y += fl2f(sinf(f * 3.0f + f2fl(tmpv.y)));
				tmpv.z += fl2f(sinf(f * 5.0f + f2fl(tmpv.z)));
				g3_rotate_point(pnt,tmpv);
			}
			else
				g3_rotate_point(pnt,Vertices[pnum]);
		}
		cc.uand &= pnt.p3_codes;
		cc.uor  |= pnt.p3_codes;
	}

	return cc;

}

//Given a lit of point numbers, project any that haven't been projected
static void project_list(array<int, 8> &pointnumlist)
{
	range_for (const auto pnum, pointnumlist)
	{
		if (!(Segment_points[pnum].p3_flags & PF_PROJECTED))
			g3_project_point(Segment_points[pnum]);
	}
}


// -----------------------------------------------------------------------------------
#if !defined(OGL)
static void render_segment(const vcsegptridx_t seg)
{
	int			sn;

	g3s_codes 	cc=rotate_list(seg->verts);
	if (! cc.uand) {		//all off screen?

#if defined(DXX_BUILD_DESCENT_II)
      if (Viewer->type!=OBJ_ROBOT)
#endif
		Automap_visited[seg]=1;

		for (sn=0; sn<MAX_SIDES_PER_SEGMENT; sn++)
			render_side(seg, sn);
	}

	//draw any objects that happen to be in this segment

	//sort objects!
	//object_sort_segment_objects( seg );
}
#endif

// ----- This used to be called when Show_only_curside was set.
// ----- It is wholly and superiorly replaced by render_side.
// -- //render one side of one segment
// -- void render_seg_side(segment *seg,int _side)
// -- {
// -- 	g3s_codes cc;
// -- 	short vertnum_list[4];
// -- 
// -- 	cc=g3_rotate_list(8,&seg->verts);
// -- 
// -- 	if (! cc.uand) {		//all off screen?
// -- 		int fn,pn,i;
// -- 		side *s;
// -- 		face *f;
// -- 		poly *p;
// -- 
// -- 		s=&seg->sides[_side];
// -- 
// -- 		for (f=s->faces,fn=s->num_faces;fn;fn--,f++)
// -- 			for (p=f->polys,pn=f->num_polys;pn;pn--,p++) {
// -- 				grs_bitmap *tmap;
// -- 	
// -- 				for (i=0;i<p->num_vertices;i++) vertnum_list[i] = seg->verts[p->verts[i]];
// -- 	
// -- 				if (p->tmap_num >= NumTextures) {
// -- 					Warning("Invalid tmap number %d, NumTextures=%d\n...Changing in poly structure to tmap 0",p->tmap_num,NumTextures);
// -- 					p->tmap_num = 0;		//change it permanantly
// -- 				}
// -- 	
// -- 				tmap = Textures[p->tmap_num];
// -- 	
// -- 				g3_check_and_draw_tmap(p->num_vertices,vertnum_list,(g3s_uvl *) &p->uvls,tmap,&f->normal);
// -- 	
// -- 				if (Outline_mode) draw_outline(p->num_vertices,vertnum_list);
// -- 			}
// -- 		}
// -- 
// -- }

#ifdef EDITOR
#ifndef NDEBUG

const fix CROSS_WIDTH = i2f(8);
const fix CROSS_HEIGHT = i2f(8);

//draw outline for curside
static void outline_seg_side(const vcsegptr_t seg,int _side,int edge,int vert)
{
	g3s_codes cc=rotate_list(seg->verts);

	if (! cc.uand) {		//all off screen?
		g3s_point *pnt;

		//render curedge of curside of curseg in green

		gr_setcolor(BM_XRGB(0,63,0));
		g3_draw_line(Segment_points[seg->verts[Side_to_verts[_side][edge]]],Segment_points[seg->verts[Side_to_verts[_side][(edge+1)%4]]]);

		//draw a little cross at the current vert

		pnt = &Segment_points[seg->verts[Side_to_verts[_side][vert]]];

		g3_project_point(*pnt);		//make sure projected

//		gr_setcolor(BM_XRGB(0,0,63));
//		gr_line(pnt->p3_sx-CROSS_WIDTH,pnt->p3_sy,pnt->p3_sx+CROSS_WIDTH,pnt->p3_sy);
//		gr_line(pnt->p3_sx,pnt->p3_sy-CROSS_HEIGHT,pnt->p3_sx,pnt->p3_sy+CROSS_HEIGHT);

		gr_line(pnt->p3_sx-CROSS_WIDTH,pnt->p3_sy,pnt->p3_sx,pnt->p3_sy-CROSS_HEIGHT);
		gr_line(pnt->p3_sx,pnt->p3_sy-CROSS_HEIGHT,pnt->p3_sx+CROSS_WIDTH,pnt->p3_sy);
		gr_line(pnt->p3_sx+CROSS_WIDTH,pnt->p3_sy,pnt->p3_sx,pnt->p3_sy+CROSS_HEIGHT);
		gr_line(pnt->p3_sx,pnt->p3_sy+CROSS_HEIGHT,pnt->p3_sx-CROSS_WIDTH,pnt->p3_sy);
	}
}

#endif
#endif

#if 0		//this stuff could probably just be deleted

#define DEFAULT_PERSPECTIVE_DEPTH 6

int Perspective_depth=DEFAULT_PERSPECTIVE_DEPTH;	//how many levels deep to render in perspective

int inc_perspective_depth(void)
{
	return ++Perspective_depth;

}

int dec_perspective_depth(void)
{
	return Perspective_depth==1?Perspective_depth:--Perspective_depth;

}

int reset_perspective_depth(void)
{
	return Perspective_depth = DEFAULT_PERSPECTIVE_DEPTH;

}
#endif

static ubyte code_window_point(fix x,fix y,const rect &w)
{
	ubyte code=0;

	if (x <= w.left)  code |= 1;
	if (x >= w.right) code |= 2;

	if (y <= w.top) code |= 4;
	if (y >= w.bot) code |= 8;

	return code;
}

#ifndef NDEBUG
char visited2[MAX_SEGMENTS];
#endif

namespace {

struct visited_twobit_array_t : visited_segment_multibit_array_t<2> {};

}

int	lcnt_save,scnt_save;

//Given two sides of segment, tell the two verts which form the 
//edge between them
typedef array<int_fast8_t, 2> se_array0;
typedef array<se_array0, 6> se_array1;
typedef array<se_array1, 6> se_array2;
static const se_array2 Two_sides_to_edge = {{
	{{  {{edge_none,edge_none}},	 {{3,7}},	 {{edge_none,edge_none}},	 {{2,6}},	 {{6,7}},	 {{2,3}}	}},
	{{  {{3,7}},	 {{edge_none,edge_none}},	 {{0,4}},	 {{edge_none,edge_none}},	 {{4,7}},	 {{0,3}}	}},
	{{  {{edge_none,edge_none}},	 {{0,4}},	 {{edge_none,edge_none}},	 {{1,5}},	 {{4,5}},	 {{0,1}}	}},
	{{  {{2,6}},	 {{edge_none,edge_none}},	 {{1,5}},	 {{edge_none,edge_none}},	 {{5,6}},	 {{1,2}}	}},
	{{  {{6,7}},	 {{4,7}},	 {{4,5}},	 {{5,6}},	 {{edge_none,edge_none}},	 {{edge_none,edge_none}}	}},
	{{  {{2,3}},	 {{0,3}},	 {{0,1}},	 {{1,2}},	 {{edge_none,edge_none}},	 {{edge_none,edge_none}}	}}
}};

//given an edge specified by two verts, give the two sides on that edge
typedef array<int_fast8_t, 2> es_array0;
typedef array<es_array0, 8> es_array1;
typedef array<es_array1, 8> es_array2;
static const es_array2 Edge_to_sides = {{
	{{  {{side_none,side_none}},	 {{2,5}},	 {{side_none,side_none}},	 {{1,5}},	 {{1,2}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{side_none,side_none}}	}},
	{{  {{2,5}},	 {{side_none,side_none}},	 {{3,5}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{2,3}},	 {{side_none,side_none}},	 {{side_none,side_none}}	}},
	{{  {{side_none,side_none}},	 {{3,5}},	 {{side_none,side_none}},	 {{0,5}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{0,3}},	 {{side_none,side_none}}	}},
	{{  {{1,5}},	 {{side_none,side_none}},	 {{0,5}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{0,1}}	}},
	{{  {{1,2}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{2,4}},	 {{side_none,side_none}},	 {{1,4}}	}},
	{{  {{side_none,side_none}},	 {{2,3}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{2,4}},	 {{side_none,side_none}},	 {{3,4}},	 {{side_none,side_none}}	}},
	{{  {{side_none,side_none}},	 {{side_none,side_none}},	 {{0,3}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{3,4}},	 {{side_none,side_none}},	 {{0,4}}	}},
	{{  {{side_none,side_none}},	 {{side_none,side_none}},	 {{side_none,side_none}},	 {{0,1}},	 {{1,4}},	 {{side_none,side_none}},	 {{0,4}},	 {{side_none,side_none}}	}},
}};

//@@//perform simple check on tables
//@@check_check()
//@@{
//@@	int i,j;
//@@
//@@	for (i=0;i<8;i++)
//@@		for (j=0;j<8;j++)
//@@			Assert(Edge_to_sides[i][j][0] == Edge_to_sides[j][i][0] && 
//@@					Edge_to_sides[i][j][1] == Edge_to_sides[j][i][1]);
//@@
//@@	for (i=0;i<6;i++)
//@@		for (j=0;j<6;j++)
//@@			Assert(Two_sides_to_edge[i][j][0] == Two_sides_to_edge[j][i][0] && 
//@@					Two_sides_to_edge[i][j][1] == Two_sides_to_edge[j][i][1]);
//@@
//@@
//@@}


//given an edge, tell what side is on that edge
__attribute_warn_unused_result
static int find_seg_side(const vcsegptr_t seg,const array<int, 2> &verts,unsigned notside)
{
	if (notside >= MAX_SIDES_PER_SEGMENT)
		throw std::logic_error("invalid notside");
	int side0,side1;
	int	v0,v1;

//@@	check_check();

	v0 = verts[0];
	v1 = verts[1];

	auto b = begin(seg->verts);
	auto e = end(seg->verts);
	auto iv0 = e;
	auto iv1 = e;
	for (auto i = b;;)
	{
		if (iv0 == e && *i == v0)
		{
			iv0 = i;
			if (iv1 != e)
				break;
		}
		if (iv1 == e && *i == v1)
		{
			iv1 = i;
			if (iv0 != e)
				break;
		}
		if (++i == e)
			return side_none;
	}

	const auto &eptr = Edge_to_sides[std::distance(b, iv0)][std::distance(b, iv1)];

	side0 = eptr[0];
	side1 = eptr[1];

	Assert(side0 != side_none && side1 != side_none);

	if (side0 != notside) {
		Assert(side1==notside);
		return side0;
	}
	else {
		Assert(side0==notside);
		return side1;
	}

}

__attribute_warn_unused_result
static bool compare_child(const vcsegptridx_t seg, const vcsegptridx_t cseg, const sidenum_fast_t edgeside)
{
	const auto &cside = cseg->sides[edgeside];
	const auto &sv = Side_to_verts[edgeside][cside.get_type() == SIDE_IS_TRI_13 ? 1 : 0];
	const auto &temp = vm_vec_sub(Viewer_eye, Vertices[seg->verts[sv]]);
	const auto &cnormal = cseg->sides[edgeside].normals;
	return vm_vec_dot(cnormal[0], temp) < 0 || vm_vec_dot(cnormal[1], temp) < 0;
}

//see if the order matters for these two children.
//returns 0 if order doesn't matter, 1 if c0 before c1, -1 if c1 before c0
__attribute_warn_unused_result
static bool compare_children(const vcsegptridx_t seg, sidenum_fast_t s0, sidenum_fast_t s1)
{
	Assert(s0 != side_none && s1 != side_none);

	if (Side_opposite[s0] == s1)
		return false;
	//find normals of adjoining sides
	const array<int, 2> edge_verts = {
		{seg->verts[Two_sides_to_edge[s0][s1][0]], seg->verts[Two_sides_to_edge[s0][s1][1]]}
	};
	if (edge_verts[0] == -1 || edge_verts[1] == -1)
		throw std::logic_error("invalid edge vert");
	auto seg0 = vsegptridx(seg->children[s0]);
	auto edgeside0 = find_seg_side(seg0,edge_verts,find_connect_side(seg,seg0));
	if (edgeside0 == side_none)
		return false;
	auto r0 = compare_child(seg, seg0, edgeside0);
	if (!r0)
		return r0;
	auto seg1 = vsegptridx(seg->children[s1]);
	auto edgeside1 = find_seg_side(seg1,edge_verts,find_connect_side(seg,seg1));
	if (edgeside1 == side_none)
		return false;
	return !compare_child(seg, seg1, edgeside1);
}

//short the children of segment to render in the correct order
//returns non-zero if swaps were made
typedef array<sidenum_fast_t, MAX_SIDES_PER_SEGMENT> sort_child_array_t;
static void sort_seg_children(const vcsegptridx_t seg, const partial_range_t<sort_child_array_t::iterator> &r)
{
	//for each child,  compare with other children and see if order matters
	//if order matters, fix if wrong
	auto predicate = [seg](sidenum_fast_t a, sidenum_fast_t b)
	{
		return compare_children(seg, a, b);
	};
		std::sort(r.begin(), r.end(), predicate);
}

static void add_obj_to_seglist(render_state_t &rstate, objnum_t objnum, segnum_t segnum)
{
	auto p = rstate.render_seg_map.emplace(segnum, render_state_t::per_segment_state_t{});
	auto &o = p.first->second.objects;
	if (p.second)
		o.reserve(16);
	o.emplace_back(render_state_t::per_segment_state_t::distant_object{objnum});
}

namespace {

class render_compare_context_t
{
	struct element
	{
		fix64 dist_squared;
#if defined(DXX_BUILD_DESCENT_II)
		object *objp;
#endif
	};
	typedef array<element, MAX_OBJECTS> array_t;
	array_t a;
public:
	array_t::reference operator[](std::size_t i) { return a[i]; }
	array_t::const_reference operator[](std::size_t i) const { return a[i]; }
	render_compare_context_t(const render_state_t::per_segment_state_t &segstate)
	{
		range_for (const auto t, segstate.objects)
		{
			const auto &&objp = vobjptr(t.objnum);
			auto &e = (*this)[t.objnum];
#if defined(DXX_BUILD_DESCENT_II)
			e.objp = objp;
#endif
			e.dist_squared = vm_vec_dist2(objp->pos, Viewer_eye);
		}
	}
};

}

//compare function for object sort. 
static bool compare_func(const render_compare_context_t &c, const render_state_t::per_segment_state_t::distant_object &a,const render_state_t::per_segment_state_t::distant_object &b)
{
	fix64 delta_dist_squared = c[a.objnum].dist_squared - c[b.objnum].dist_squared;

#if defined(DXX_BUILD_DESCENT_II)
	const auto obj_a = c[a.objnum].objp;
	const auto obj_b = c[b.objnum].objp;

	auto abs_delta_dist_squared = std::abs(delta_dist_squared);
	fix combined_size = obj_a->size + obj_b->size;
	/*
	 * First check without squaring.  If true, the square can be
	 * skipped.
	 */
	if (abs_delta_dist_squared < combined_size || abs_delta_dist_squared < (combined_size * combined_size))
	{		//same position

		//these two objects are in the same position.  see if one is a fireball
		//or laser or something that should plot on top.  Don't do this for
		//the afterburner blobs, though.

		if (obj_a->type == OBJ_WEAPON || (obj_a->type == OBJ_FIREBALL && obj_a->id != VCLIP_AFTERBURNER_BLOB))
		{
			if (!(obj_b->type == OBJ_WEAPON || obj_b->type == OBJ_FIREBALL))
				return true;	//a is weapon, b is not, so say a is closer
			//both are weapons 
		}
		else
		{
			if (obj_b->type == OBJ_WEAPON || (obj_b->type == OBJ_FIREBALL && obj_b->id != VCLIP_AFTERBURNER_BLOB))
				return false;	//b is weapon, a is not, so say a is farther
		}

		//no special case, fall through to normal return
	}
#endif
	return delta_dist_squared < 0;	//return distance
}

static void sort_segment_object_list(render_state_t::per_segment_state_t &segstate)
{
	render_compare_context_t context(segstate);
	typedef render_state_t::per_segment_state_t::distant_object distant_object;
	const auto predicate = [&context](const distant_object &a, const distant_object &b) { return compare_func(context, a, b); };
	auto &v = segstate.objects;
	std::sort(v.begin(), v.end(), predicate);
}

static void build_object_lists(render_state_t &rstate)
{
	int nn;
	for (nn=0;nn < rstate.N_render_segs;nn++) {
		auto segnum = rstate.Render_list[nn];
		if (segnum != segment_none) {
			range_for (const auto obj, objects_in(Segments[segnum]))
			{
				int list_pos;
				if (obj->type == OBJ_NONE)
					continue;

				Assert( obj->segnum == segnum );

				if (obj->flags & OF_ATTACHED)
					continue;		//ignore this object

				auto new_segnum = segnum;
				list_pos = nn;

#if defined(DXX_BUILD_DESCENT_I)
				int did_migrate;
				if (obj->type != OBJ_CNTRLCEN)		//don't migrate controlcen
#elif defined(DXX_BUILD_DESCENT_II)
				const int did_migrate = 0;
				if (obj->type != OBJ_CNTRLCEN && !(obj->type==OBJ_ROBOT && get_robot_id(obj)==65))		//don't migrate controlcen
#endif
				do {
					segmasks m;

#if defined(DXX_BUILD_DESCENT_I)
					did_migrate = 0;
#endif
					m = get_seg_masks(obj->pos, vcsegptr(new_segnum), obj->size);
	
					if (m.sidemask) {
						int sn,sf;

						for (sn=0,sf=1;sn<6;sn++,sf<<=1)
							if (m.sidemask & sf) {
#if defined(DXX_BUILD_DESCENT_I)
								const auto &&seg = vcsegptr(obj->segnum);
#elif defined(DXX_BUILD_DESCENT_II)
								const auto &&seg = vcsegptr(new_segnum);
#endif
		
								if (WALL_IS_DOORWAY(seg,sn) & WID_FLY_FLAG) {		//can explosion migrate through
									int child = seg->children[sn];
									int checknp;
		
									for (checknp=list_pos;checknp--;)
										if (rstate.Render_list[checknp] == child) {
											new_segnum = child;
											list_pos = checknp;
#if defined(DXX_BUILD_DESCENT_I)
											did_migrate = 1;
#endif
										}
								}
							}
					}
	
				} while (did_migrate);
				add_obj_to_seglist(rstate, obj, new_segnum);
			}

		}
	}

	//now that there's a list for each segment, sort the items in those lists
	range_for (const auto segnum, partial_range(rstate.Render_list, rstate.N_render_segs))
	{
		if (segnum != segment_none) {
			sort_segment_object_list(rstate.render_seg_map[segnum]);
		}
	}
}

//--unused-- int Total_num_tmaps_drawn=0;

int Rear_view=0;

#ifdef JOHN_ZOOM
fix Zoom_factor=F1_0;
#endif
//renders onto current canvas
void render_frame(fix eye_offset, window_rendered_data &window)
{
	if (Endlevel_sequence) {
		render_endlevel_frame(eye_offset);
		return;
	}

	if ( Newdemo_state == ND_STATE_RECORDING && eye_offset >= 0 )	{
     
      if (RenderingType==0)
   		newdemo_record_start_frame(FrameTime );
      if (RenderingType!=255)
   		newdemo_record_viewer_object(vobjptridx(Viewer));
	}
  
   //Here:

	start_lighting_frame(Viewer);		//this is for ugly light-smoothing hack
  
	g3_start_frame();

	Viewer_eye = Viewer->pos;

//	if (Viewer->type == OBJ_PLAYER && (PlayerCfg.CockpitMode[1]!=CM_REAR_VIEW))
//		vm_vec_scale_add2(&Viewer_eye,&Viewer->orient.fvec,(Viewer->size*3)/4);

	if (eye_offset)	{
		vm_vec_scale_add2(Viewer_eye,Viewer->orient.rvec,eye_offset);
	}

	#ifdef EDITOR
	if (EditorWindow)
		Viewer_eye = Viewer->pos;
	#endif

	auto start_seg_num = find_point_seg(Viewer_eye,Viewer->segnum);

	if (start_seg_num==segment_none)
		start_seg_num = Viewer->segnum;

	if (Rear_view && (Viewer==ConsoleObject)) {
		vms_angvec Player_head_angles;
		Player_head_angles.p = Player_head_angles.b = 0;
		Player_head_angles.h = 0x7fff;
		const auto &&headm = vm_angles_2_matrix(Player_head_angles);
		const auto viewm = vm_matrix_x_matrix(Viewer->orient,headm);
		g3_set_view_matrix(Viewer_eye,viewm,Render_zoom);
	} else	{
#ifdef JOHN_ZOOM
		if (keyd_pressed[KEY_RSHIFT] )	{
			Zoom_factor += FrameTime*4;
			if (Zoom_factor > F1_0*5 ) Zoom_factor=F1_0*5;
		} else {
			Zoom_factor -= FrameTime*4;
			if (Zoom_factor < F1_0 ) Zoom_factor = F1_0;
		}
		g3_set_view_matrix(Viewer_eye,Viewer->orient,fixdiv(Render_zoom,Zoom_factor));
#else
		g3_set_view_matrix(Viewer_eye,Viewer->orient,Render_zoom);
#endif
	}

	if (Clear_window == 1) {
		if (Clear_window_color == -1)
			Clear_window_color = BM_XRGB(0, 0, 0);	//BM_XRGB(31, 15, 7);
		gr_clear_canvas(Clear_window_color);
	}
#if defined(DXX_BUILD_DESCENT_II)
	#ifndef NDEBUG
	if (Show_only_curside)
		gr_clear_canvas(Clear_window_color);
	#endif
#endif

	render_mine(start_seg_num, eye_offset, window);

	g3_end_frame();

   //RenderingType=0;

	// -- Moved from here by MK, 05/17/95, wrong if multiple renders/frame! FrameCount++;		//we have rendered a frame
}

static unsigned first_terminal_seg;

#if defined(DXX_BUILD_DESCENT_II)
void update_rendered_data(window_rendered_data &window, const vobjptr_t viewer, int rear_view_flag)
{
	window.time = timer_query();
	window.viewer = viewer;
	window.rear_view = rear_view_flag;
}
#endif

//build a list of segments to be rendered
//fills in Render_list & N_render_segs
static void build_segment_list(render_state_t &rstate, visited_twobit_array_t &visited, short start_seg_num)
{
	int	lcnt,scnt,ecnt;
	int	l;

	rstate.render_pos.fill(-1);

	#ifndef NDEBUG
	memset(visited2, 0, sizeof(visited2[0])*(Highest_segment_index+1));
	#endif

	lcnt = scnt = 0;

	rstate.Render_list[lcnt] = start_seg_num;
	visited[start_seg_num]=1;
	lcnt++;
	ecnt = lcnt;
	rstate.render_pos[start_seg_num] = 0;
	{
		auto &rsm_start_seg = rstate.render_seg_map[start_seg_num];
		auto &rw = rsm_start_seg.render_window;
		rw.left = rw.top = 0;
		rw.right = grd_curcanv->cv_bitmap.bm_w-1;
		rw.bot = grd_curcanv->cv_bitmap.bm_h-1;
	}

	//breadth-first renderer

	//build list

	for (l=0;l<Render_depth;l++) {
		for (scnt=0;scnt < ecnt;scnt++) {
			auto segnum = rstate.Render_list[scnt];
			if (segnum == segment_none) continue;

			auto &srsm = rstate.render_seg_map[segnum];
			auto &processed = srsm.processed;
			if (processed)
				continue;
			const auto &check_w = srsm.render_window;

			processed = true;

			auto seg = vsegptridx(segnum);
			const auto r = rotate_list(seg->verts);

			//look at all sides of this segment.
			//tricky code to look at sides in correct order follows

			sort_child_array_t child_list;		//list of ordered sides to process
			uint_fast32_t n_children = 0;							//how many sides in child_list
			for (uint_fast32_t c = 0;c < MAX_SIDES_PER_SEGMENT;c++) {		//build list of sides
				auto wid = WALL_IS_DOORWAY(seg, c);
				if (wid & WID_RENDPAST_FLAG)
				{
					ubyte codes_and = r.uor;
					if (codes_and & CC_BEHIND)
					{
						range_for (const auto i, Side_to_verts[c])
							codes_and &= Segment_points[seg->verts[i]].p3_codes;
						if (codes_and & CC_BEHIND) continue;
					}
					child_list[n_children++] = c;
				}
			}
			if (!n_children)
				continue;

			//now order the sides in some magical way
			const auto child_range = partial_range(child_list, n_children);
			sort_seg_children(seg, child_range);
			project_list(seg->verts);
			range_for (const auto siden, child_range)
			{
				auto ch=seg->children[siden];
				{
					{
						short min_x=32767,max_x=-32767,min_y=32767,max_y=-32767;
						int no_proj_flag=0;	//a point wasn't projected
						uint8_t codes_and_3d = 0xff, codes_and_2d = codes_and_3d;
						range_for (const auto i, Side_to_verts[siden])
						{
							g3s_point *pnt = &Segment_points[seg->verts[i]];

							if (! (pnt->p3_flags&PF_PROJECTED)) {no_proj_flag=1; break;}

							const int16_t _x = f2i(pnt->p3_sx), _y = f2i(pnt->p3_sy);

							if (_x < min_x) min_x = _x;
							if (_x > max_x) max_x = _x;

							if (_y < min_y) min_y = _y;
							if (_y > max_y) max_y = _y;
							codes_and_3d &= pnt->p3_codes;
							codes_and_2d &= code_window_point(_x,_y,check_w);
						}
						if (no_proj_flag || (!codes_and_3d && !codes_and_2d)) {	//maybe add this segment
							auto rp = rstate.render_pos[ch];
							rect nw;

							if (no_proj_flag)
								nw = check_w;
							else {
								nw.left  = max(check_w.left,min_x);
								nw.right = min(check_w.right,max_x);
								nw.top   = max(check_w.top,min_y);
								nw.bot   = min(check_w.bot,max_y);
							}

							//see if this seg already visited, and if so, does current window
							//expand the old window?
							if (rp != -1) {
								auto &old_w = rstate.render_seg_map[rstate.Render_list[rp]].render_window;
								if (nw.left < old_w.left ||
										 nw.top < old_w.top ||
										 nw.right > old_w.right ||
										 nw.bot > old_w.bot) {

									nw.left  = min(nw.left, old_w.left);
									nw.right = max(nw.right, old_w.right);
									nw.top   = min(nw.top, old_w.top);
									nw.bot   = max(nw.bot, old_w.bot);

									{
										//no_render_flag[lcnt] = 1;
										rstate.render_seg_map[ch].processed = false;		//force reprocess
										rstate.Render_list[lcnt] = segment_none;
										old_w = nw;		//get updated window
										goto no_add;
									}
								}
								else goto no_add;
							}
							rstate.render_pos[ch] = lcnt;
							rstate.Render_list[lcnt] = ch;
							{
								auto &chrsm = rstate.render_seg_map[ch];
								chrsm.Seg_depth = l;
								chrsm.render_window = nw;
							}
							lcnt++;
							if (lcnt >= MAX_RENDER_SEGS) {goto done_list;}
							visited[ch] = 1;
no_add:
	;

						}
					}
				}
			}
		}

		scnt = ecnt;
		ecnt = lcnt;

	}
done_list:

	lcnt_save = lcnt;
	scnt_save = scnt;

	first_terminal_seg = scnt;
	rstate.N_render_segs = lcnt;

}

//renders onto current canvas
void render_mine(segnum_t start_seg_num,fix eye_offset, window_rendered_data &window)
{
	using std::advance;
	render_state_t rstate;
	#ifndef NDEBUG
	object_rendered = {};
	#endif

	//set up for rendering

	render_start_frame();

	visited_twobit_array_t visited;

	#if defined(EDITOR)
	if (Show_only_curside) {
		rotate_list(Cursegp->verts);
		render_side(Cursegp,Curside);
		return;
	}
	#endif


	#ifdef EDITOR
#if defined(DXX_BUILD_DESCENT_I)
	if (_search_mode || eye_offset>0)
#elif defined(DXX_BUILD_DESCENT_II)
	if (_search_mode)
#endif
	{
		//lcnt = lcnt_save;
		//scnt = scnt_save;
	}
	else
	#endif
		//NOTE LINK TO ABOVE!!
		build_segment_list(rstate, visited, start_seg_num);		//fills in Render_list & N_render_segs

	const auto render_range = partial_range(rstate.Render_list, rstate.N_render_segs);
	const auto &&reversed_render_range = render_range.reversed();
	//render away
	#ifndef NDEBUG
#if defined(DXX_BUILD_DESCENT_I)
	if (!(_search_mode || eye_offset>0))
#elif defined(DXX_BUILD_DESCENT_II)
	if (!(_search_mode))
#endif
	{
		range_for (const auto segnum, render_range)
		{
			if (segnum != segment_none)
			{
				if (visited2[segnum])
					Int3();		//get Matt
				else
					visited2[segnum] = 1;
			}
		}
	}
	#endif

	if (!(_search_mode))
		build_object_lists(rstate);

	if (eye_offset<=0) // Do for left eye or zero.
		set_dynamic_light(rstate);

	if (reversed_render_range.empty())
		/* Impossible, but later code has undefined behavior if this
		 * happens
		 */
		return;

	if (!_search_mode && Clear_window == 2) {
		if (first_terminal_seg < rstate.N_render_segs) {
			if (Clear_window_color == -1)
				Clear_window_color = BM_XRGB(0, 0, 0);	//BM_XRGB(31, 15, 7);
	
			gr_setcolor(Clear_window_color);
	
			range_for (const auto segnum, partial_range(rstate.Render_list, first_terminal_seg, rstate.N_render_segs))
			{
				if (segnum != segment_none) {
					const auto &rw = rstate.render_seg_map[segnum].render_window;
					#ifndef NDEBUG
					if (rw.left == -1 || rw.top == -1 || rw.right == -1 || rw.bot == -1)
						Int3();
					else
					#endif
						//NOTE LINK TO ABOVE!
						gr_rect(rw.left, rw.top, rw.right, rw.bot);
				}
			}
		}
	}
#ifndef OGL
	range_for (const auto segnum, reversed_render_range)
	{
		// Interpolation_method = 0;
		auto &srsm = rstate.render_seg_map[segnum];

		//if (!no_render_flag[nn])
		if (segnum!=segment_none && (_search_mode || visited[segnum]!=3)) {
			//set global render window vars

			Current_seg_depth = srsm.Seg_depth;
			{
				const auto &rw = srsm.render_window;
				Window_clip_left  = rw.left;
				Window_clip_top   = rw.top;
				Window_clip_right = rw.right;
				Window_clip_bot   = rw.bot;
			}

			render_segment(vcsegptridx(segnum));
			visited[segnum]=3;
			if (srsm.objects.empty())
				continue;

			{		//reset for objects
				Window_clip_left  = Window_clip_top = 0;
				Window_clip_right = grd_curcanv->cv_bitmap.bm_w-1;
				Window_clip_bot   = grd_curcanv->cv_bitmap.bm_h-1;
			}

			{
				//int n_expl_objs=0,expl_objs[5],i;
				const auto save_linear_depth = exchange(Max_linear_depth, Max_linear_depth_objects);
				range_for (auto &v, srsm.objects)
				{
					do_render_object(v.objnum, window);	// note link to above else
				}
				Max_linear_depth = save_linear_depth;
			}

		}
	}
#else
	struct render_subrange : partial_range_t<std::reverse_iterator<segnum_t *>>
	{
		iterator *m_pbegin;
		render_subrange(iterator i) :
			partial_range_t<iterator>(i, std::prev(i)),
			m_pbegin(&m_begin)
		{
		}
		/* Prevent pointing m_pbegin at m_begin of different instance */
		render_subrange(const render_subrange &rhs) = delete;
		render_subrange &operator=(const render_subrange &rhs) = delete;
		void record(iterator p, iterator &dummy)
		{
			*m_pbegin = m_end = p;
			m_pbegin = &dummy;
		}
	};
	struct render_ranges
	{
		typedef render_subrange::iterator iterator;
		iterator dummy_write_only_begin;
		render_subrange reversed_object_render_range, reversed_alpha_segment_render_range;
		render_ranges(iterator e) :
			reversed_object_render_range(e),
			reversed_alpha_segment_render_range(e)
		{
		}
		void record_object(iterator p)
		{
			reversed_object_render_range.record(p, dummy_write_only_begin);
		}
		void record_alpha(iterator p)
		{
			reversed_alpha_segment_render_range.record(p, dummy_write_only_begin);
		}
	};
	/* Initially empty */
	render_ranges rr{reversed_render_range.end()};
	// Sorting elements for Alpha - 3 passes
	// First Pass: render opaque level geometry + transculent level geometry with high Alpha-Test func
	for (auto iter = reversed_render_range.begin(); iter != reversed_render_range.end(); ++iter)
	{
		const auto segnum = *iter;
		auto &srsm = rstate.render_seg_map[segnum];

#if defined(DXX_BUILD_DESCENT_I)
		if (segnum!=segment_none && (_search_mode || eye_offset>0 || visited[segnum]!=3))
#elif defined(DXX_BUILD_DESCENT_II)
		if (segnum!=segment_none && (_search_mode || visited[segnum]!=3))
#endif
		{
			Current_seg_depth = srsm.Seg_depth;
			if (!srsm.objects.empty())
				rr.record_object(iter);
			//set global render window vars

			{
				const auto &rw = srsm.render_window;
				Window_clip_left  = rw.left;
				Window_clip_top   = rw.top;
				Window_clip_right = rw.right;
				Window_clip_bot   = rw.bot;
			}

			// render segment
			{
				const auto &&seg = vcsegptridx(segnum);
				int			sn;
				Assert(segnum!=segment_none && segnum<=Highest_segment_index);
				g3s_codes 	cc=rotate_list(seg->verts);

				if (! cc.uand) {		//all off screen?

				  if (Viewer->type!=OBJ_ROBOT)
					Automap_visited[segnum]=1;

					for (sn=0; sn<MAX_SIDES_PER_SEGMENT; sn++)
					{
						auto wid = WALL_IS_DOORWAY(seg, sn);
						if (wid == WID_TRANSPARENT_WALL || wid == WID_TRANSILLUSORY_WALL
#if defined(DXX_BUILD_DESCENT_II)
							|| (wid & WID_CLOAKED_FLAG)
#endif
							)
						{
							glAlphaFunc(GL_GEQUAL,0.8);
							render_side(seg, sn);
							glAlphaFunc(GL_GEQUAL,0.02);
							rr.record_alpha(iter);
						}
						else
							render_side(seg, sn);
					}
				}
			}
			visited[segnum]=3;
		}
	}

	visited.clear();

	// Second Pass: Objects
	advance(rr.reversed_object_render_range.m_end, 1);
	range_for (const auto segnum, rr.reversed_object_render_range)
	{
		auto &srsm = rstate.render_seg_map[segnum];
		if (srsm.objects.empty())
			continue;

#if defined(DXX_BUILD_DESCENT_I)
		if (segnum!=segment_none && (_search_mode || eye_offset>0 || visited[segnum]!=3))
#elif defined(DXX_BUILD_DESCENT_II)
		if (segnum!=segment_none && (_search_mode || visited[segnum]!=3))
#endif
		{
			Current_seg_depth = srsm.Seg_depth;
			//set global render window vars

			visited[segnum]=3;

			{		//reset for objects
				Window_clip_left  = Window_clip_top = 0;
				Window_clip_right = grd_curcanv->cv_bitmap.bm_w-1;
				Window_clip_bot   = grd_curcanv->cv_bitmap.bm_h-1;
			}

			// render objects
			{
				range_for (auto &v, srsm.objects)
				{
					do_render_object(v.objnum, window);	// note link to above else
				}
			}
		}
	}

	visited.clear();

	// Third Pass - Render Transculent level geometry with normal Alpha-Func
	advance(rr.reversed_alpha_segment_render_range.m_end, 1);
	range_for (const auto segnum, rr.reversed_alpha_segment_render_range)
	{
		auto &srsm = rstate.render_seg_map[segnum];

#if defined(DXX_BUILD_DESCENT_I)
		if (segnum!=segment_none && (_search_mode || eye_offset>0 || visited[segnum]!=3))
#elif defined(DXX_BUILD_DESCENT_II)
		if (segnum!=segment_none && (_search_mode || visited[segnum]!=3))
#endif
		{
			Current_seg_depth = srsm.Seg_depth;
			//set global render window vars

			{
				const auto &rw = srsm.render_window;
				Window_clip_left  = rw.left;
				Window_clip_top   = rw.top;
				Window_clip_right = rw.right;
				Window_clip_bot   = rw.bot;
			}

			// render segment
			{
				const auto &&seg = vcsegptridx(segnum);
				int			sn;
				Assert(segnum!=segment_none && segnum<=Highest_segment_index);
				g3s_codes 	cc=rotate_list(seg->verts);

				if (! cc.uand) {		//all off screen?
					for (sn=0; sn<MAX_SIDES_PER_SEGMENT; sn++)
					{
						auto wid = WALL_IS_DOORWAY(seg, sn);
						if (wid == WID_TRANSPARENT_WALL || wid == WID_TRANSILLUSORY_WALL
#if defined(DXX_BUILD_DESCENT_II)
							|| (wid & WID_CLOAKED_FLAG)
#endif
							)
							render_side(seg, sn);
					}
				}
			}
			visited[segnum]=3;
		}
	}
#endif

	// -- commented out by mk on 09/14/94...did i do a good thing??  object_render_targets();

#ifdef EDITOR
	#ifndef NDEBUG
	//draw curedge stuff
	if (Outline_mode) outline_seg_side(Cursegp,Curside,Curedge,Curvert);
	#endif
#endif
}
#ifdef EDITOR
//finds what segment is at a given x&y -  seg,side,face are filled in
//works on last frame rendered. returns true if found
//if seg<0, then an object was found, and the object number is -seg-1
int find_seg_side_face(short x,short y,segnum_t &seg,objnum_t &obj,int &side,int &face,int &poly)
{
	_search_mode = -1;

	_search_x = x; _search_y = y;

	found_seg = segment_none;
	found_obj = object_none;

	if (render_3d_in_big_window) {
		gr_set_current_canvas(LargeView.ev_canv);
	}
	else {
		gr_set_current_canvas(Canv_editor_game);
	}
	render_frame(0);

	_search_mode = 0;

	seg = found_seg;
	obj = found_obj;
	side = found_side;
	face = found_face;
	poly = found_poly;
	return found_seg != segment_none || found_obj != object_none;
}
#endif