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/*

Copyright (C) 1996-1997 Id Software, Inc.

This program is free software; you can redistribute it and/or

modify it under the terms of the GNU General Public License

as published by the Free Software Foundation; either version 2

of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

// r_edge.c

#include "quakedef.h"

#include "r_local.h"

#if 0

// FIXME

the complex cases add new polys on most lines, so dont optimize for keeping them the same

have multiple free span lists to try to get better coherence?

low depth complexity -- 1 to 3 or so

this breaks spans at every edge, even hidden ones (bad)

have a sentinal at both ends?

#endif

edge_t	*auxedges;

edge_t	*r_edges, *edge_p, *edge_max;

surf_t	*surfaces, *surface_p, *surf_max;

// surfaces are generated in back to front order by the bsp, so if a surf

// pointer is greater than another one, it should be drawn in front

// surfaces[1] is the background, and is used as the active surface stack

edge_t	*newedges[MAXHEIGHT];

edge_t	*removeedges[MAXHEIGHT];

espan_t	*span_p, *max_span_p;

int		r_currentkey;

extern	int	screenwidth;

int	current_iv;

int	edge_head_u_shift20, edge_tail_u_shift20;

static void (*pdrawfunc)(void);

edge_t	edge_head;

edge_t	edge_tail;

edge_t	edge_aftertail;

edge_t	edge_sentinel;

float	fv;

void R_GenerateSpans (void);

void R_GenerateSpansBackward (void);

void R_LeadingEdge (edge_t *edge);

void R_LeadingEdgeBackwards (edge_t *edge);

void R_TrailingEdge (surf_t *surf, edge_t *edge);

//=============================================================================

/*

==============

R_DrawCulledPolys

==============

*/

void R_DrawCulledPolys (void)

{

	surf_t			*s;

	msurface_t		*pface;

	currententity = &cl_entities[0];

	if (r_worldpolysbacktofront)

	{

		for (s=surface_p-1 ; s>&surfaces[1] ; s--)

		{

			if (!s->spans)

				continue;

			if (!(s->flags & SURF_DRAWBACKGROUND))

			{

				pface = (msurface_t *)s->data;

				R_RenderPoly (pface, 15);

			}

		}

	}

	else

	{

		for (s = &surfaces[1] ; s

		{

			if (!s->spans)

				continue;

			if (!(s->flags & SURF_DRAWBACKGROUND))

			{

				pface = (msurface_t *)s->data;

				R_RenderPoly (pface, 15);

			}

		}

	}

}

/*

==============

R_BeginEdgeFrame

==============

*/

void R_BeginEdgeFrame (void)

{

	int		v;

	edge_p = r_edges;

	edge_max = &r_edges[r_numallocatededges];

	surface_p = &surfaces[2];	// background is surface 1,

								//  surface 0 is a dummy

	surfaces[1].spans = NULL;	// no background spans yet

	surfaces[1].flags = SURF_DRAWBACKGROUND;

// put the background behind everything in the world

	if (r_draworder.value)

	{

		pdrawfunc = R_GenerateSpansBackward;

		surfaces[1].key = 0;

		r_currentkey = 1;

	}

	else

	{

		pdrawfunc = R_GenerateSpans;

		surfaces[1].key = 0x7FFFFFFF;

		r_currentkey = 0;

	}

// FIXME: set with memset

	for (v=r_refdef.vrect.y ; v

	{

		newedges[v] = removeedges[v] = NULL;

	}

}

#if	!id386

/*

==============

R_InsertNewEdges

Adds the edges in the linked list edgestoadd, adding them to the edges in the

linked list edgelist.  edgestoadd is assumed to be sorted on u, and non-empty (this is actually newedges[v]).  edgelist is assumed to be sorted on u, with a

sentinel at the end (actually, this is the active edge table starting at

edge_head.next).

==============

*/

void R_InsertNewEdges (edge_t *edgestoadd, edge_t *edgelist)

{

	edge_t	*next_edge;

	do

	{

		next_edge = edgestoadd->next;

edgesearch:

		if (edgelist->u >= edgestoadd->u)

			goto addedge;

		edgelist=edgelist->next;

		if (edgelist->u >= edgestoadd->u)

			goto addedge;

		edgelist=edgelist->next;

		if (edgelist->u >= edgestoadd->u)

			goto addedge;

		edgelist=edgelist->next;

		if (edgelist->u >= edgestoadd->u)

			goto addedge;

		edgelist=edgelist->next;

		goto edgesearch;

	// insert edgestoadd before edgelist

addedge:

		edgestoadd->next = edgelist;

		edgestoadd->prev = edgelist->prev;

		edgelist->prev->next = edgestoadd;

		edgelist->prev = edgestoadd;

	} while ((edgestoadd = next_edge) != NULL);

}

#endif	// !id386

#if	!id386

/*

==============

R_RemoveEdges

==============

*/

void R_RemoveEdges (edge_t *pedge)

{

	do

	{

		pedge->next->prev = pedge->prev;

		pedge->prev->next = pedge->next;

	} while ((pedge = pedge->nextremove) != NULL);

}

#endif	// !id386

#if	!id386

/*

==============

R_StepActiveU

==============

*/

void R_StepActiveU (edge_t *pedge)

{

	edge_t		*pnext_edge, *pwedge;

	while (1)

	{

nextedge:

		pedge->u += pedge->u_step;

		if (pedge->u < pedge->prev->u)

			goto pushback;

		pedge = pedge->next;

		pedge->u += pedge->u_step;

		if (pedge->u < pedge->prev->u)

			goto pushback;

		pedge = pedge->next;

		pedge->u += pedge->u_step;

		if (pedge->u < pedge->prev->u)

			goto pushback;

		pedge = pedge->next;

		pedge->u += pedge->u_step;

		if (pedge->u < pedge->prev->u)

			goto pushback;

		pedge = pedge->next;

		goto nextedge;

pushback:

		if (pedge == &edge_aftertail)

			return;

	// push it back to keep it sorted

		pnext_edge = pedge->next;

	// pull the edge out of the edge list

		pedge->next->prev = pedge->prev;

		pedge->prev->next = pedge->next;

	// find out where the edge goes in the edge list

		pwedge = pedge->prev->prev;

		while (pwedge->u > pedge->u)

		{

			pwedge = pwedge->prev;

		}

	// put the edge back into the edge list

		pedge->next = pwedge->next;

		pedge->prev = pwedge;

		pedge->next->prev = pedge;

		pwedge->next = pedge;

		pedge = pnext_edge;

		if (pedge == &edge_tail)

			return;

	}

}

#endif	// !id386

/*

==============

R_CleanupSpan

==============

*/

void R_CleanupSpan ()

{

	surf_t	*surf;

	int		iu;

	espan_t	*span;

// now that we've reached the right edge of the screen, we're done with any

// unfinished surfaces, so emit a span for whatever's on top

	surf = surfaces[1].next;

	iu = edge_tail_u_shift20;

	if (iu > surf->last_u)

	{

		span = span_p++;

		span->u = surf->last_u;

		span->count = iu - span->u;

		span->v = current_iv;

		span->pnext = surf->spans;

		surf->spans = span;

	}

// reset spanstate for all surfaces in the surface stack

	do

	{

		surf->spanstate = 0;

		surf = surf->next;

	} while (surf != &surfaces[1]);

}

/*

==============

R_LeadingEdgeBackwards

==============

*/

void R_LeadingEdgeBackwards (edge_t *edge)

{

	espan_t			*span;

	surf_t			*surf, *surf2;

	int				iu;

// it's adding a new surface in, so find the correct place

	surf = &surfaces[edge->surfs[1]];

// don't start a span if this is an inverted span, with the end

// edge preceding the start edge (that is, we've already seen the

// end edge)

	if (++surf->spanstate == 1)

	{

		surf2 = surfaces[1].next;

		if (surf->key > surf2->key)

			goto newtop;

	// if it's two surfaces on the same plane, the one that's already

	// active is in front, so keep going unless it's a bmodel

		if (surf->insubmodel && (surf->key == surf2->key))

		{

		// must be two bmodels in the same leaf; don't care, because they'll

		// never be farthest anyway

			goto newtop;

		}

continue_search:

		do

		{

			surf2 = surf2->next;

		} while (surf->key < surf2->key);

		if (surf->key == surf2->key)

		{

		// if it's two surfaces on the same plane, the one that's already

		// active is in front, so keep going unless it's a bmodel

			if (!surf->insubmodel)

				goto continue_search;

		// must be two bmodels in the same leaf; don't care which is really

		// in front, because they'll never be farthest anyway

		}

		goto gotposition;

newtop:

	// emit a span (obscures current top)

		iu = edge->u >> 20;

		if (iu > surf2->last_u)

		{

			span = span_p++;

			span->u = surf2->last_u;

			span->count = iu - span->u;

			span->v = current_iv;

			span->pnext = surf2->spans;

			surf2->spans = span;

		}

		// set last_u on the new span

		surf->last_u = iu;

gotposition:

	// insert before surf2

		surf->next = surf2;

		surf->prev = surf2->prev;

		surf2->prev->next = surf;

		surf2->prev = surf;

	}

}

/*

==============

R_TrailingEdge

==============

*/

void R_TrailingEdge (surf_t *surf, edge_t *edge)

{

	espan_t			*span;

	int				iu;

// don't generate a span if this is an inverted span, with the end

// edge preceding the start edge (that is, we haven't seen the

// start edge yet)

	if (--surf->spanstate == 0)

	{

		if (surf->insubmodel)

			r_bmodelactive--;

		if (surf == surfaces[1].next)

		{

		// emit a span (current top going away)

			iu = edge->u >> 20;

			if (iu > surf->last_u)

			{

				span = span_p++;

				span->u = surf->last_u;

				span->count = iu - span->u;

				span->v = current_iv;

				span->pnext = surf->spans;

				surf->spans = span;

			}

		// set last_u on the surface below

			surf->next->last_u = iu;

		}

		surf->prev->next = surf->next;

		surf->next->prev = surf->prev;

	}

}

#if	!id386

/*

==============

R_LeadingEdge

==============

*/

void R_LeadingEdge (edge_t *edge)

{

	espan_t			*span;

	surf_t			*surf, *surf2;

	int				iu;

	double			fu, newzi, testzi, newzitop, newzibottom;

	if (edge->surfs[1])

	{

	// it's adding a new surface in, so find the correct place

		surf = &surfaces[edge->surfs[1]];

	// don't start a span if this is an inverted span, with the end

	// edge preceding the start edge (that is, we've already seen the

	// end edge)

		if (++surf->spanstate == 1)

		{

			if (surf->insubmodel)

				r_bmodelactive++;

			surf2 = surfaces[1].next;

			if (surf->key < surf2->key)

				goto newtop;

		// if it's two surfaces on the same plane, the one that's already

		// active is in front, so keep going unless it's a bmodel

			if (surf->insubmodel && (surf->key == surf2->key))

			{

			// must be two bmodels in the same leaf; sort on 1/z

				fu = (float)(edge->u - 0xFFFFF) * (1.0 / 0x100000);

				newzi = surf->d_ziorigin + fv*surf->d_zistepv +

						fu*surf->d_zistepu;

				newzibottom = newzi * 0.99;

				testzi = surf2->d_ziorigin + fv*surf2->d_zistepv +

						fu*surf2->d_zistepu;

				if (newzibottom >= testzi)

				{

					goto newtop;

				}

				newzitop = newzi * 1.01;

				if (newzitop >= testzi)

				{

					if (surf->d_zistepu >= surf2->d_zistepu)

					{

						goto newtop;

					}

				}

			}

continue_search:

			do

			{

				surf2 = surf2->next;

			} while (surf->key > surf2->key);

			if (surf->key == surf2->key)

			{

			// if it's two surfaces on the same plane, the one that's already

			// active is in front, so keep going unless it's a bmodel

				if (!surf->insubmodel)

					goto continue_search;

			// must be two bmodels in the same leaf; sort on 1/z

				fu = (float)(edge->u - 0xFFFFF) * (1.0 / 0x100000);

				newzi = surf->d_ziorigin + fv*surf->d_zistepv +

						fu*surf->d_zistepu;

				newzibottom = newzi * 0.99;

				testzi = surf2->d_ziorigin + fv*surf2->d_zistepv +

						fu*surf2->d_zistepu;

				if (newzibottom >= testzi)

				{

					goto gotposition;

				}

				newzitop = newzi * 1.01;

				if (newzitop >= testzi)

				{

					if (surf->d_zistepu >= surf2->d_zistepu)

					{

						goto gotposition;

					}

				}

				goto continue_search;

			}

			goto gotposition;

newtop:

		// emit a span (obscures current top)

			iu = edge->u >> 20;

			if (iu > surf2->last_u)

			{

				span = span_p++;

				span->u = surf2->last_u;

				span->count = iu - span->u;

				span->v = current_iv;

				span->pnext = surf2->spans;

				surf2->spans = span;

			}

			// set last_u on the new span

			surf->last_u = iu;

gotposition:

		// insert before surf2

			surf->next = surf2;

			surf->prev = surf2->prev;

			surf2->prev->next = surf;

			surf2->prev = surf;

		}

	}

}

/*

==============

R_GenerateSpans

==============

*/

void R_GenerateSpans (void)

{

	edge_t			*edge;

	surf_t			*surf;

	r_bmodelactive = 0;

// clear active surfaces to just the background surface

	surfaces[1].next = surfaces[1].prev = &surfaces[1];

	surfaces[1].last_u = edge_head_u_shift20;

// generate spans

	for (edge=edge_head.next ; edge != &edge_tail; edge=edge->next)

	{

		if (edge->surfs[0])

		{

		// it has a left surface, so a surface is going away for this span

			surf = &surfaces[edge->surfs[0]];

			R_TrailingEdge (surf, edge);

			if (!edge->surfs[1])

				continue;

		}

		R_LeadingEdge (edge);

	}

	R_CleanupSpan ();

}

#endif	// !id386

/*

==============

R_GenerateSpansBackward

==============

*/

void R_GenerateSpansBackward (void)

{

	edge_t			*edge;

	r_bmodelactive = 0;

// clear active surfaces to just the background surface

	surfaces[1].next = surfaces[1].prev = &surfaces[1];

	surfaces[1].last_u = edge_head_u_shift20;

// generate spans

	for (edge=edge_head.next ; edge != &edge_tail; edge=edge->next)

	{

		if (edge->surfs[0])

			R_TrailingEdge (&surfaces[edge->surfs[0]], edge);

		if (edge->surfs[1])

			R_LeadingEdgeBackwards (edge);

	}

	R_CleanupSpan ();

}

/*

==============

R_ScanEdges

Input:

newedges[] array

	this has links to edges, which have links to surfaces

Output:

Each surface has a linked list of its visible spans

==============

*/

void R_ScanEdges (void)

{

	int		iv, bottom;

	byte	basespans[MAXSPANS*sizeof(espan_t)+CACHE_SIZE];

	espan_t	*basespan_p;

	surf_t	*s;

	basespan_p = (espan_t *)

			((long)(basespans + CACHE_SIZE - 1) & ~(CACHE_SIZE - 1));

	max_span_p = &basespan_p[MAXSPANS - r_refdef.vrect.width];

	span_p = basespan_p;

// clear active edges to just the background edges around the whole screen

// FIXME: most of this only needs to be set up once

	edge_head.u = r_refdef.vrect.x << 20;

	edge_head_u_shift20 = edge_head.u >> 20;

	edge_head.u_step = 0;

	edge_head.prev = NULL;

	edge_head.next = &edge_tail;

	edge_head.surfs[0] = 0;

	edge_head.surfs[1] = 1;

	edge_tail.u = (r_refdef.vrectright << 20) + 0xFFFFF;

	edge_tail_u_shift20 = edge_tail.u >> 20;

	edge_tail.u_step = 0;

	edge_tail.prev = &edge_head;

	edge_tail.next = &edge_aftertail;

	edge_tail.surfs[0] = 1;

	edge_tail.surfs[1] = 0;

	edge_aftertail.u = -1;		// force a move

	edge_aftertail.u_step = 0;

	edge_aftertail.next = &edge_sentinel;

	edge_aftertail.prev = &edge_tail;

// FIXME: do we need this now that we clamp x in r_draw.c?

	edge_sentinel.u = 2000 << 24;		// make sure nothing sorts past this

	edge_sentinel.prev = &edge_aftertail;

//

// process all scan lines

//

	bottom = r_refdef.vrectbottom - 1;

	for (iv=r_refdef.vrect.y ; iv

	{

		current_iv = iv;

		fv = (float)iv;

	// mark that the head (background start) span is pre-included

		surfaces[1].spanstate = 1;

		if (newedges[iv])

		{

			R_InsertNewEdges (newedges[iv], edge_head.next);

		}

		(*pdrawfunc) ();

	// flush the span list if we can't be sure we have enough spans left for

	// the next scan

		if (span_p >= max_span_p)

		{

			VID_UnlockBuffer ();

			S_ExtraUpdate ();	// don't let sound get messed up if going slow

			VID_LockBuffer ();

			if (r_drawculledpolys)

			{

				R_DrawCulledPolys ();

			}

			else

			{

				D_DrawSurfaces ();

			}

		// clear the surface span pointers

			for (s = &surfaces[1] ; s

				s->spans = NULL;

			span_p = basespan_p;

		}

		if (removeedges[iv])

			R_RemoveEdges (removeedges[iv]);

		if (edge_head.next != &edge_tail)

			R_StepActiveU (edge_head.next);

	}

// do the last scan (no need to step or sort or remove on the last scan)

	current_iv = iv;

	fv = (float)iv;

// mark that the head (background start) span is pre-included

	surfaces[1].spanstate = 1;

	if (newedges[iv])

		R_InsertNewEdges (newedges[iv], edge_head.next);

	(*pdrawfunc) ();

// draw whatever's left in the span list

	if (r_drawculledpolys)

		R_DrawCulledPolys ();

	else

		D_DrawSurfaces ();

}