r_edge.c

#include "quakedef.h"

/* 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?
*/

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];

static espan_t *span_p, *max_span_p;

int		r_currentkey;

extern	int	screenwidth;

static int current_iv, edge_head_u_shift20, edge_tail_u_shift20;
static edge_t edge_head, edge_tail, edge_aftertail, edge_sentinel;
static float fv;

static void (*pdrawfunc)(void);

void R_GenerateSpans (void);

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

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

/*
==============
R_BeginEdgeFrame
==============
*/
void R_BeginEdgeFrame (void)
{
	r_edges = Arr_AllocExtra(r_edges, &r_numallocatededges, r_outofedges);
	edge_p = r_edges;
	edge_max = &r_edges[r_numallocatededges];
	r_outofedges = 0;

	surfaces = Arr_AllocExtra(surfaces, &r_cnumsurfs, r_outofsurfaces);
	surf_max = &surfaces[r_cnumsurfs];
	r_outofsurfaces = 0;

	surface_p = &surfaces[2];	// background is surface 1,
								//  surface 0 is a dummy
	surfaces[1].spans = nil;	// no background spans yet
	surfaces[1].flags = SURF_DRAWBACKGROUND;

	// put the background behind everything in the world
	pdrawfunc = R_GenerateSpans;
	surfaces[1].key = 0x7FFFFFFF;
	r_currentkey = 0;

	memset(newedges, 0, sizeof(newedges));
	memset(removeedges, 0, sizeof(removeedges));
}


/*
==============
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) != nil);
}


/*
==============
R_RemoveEdges
==============
*/
void R_RemoveEdges (edge_t *pedge)
{
	do
	{
		pedge->next->prev = pedge->prev;
		pedge->prev->next = pedge->next;
	} while ((pedge = pedge->nextremove) != nil);
}


/*
==============
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;
	}
}


/*
==============
R_CleanupSpan
==============
*/
void R_CleanupSpan (void)
{
	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_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 == 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;
	}
}


/*
==============
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)
		{
			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;

	// 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 ();
}

/*
==============
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;
	espan_t	*basespan_p;
	surf_t	*s;

	r_basespans = Arr_AllocExtra(r_basespans, &r_numallocatedbasespans, r_outofspans);
	basespan_p = (espan_t *)r_basespans;
	assert(r_numallocatedbasespans > r_refdef.vrect.width);
	max_span_p = &basespan_p[r_numallocatedbasespans - r_refdef.vrect.width];
	span_p = basespan_p;
	r_outofspans = 0;

	// 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 = nil;
	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 = 0x7d << 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<bottom ; 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)
		{
			r_outofspans++;
			D_DrawSurfaces ();

			// clear the surface span pointers
			for (s = &surfaces[1] ; s<surface_p ; s++)
				s->spans = nil;

			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
	D_DrawSurfaces ();
}