r_edge.c

Quake 2 Source code for students by Theerthan You can also download from idsoftwares.com

/*
Copyright (C) 1997-2001 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 "r_local.h"

#ifndef id386
void R_SurfacePatch (void)
{
}

void R_EdgeCodeStart (void)
{
}

void R_EdgeCodeEnd (void)
{
}
#endif


#if 0
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

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;

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;

static int	miplevel;

float		scale_for_mip;
int			ubasestep, errorterm, erroradjustup, erroradjustdown;

// FIXME: should go away
extern void			R_RotateBmodel (void);
extern void			R_TransformFrustum (void);



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);


/*
===============================================================================

EDGE SCANNING

===============================================================================
*/

/*
==============
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 (sw_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<r_refdef.vrectbottom ; 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 (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_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 == 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;
	float			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
==============
*/