/*
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.

*/
// gl_mesh.c: triangle model functions

#include "quakedef.h"

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

ALIAS MODEL DISPLAY LIST GENERATION

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

model_t		*aliasmodel;
aliashdr_t	*paliashdr;

qboolean	used[8192];

// the command list holds counts and s/t values that are valid for
// every frame
int		commands[8192];
int		numcommands;

// all frames will have their vertexes rearranged and expanded
// so they are in the order expected by the command list
int		vertexorder[8192];
int		numorder;

int		allverts, alltris;

int		stripverts[128];
int		striptris[128];
int		stripcount;

/*
================
StripLength
================
*/
int StripLength (int starttri, int startv)
{
	int		m1, m2, j, k;
	mtriangle_t	*last, *check;

	used[starttri] = 2;

	last = &triangles[starttri];

	stripverts[0] = last->vertindex[(startv+0)%3];
	stripverts[1] = last->vertindex[(startv+1)%3];
	stripverts[2] = last->vertindex[(startv+2)%3];

	striptris[0] = starttri;
	stripcount = 1;

	m1 = last->vertindex[(startv+2)%3];
	m2 = last->vertindex[(startv+1)%3];

	// look for a matching triangle
nexttri:
	for (j = starttri + 1, check = &triangles[starttri+1] ; j < pheader->numtris ; j++, check++)
	{
		if (check->facesfront != last->facesfront)
			continue;

		for (k = 0 ; k < 3 ; k++)
		{
			if (check->vertindex[k] != m1 || check->vertindex[(k+1)%3] != m2)
				continue;

			// this is the next part of the fan

			// if we can't use this triangle, this tristrip is done
			if (used[j])
				goto done;

			// the new edge
			if (stripcount & 1)
				m2 = check->vertindex[(k+2)%3];
			else
				m1 = check->vertindex[(k+2)%3];

			stripverts[stripcount+2] = check->vertindex[(k+2)%3];
			striptris[stripcount] = j;
			stripcount++;

			used[j] = 2;
			goto nexttri;
		}
	}

done:
	// clear the temp used flags
	for (j = starttri + 1 ; j < pheader->numtris ; j++)
		if (used[j] == 2)
			used[j] = 0;

	return stripcount;
}

/*
===========
FanLength
===========
*/
int FanLength (int starttri, int startv)
{
	int		m1, m2, j, k;
	mtriangle_t	*last, *check;

	used[starttri] = 2;

	last = &triangles[starttri];

	stripverts[0] = last->vertindex[(startv+0)%3];
	stripverts[1] = last->vertindex[(startv+1)%3];
	stripverts[2] = last->vertindex[(startv+2)%3];

	striptris[0] = starttri;
	stripcount = 1;

	m1 = last->vertindex[(startv+0)%3];
	m2 = last->vertindex[(startv+2)%3];

	// look for a matching triangle
nexttri:
	for (j = starttri + 1, check = &triangles[starttri+1] ; j < pheader->numtris ; j++, check++)
	{
		if (check->facesfront != last->facesfront)
			continue;

		for (k = 0 ; k < 3 ; k++)
		{
			if (check->vertindex[k] != m1 || check->vertindex[(k+1)%3] != m2)
				continue;

			// this is the next part of the fan

			// if we can't use this triangle, this tristrip is done
			if (used[j])
				goto done;

			// the new edge
			m2 = check->vertindex[(k+2)%3];

			stripverts[stripcount+2] = m2;
			striptris[stripcount] = j;
			stripcount++;

			used[j] = 2;
			goto nexttri;
		}
	}

done:
	// clear the temp used flags
	for (j = starttri + 1 ; j < pheader->numtris ; j++)
		if (used[j] == 2)
			used[j] = 0;

	return stripcount;
}

/*
================
BuildTris

Generate a list of trifans or strips for the model, which holds for all frames
================
*/
void BuildTris (void)
{
	int		i, j, k, startv, len, bestlen, besttype, type, bestverts[1024], besttris[1024];
	float	s, t;

	// build tristrips
	numorder = 0;
	numcommands = 0;
	memset (used, 0, sizeof(used));
	for (i = 0 ; i < pheader->numtris ; i++)
	{
		// pick an unused triangle and start the trifan
		if (used[i])
			continue;

		bestlen = 0;
		for (type = 0 ; type < 2 ; type++)
//	type = 1;
		{
			for (startv = 0 ; startv < 3 ; startv++)
			{
				len = (type == 1) ? StripLength (i, startv) : FanLength (i, startv);
				if (len > bestlen)
				{
					besttype = type;
					bestlen = len;
					for (j = 0 ; j < bestlen + 2 ; j++)
						bestverts[j] = stripverts[j];
					for (j = 0 ; j < bestlen ; j++)
						besttris[j] = striptris[j];
				}
			}
		}

		// mark the tris on the best strip as used
		for (j = 0 ; j < bestlen ; j++)
			used[besttris[j]] = 1;

		commands[numcommands++] = (besttype == 1) ? (bestlen + 2) : -(bestlen + 2);

		for (j = 0 ; j < bestlen + 2 ; j++)
		{
			// emit a vertex into the reorder buffer
			k = bestverts[j];
			vertexorder[numorder++] = k;

			// emit s/t coords into the commands stream
			s = stverts[k].s;
			t = stverts[k].t;
			if (!triangles[besttris[0]].facesfront && stverts[k].onseam)
				s += pheader->skinwidth / 2;	// on back side
			s = (s + 0.5) / pheader->skinwidth;
			t = (t + 0.5) / pheader->skinheight;

			*(float *)&commands[numcommands++] = s;
			*(float *)&commands[numcommands++] = t;
		}
	}

	commands[numcommands++] = 0;		// end of list marker

	Con_DPrintf ("%3i tri %3i vert %3i cmd\n", pheader->numtris, numorder, numcommands);

	allverts += numorder;
	alltris += pheader->numtris;
}

void ScaleVerts (byte *original, vec3_t scaled)
{
	scaled[0] = (float)original[0] * paliashdr->scale[0] + paliashdr->scale_origin[0];
	scaled[1] = (float)original[1] * paliashdr->scale[1] + paliashdr->scale_origin[1];
	scaled[2] = (float)original[2] * paliashdr->scale[2] + paliashdr->scale_origin[2];
}

/*
================
GL_MakeAliasModelDisplayLists
================
*/
void GL_MakeAliasModelDisplayLists (model_t *m, aliashdr_t *hdr)
{
	int			i, j, *cmds;
	trivertx_t	*verts;

	aliasmodel = m;
	paliashdr = hdr;	// (aliashdr_t *)Mod_Extradata (m);

	// Tonik: don't cache anything, because it seems just as fast
	// (if not faster) to rebuild the tris instead of loading them from disk
	BuildTris ();		// trifans or lists

	// save the data out
	paliashdr->poseverts = numorder;

	cmds = Hunk_Alloc (numcommands * 4);
	paliashdr->commands = (byte *)cmds - (byte *)paliashdr;
	memcpy (cmds, commands, numcommands * 4);

	verts = Hunk_Alloc (paliashdr->numposes * paliashdr->poseverts * sizeof(trivertx_t));
	paliashdr->posedata = (byte *)verts - (byte *)paliashdr;
	for (i = 0 ; i < paliashdr->numposes ; i++)
		for (j = 0 ; j < numorder ; j++)
			*verts++ = poseverts[i][vertexorder[j]];

	// code for elimination of muzzleflashes on viewmodels
	if (m->modhint == MOD_WEAPON && qmb_initialized && gl_part_muzzleflash.value)
	{
		vec3_t	scaledf0, scaledf1;	// scaled versions of the verts (need to prescale for comparison)
		float	vdiff;				// difference in front to back movement
		qboolean *nodraw;			// true if the vert is a muzzleflash

		// get pointers to the verts
		trivertx_t	*vertsf0 = (trivertx_t *)((byte *)hdr + hdr->posedata);
		trivertx_t	*vertsfi = (trivertx_t *)((byte *)hdr + hdr->posedata);

		// set up the nodraw buffer
		nodraw = Q_malloc (numorder * sizeof(qboolean));

		// setthese pointers to the 0th and 1st frames
		vertsf0 += hdr->frames[0].firstpose * hdr->poseverts;
		vertsfi += hdr->frames[1].firstpose * hdr->poseverts;

		// now go through them and compare.  we expect that (a) the animation is sensible and there's no major
		// difference between the 2 frames to be expected, and (b) any verts that do exhibit a major difference
		// can be assumed to belong to the muzzleflash
		for (j = 0; j < numorder; j++)
		{
			ScaleVerts (vertsf0->v, scaledf0);
			ScaleVerts (vertsfi->v, scaledf1);

			// get difference in front to back movement
			vdiff = scaledf1[0] - scaledf0[0];

			// if it's above a certain treshold, assume a muzzleflash and mark for nodraw
			// 10 is the approx lowest range of visible front to back in a view model, so that seems reasonable to work with
			if (vdiff > 10)
				nodraw[j] = true;
			else nodraw[j] = false;

			// next set of verts
			vertsf0++;
			vertsfi++;
		}

		// copy the relevant verts from the first frame to every other frame
		for (i = 1; i < paliashdr->numframes; i++)
		{
			// get pointers to the verts again
			vertsf0 = (trivertx_t *)((byte *) hdr + hdr->posedata);
			vertsfi = (trivertx_t *)((byte *) hdr + hdr->posedata);

			// set these pointers to the 0th and i'th frames
			vertsf0 += hdr->frames[0].firstpose * hdr->poseverts;
			vertsfi += hdr->frames[i].firstpose * hdr->poseverts;

			for (j = 0; j < numorder; j++)
			{
				// copy the verts from frame 0
				if (nodraw[j])
				{
					vertsfi->v[0] = vertsf0->v[0];
					vertsfi->v[1] = vertsf0->v[1];
					vertsfi->v[2] = vertsf0->v[2];
				}

				// next set of verts
				vertsf0++;
				vertsfi++;
			}
		}

		// release the nodraw buffer
		free (nodraw);
	}
}
