fs2open.github.com/code/weapon/trails.cpp

/*
 * Copyright (C) Volition, Inc. 1999.  All rights reserved.
 *
 * All source code herein is the property of Volition, Inc. You may not sell 
 * or otherwise commercially exploit the source or things you created based on the 
 * source.
 *
*/

/*
 * $Logfile: /Freespace2/code/Weapon/Trails.cpp $
 * $Revision: 2.16 $
 * $Date: 2004-03-05 09:01:54 $
 * $Author: Goober5000 $
 *
 * Code for missile trails
 *
 * $Log: not supported by cvs2svn $
 * Revision 2.15  2004/02/20 04:29:57  bobboau
 * pluged memory leaks,
 * 3D HTL lasers (they work perfictly)
 * and posably fixed Turnsky's shinemap bug
 *
 * Revision 2.14  2004/02/16 11:47:34  randomtiger
 * Removed a lot of files that we dont need anymore.
 * Changed htl to be on by default, command now -nohtl
 * Changed D3D to use a 2D vertex for 2D operations which should cut down on redundant data having to go though the system.
 * Added small change to all -start_mission flag to take you to any mission by filename, very useful for testing.
 * Removed old dshow code and took away timerbar compile flag condition since it uses a runtime flag now.
 *
 * Revision 2.13  2004/02/14 00:18:37  randomtiger
 * Please note that from now on OGL will only run with a registry set by Launcher v4. See forum for details.
 * OK, these changes effect a lot of file, I suggest everyone updates ASAP:
 * Removal of many files from project.
 * Removal of meanless Gr_bitmap_poly variable.
 * Removal of glide, directdraw, software modules all links to them, and all code specific to those paths.
 * Removal of redundant Fred paths that arent needed for Fred OGL.
 * Have seriously tidied the graphics initialisation code and added generic non standard mode functionality.
 * Fixed many D3D non standard mode bugs and brought OGL up to the same level.
 * Removed texture section support for D3D8, voodoo 2 and 3 cards will no longer run under fs2_open in D3D, same goes for any card with a maximum texture size less than 1024.
 *
 * Revision 2.12  2004/02/04 09:02:42  Goober5000
 * got rid of unnecessary double semicolons
 * --Goober5000
 *
 * Revision 2.11  2003/11/19 20:37:25  randomtiger
 * Almost fully working 32 bit pcx, use -pcx32 flag to activate.
 * Made some commandline variables fit the naming standard.
 * Changed timerbar system not to run pushes and pops if its not in use.
 * Put in a note about not uncommenting asserts.
 * Fixed up a lot of missing POP's on early returns?
 * Perhaps the motivation for Assert functionality getting commented out?
 * Fixed up some bad asserts.
 * Changed nebula poofs to render in 2D in htl, it makes it look how it used to in non htl. (neb.cpp,1248)
 * Before the poofs were creating a nasty stripe effect where they intersected with ships hulls.
 * Put in a special check for the signs of that D3D init bug I need to lock down.
 *
 * Revision 2.10  2003/11/17 04:25:58  bobboau
 * made the poly list dynamicly alocated,
 * started work on fixing the node model not rendering,
 * but most of that got commented out so I wouldn't have to deal with it
 * while mucking about with the polylist
 *
 * Revision 2.9  2003/11/16 04:09:20  Goober5000
 * language
 *
 * Revision 2.8  2003/11/11 03:56:13  bobboau
 * lots of bug fixing, much of it in nebula and bitmap drawing
 *
 * Revision 2.7  2003/11/09 06:31:40  Kazan
 * a couple of htl functions being called in nonhtl (ie NULL functions) problems fixed
 * conflicts in cmdline and timerbar.h log entries
 * cvs stopped acting like it was on crack obviously
 *
 * Revision 2.6  2003/11/02 05:50:08  bobboau
 * modified trails to render with tristrips now rather than with stinky old trifans,
 * MUCH faster now, at least one order of magnatude.
 *
 * Revision 2.5  2003/10/23 18:03:25  randomtiger
 * Bobs changes (take 2)
 *
 * Revision 2.4  2003/08/21 15:04:17  phreak
 * zeroed out the specular fields since they caused some flickering
 *
 * Revision 2.3  2003/07/15 16:07:12  phreak
 * trails now properly alphablend in ogl as it does in d3d
 *
 * Revision 2.2  2003/05/04 20:50:06  phreak
 * bumped MAX_TRAILS to 500 because of afterburner trails
 *
 * Revision 2.1  2002/08/01 01:41:11  penguin
 * The big include file move
 *
 * Revision 2.0  2002/06/03 04:02:29  penguin
 * Warpcore CVS sync
 *
 * Revision 1.2  2002/05/04 04:52:22  mharris
 * 1st draft at porting
 *
 * Revision 1.1  2002/05/02 18:03:13  mharris
 * Initial checkin - converted filenames and includes to lower case
 *
 * 
 * 7     6/23/99 2:23p Mattk
 * Fixed detail level trail rendering problem.
 * 
 * 6     6/22/99 7:03p Dave
 * New detail options screen.
 * 
 * 5     2/23/99 8:11p Dave
 * Tidied up dogfight mode. Fixed TvT ship type problems for alpha wing.
 * Small pass over todolist items.
 * 
 * 4     2/17/99 2:11p Dave
 * First full run of squad war. All freespace and tracker side stuff
 * works.
 * 
 * 3     11/14/98 5:33p Dave
 * Lots of nebula work. Put in ship contrails.
 * 
 * 2     10/07/98 10:54a Dave
 * Initial checkin.
 * 
 * 1     10/07/98 10:51a Dave
 * 
 * 9     5/13/98 3:10p John
 * made detail slider for weapon rendering change the distance that lasers
 * become non-textured.  The lowest setting turns off missile trail
 * rendering.
 * 
 * 8     5/08/98 7:09p Dave
 * Lots of UI tweaking.
 * 
 * 7     4/10/98 5:20p John
 * Changed RGB in lighting structure to be ubytes.  Removed old
 * not-necessary 24 bpp software stuff.
 * 
 * 6     3/31/98 5:19p John
 * Removed demo/save/restore.  Made NDEBUG defined compile.  Removed a
 * bunch of debug stuff out of player file.  Made model code be able to
 * unload models and malloc out only however many models are needed.
 *  
 * 
 * 5     3/23/98 5:00p John
 * Improved missile trails.  Made smooth alpha under hardware.  Made end
 * taper.  Made trail touch weapon.
 * 
 * 4     1/23/98 5:08p John
 * Took L out of vertex structure used B (blue) instead.   Took all small
 * fireballs out of fireball types and used particles instead.  Fixed some
 * debris explosion things.  Restructured fireball code.   Restructured
 * some lighting code.   Made dynamic lighting on by default. Made groups
 * of lasers only cast one light.  Made fireballs not cast light.
 * 
 * 3     1/15/98 11:13a John
 * Added code for specifying weapon trail bitmaps in weapons.tbl
 * 
 * 2     12/21/97 6:15p John
 * Made a seperate system for missile trails
 * 
 * 1     12/21/97 5:30p John
 * Initial version
 *
 * $NoKeywords: $
 */

#include "weapon/trails.h"
#include "globalincs/systemvars.h"
#include "globalincs/linklist.h"
#include "render/3d.h" 
#include "io/timer.h"
#include "ship/ship.h"

#define MAX_TRAILS 500

// Stuff for missile trails doesn't need to be saved or restored... or does it?
typedef struct trail {
	int		head, tail;						// pointers into the queue for the trail points
	vector	pos[NUM_TRAIL_SECTIONS];	// positions of trail points
	float		val[NUM_TRAIL_SECTIONS];	// for each point, a value that tells how much to fade out	
	int		object_died;					// set to zero as long as object	
	int		trail_stamp;					// trail timestamp	

	// trail info
	trail_info info;							// this is passed when creating a trail

	struct	trail * prev;
	struct	trail * next;
} trail;


int Num_trails = 0;
trail Trails[MAX_TRAILS];

trail Trail_free_list;
trail Trail_used_list;

// Reset everything between levels
void trail_level_init()
{
	int i;

	Num_trails = 0;
	list_init( &Trail_free_list );
	list_init( &Trail_used_list );

	// Link all object slots into the free list
	for (i=0; i<MAX_TRAILS; i++)	{
		list_append(&Trail_free_list, &Trails[i] );
	}
}

//returns the number of a free trail
//returns -1 if no free trails
int trail_create(trail_info info)
{
	int trail_num;
	trail *trailp;

	// standalone server should never create trails
	if(Game_mode & GM_STANDALONE_SERVER){
		return -1;
	}

	if ( !Detail.weapon_extras )	{
		// No trails at slot 0
		return -1;
	}

	if (Num_trails >= MAX_TRAILS ) {
		#ifndef NDEBUG
		mprintf(("Trail creation failed - too many trails!\n" ));
		#endif
		return -1;
	}

	// Find next available trail
	trailp = GET_FIRST(&Trail_free_list);
	Assert( trailp != &Trail_free_list );		// shouldn't have the dummy element

	// remove trailp from the free list
	list_remove( &Trail_free_list, trailp );
	
	// insert trailp onto the end of used list
	list_append( &Trail_used_list, trailp );

	// increment counter
	Num_trails++;

	// get objnum
	trail_num = trailp-Trails;

	// Init the trail data
	trailp->info = info;
	trailp->tail = 0;
	trailp->head = 0;	
	trailp->object_died = 0;		
	trailp->trail_stamp = timestamp(trailp->info.stamp);

	return trail_num;
}

// output top and bottom vectors
// fvec == forward vector (eye viewpoint basically. in world coords)
// pos == world coordinate of the point we're calculating "around"
// w == width of the diff between top and bottom around pos
void trail_calc_facing_pts( vector *top, vector *bot, vector *fvec, vector *pos, float w )
{
	vector uvec, rvec;

	vm_vec_sub( &rvec, &Eye_position, pos );
	vm_vec_normalize( &rvec );

	vm_vec_crossprod(&uvec,fvec,&rvec);
	vm_vec_normalize(&uvec);

	vm_vec_scale_add( top, pos, &uvec, w/2.0f );
	vm_vec_scale_add( bot, pos, &uvec, -w/2.0f );
}

// trail is on ship
int trail_is_on_ship(int trail_index, ship *shipp)
{
	int idx;

	for(idx=0; idx<MAX_SHIP_CONTRAILS; idx++){
		if(shipp->trail_num[idx] == (short)trail_index){
			return 1;
		}
	}

	// nope
	return 0;
}

extern int OGL_inited;

// Render the trail behind a missile.
// Basically a queue of points that face the viewer
extern int Cmdline_nohtl;
/*
void trail_render( trail * trailp )
{
	trail_info *ti;	

	if ( trailp->tail == trailp->head ) return;

	ti = &trailp->info;	

	vector topv, botv, *fvec, last_pos, tmp_fvec;
	vertex last_top, last_bot, top, bot;

	int sections[NUM_TRAIL_SECTIONS];
	int num_sections = 0;

	int n = trailp->tail;

	// if this trail is on the player ship, and he's in any padlock view except rear view, don't draw	
	if((Player_ship != NULL) && trail_is_on_ship(trailp - Trails, Player_ship) && (Viewer_mode & (VM_PADLOCK_UP | VM_PADLOCK_LEFT | VM_PADLOCK_RIGHT)) ){
		return;
	}

	do	{
		n--;
		if ( n < 0 ) n = NUM_TRAIL_SECTIONS-1;


		if ( trailp->val[n] > 1.0f ) {
			break;
		}

		sections[num_sections++] = n;

	} while ( n != trailp->head );

	int i;

	for (i=0; i<num_sections; i++ )	{

		n = sections[i];

		float w;
		ubyte l;

		w = trailp->val[n]*(ti->w_end - ti->w_start) + ti->w_start;
		l = (ubyte)fl2i((trailp->val[n]*(ti->a_end - ti->a_start) + ti->a_start)*255.0f);

		vector pos;

		pos = trailp->pos[n];

		if ( i == 0 )	{
			//fvec = 
			//&objp->orient.fvec;
			if ( num_sections > 1 )	{
	
				vm_vec_sub(&tmp_fvec, &pos, &trailp->pos[sections[i+1]] );
				vm_vec_normalize_safe(&tmp_fvec);
				fvec = &tmp_fvec;

			} else {
				fvec = &tmp_fvec;
				fvec->xyz.x = 0.0f;
				fvec->xyz.y = 0.0f;
				fvec->xyz.z = 1.0f;
			}
		} else {
			vm_vec_sub(&tmp_fvec, &last_pos, &pos );
			vm_vec_normalize_safe(&tmp_fvec);
			fvec = &tmp_fvec;
		}
			
		trail_calc_facing_pts( &topv, &botv, fvec, &pos, w );
	
		if(!Cmdline_nohtl){
			g3_transfer_vertex( &top, &topv );
			g3_transfer_vertex( &bot, &botv );
		}else{
			g3_rotate_vertex( &top, &topv );
			g3_rotate_vertex( &bot, &botv );
		}
		top.a = bot.a = l;	

		if ( i > 0 )	{

			if ( i == num_sections-1 )	{
				// Last one...
				vector centerv;
				vm_vec_avg( &centerv, &topv, &botv );
				vertex center;
				if(!Cmdline_nohtl){
					g3_transfer_vertex( &center, &centerv );
				}else{
					g3_rotate_vertex( &center, &centerv );
				}
				center.a = l;	

				vertex *vlist[3];
				vlist[0] = &last_top;
				vlist[1] = &last_bot;
				vlist[2] = &center;

				vlist[0]->u = 0.0f;  vlist[0]->v = 1.0f; vlist[0]->spec_r=vlist[0]->spec_g=vlist[0]->spec_b=0;
				vlist[1]->u = 0.0f;  vlist[1]->v = 0.0f; vlist[1]->spec_r=vlist[1]->spec_g=vlist[1]->spec_b=0;
				vlist[2]->u = 1.0f;  vlist[2]->v = 0.5f; vlist[1]->spec_r=vlist[1]->spec_g=vlist[1]->spec_b=0;

				gr_set_bitmap(ti->bitmap, GR_ALPHABLEND_FILTER, GR_BITBLT_MODE_NORMAL, l/255.0f );

					if(Cmdline_nohtl)g3_draw_poly( 3, vlist, TMAP_FLAG_TEXTURED|TMAP_FLAG_ALPHA|TMAP_FLAG_GOURAUD );
					else g3_draw_poly( 3, vlist, TMAP_FLAG_TEXTURED|TMAP_FLAG_ALPHA|TMAP_FLAG_GOURAUD | TMAP_FLAG_TEXTURED | TMAP_HTL_3D_UNLIT );

			} else {
				vertex *vlist[4];
				vlist[0] = &last_bot;
				vlist[1] = &bot;
				vlist[2] = &top;
				vlist[3] = &last_top;

				vlist[0]->u = 0.0f;  vlist[0]->v = 0.0f; vlist[0]->spec_r=vlist[0]->spec_g=vlist[0]->spec_b=0;
				vlist[1]->u = 1.0f;  vlist[1]->v = 0.0f; vlist[1]->spec_r=vlist[1]->spec_g=vlist[1]->spec_b=0;
				vlist[2]->u = 1.0f;  vlist[2]->v = 1.0f; vlist[2]->spec_r=vlist[2]->spec_g=vlist[2]->spec_b=0;
				vlist[3]->u = 0.0f;  vlist[3]->v = 1.0f; vlist[3]->spec_r=vlist[3]->spec_g=vlist[3]->spec_b=0;

				gr_set_bitmap(ti->bitmap, GR_ALPHABLEND_FILTER, GR_BITBLT_MODE_NORMAL, l/255.0f );
					if(Cmdline_nohtl)g3_draw_poly( 4, vlist, TMAP_FLAG_TEXTURED|TMAP_FLAG_ALPHA|TMAP_FLAG_GOURAUD );
					else g3_draw_poly( 4, vlist, TMAP_FLAG_TEXTURED|TMAP_FLAG_ALPHA|TMAP_FLAG_GOURAUD | TMAP_FLAG_TEXTURED | TMAP_HTL_3D_UNLIT );
			}
		}
		last_pos = pos;
		last_top = top;
		last_bot = bot;
	}
}
*/
#define MAX_TRAIL_POLYS 129
void trail_render( trail * trailp )
{		
//	if(!Cmdline_nohtl)gr_set_lighting(false,false);//this shouldn't need to be here but it does need to be here, WHY!!!!!!!?-Bobboau
	trail_info *ti;	

	if ( trailp->tail == trailp->head ) 
	{
		return;
	}

	ti = &trailp->info;	

	vector topv, botv, *fvec, last_pos, tmp_fvec;
	vertex  top, bot;

	int sections[NUM_TRAIL_SECTIONS];
	int num_sections = 0;

	int n = trailp->tail;

	// if this trail is on the player ship, and he's in any padlock view except rear view, don't draw	
	if((Player_ship != NULL) && trail_is_on_ship(trailp - Trails, Player_ship) && (Viewer_mode & (VM_PADLOCK_UP | VM_PADLOCK_LEFT | VM_PADLOCK_RIGHT)) ){
		return;
	}

	do	{
		n--;
		if ( n < 0 ) n = NUM_TRAIL_SECTIONS-1;


		if ( trailp->val[n] > 1.0f ) {
			break;
		}

		sections[num_sections++] = n;

	} while ( n != trailp->head );

	int i;

	vertex *vlist[MAX_TRAIL_POLYS];
	vertex v_list[MAX_TRAIL_POLYS];
	int nv = 0;

	for (i=0; i<num_sections; i++ )	{

	if(nv>MAX_TRAIL_POLYS-3)Error( LOCATION, "too many verts in trail render\n" );

		n = sections[i];

		float w;
		ubyte l;

		w = trailp->val[n]*(ti->w_end - ti->w_start) + ti->w_start;
		l = (ubyte)fl2i((trailp->val[n]*(ti->a_end - ti->a_start) + ti->a_start)*255.0f);

		vector pos;

		pos = trailp->pos[n];

		if ( i == 0 )	{
			//fvec = 
			//&objp->orient.fvec;
			if ( num_sections > 1 )	{
	
				vm_vec_sub(&tmp_fvec, &pos, &trailp->pos[sections[i+1]] );
				vm_vec_normalize_safe(&tmp_fvec);
				fvec = &tmp_fvec;

			} else {
				fvec = &tmp_fvec;
				fvec->xyz.x = 0.0f;
				fvec->xyz.y = 0.0f;
				fvec->xyz.z = 1.0f;
			}
		} else {
			vm_vec_sub(&tmp_fvec, &last_pos, &pos );
			vm_vec_normalize_safe(&tmp_fvec);
			fvec = &tmp_fvec;
		}
			
		trail_calc_facing_pts( &topv, &botv, fvec, &pos, w );
	
		if(!Cmdline_nohtl){
			g3_transfer_vertex( &top, &topv );
			g3_transfer_vertex( &bot, &botv );
		}else{
			g3_rotate_vertex( &top, &topv );
			g3_rotate_vertex( &bot, &botv );
		}
		top.a = bot.a = l;	

		if ( i > 0 )	{

			if ( i == num_sections-1 )	{
				// Last one...
				vector centerv;
				vm_vec_avg( &centerv, &topv, &botv );
				if(!Cmdline_nohtl){
					g3_transfer_vertex( &v_list[nv+2], &centerv );
				}else{
					g3_rotate_vertex( &v_list[nv+2], &centerv );
				}
				v_list[nv].a = l;	

				vlist[nv] = &v_list[nv];
				vlist[nv]->u = float(i);  vlist[nv]->v = 1.0f; 
				vlist[nv]->r=vlist[nv]->g=vlist[nv]->b=l; vlist[nv]->spec_r=vlist[nv]->spec_g=vlist[nv]->spec_b=0;
				nv++;
				vlist[nv] = &v_list[nv];
				vlist[nv]->u = float(i);  vlist[nv]->v = 0.0f; 
				vlist[nv]->r=vlist[nv]->g=vlist[nv]->b=l; vlist[nv]->spec_r=vlist[nv]->spec_g=vlist[nv]->spec_b=0;
				nv++;
				vlist[nv] = &v_list[nv];
				vlist[nv]->u = float(i+1);  vlist[nv]->v = 0.5f; 
				vlist[nv]->r=vlist[nv]->g=vlist[nv]->b=0; vlist[nv]->spec_r=vlist[nv]->spec_g=vlist[nv]->spec_b=0;
				nv++;



			} else {

				vlist[nv] = &v_list[nv];
				vlist[nv]->u = float(i);  vlist[nv]->v = 1.0f; 
				vlist[nv]->r=vlist[nv]->g=vlist[nv]->b=l; vlist[nv]->spec_r=vlist[nv]->spec_g=vlist[nv]->spec_b=0;
				nv++;
				vlist[nv] = &v_list[nv];
				vlist[nv]->u = float(i);  vlist[nv]->v = 0.0f; 
				vlist[nv]->r=vlist[nv]->g=vlist[nv]->b=l; vlist[nv]->spec_r=vlist[nv]->spec_g=vlist[nv]->spec_b=0;
				nv++;

			}
		}


		last_pos = pos;
		v_list[nv] = top;
		v_list[nv+1] = bot;
	}
	if(!nv) {
		return;
	}
	if(nv<3)Error( LOCATION, "too few verts in trail render\n" );
	if(nv>MAX_TRAIL_POLYS-1)Error( LOCATION, "too many verts in trail render\n" );
	if(nv%2 != 1)Error( LOCATION, "even number of verts verts in trail render\n" );//there should always be three virts in the last section and 2 everyware else, therefore there should always be an odd number of verts

	gr_set_bitmap(ti->bitmap, GR_ALPHABLEND_FILTER, GR_BITBLT_MODE_NORMAL, 1.0f );
	if(Cmdline_nohtl)	g3_draw_poly( nv, vlist,  TMAP_FLAG_TEXTURED|TMAP_FLAG_ALPHA|TMAP_FLAG_GOURAUD | TMAP_FLAG_RGB | TMAP_FLAG_TRISTRIP );
	else				g3_draw_poly( nv, vlist,  TMAP_FLAG_TEXTURED|TMAP_FLAG_ALPHA|TMAP_FLAG_GOURAUD | TMAP_FLAG_RGB | TMAP_HTL_3D_UNLIT | TMAP_FLAG_TRISTRIP );
//	TIMERBAR_POP();
}



void trail_add_segment( int trail_num, vector *pos )
{
	if (trail_num < 0 ) return;
	if (trail_num >= MAX_TRAILS ) return;

	trail *trailp = &Trails[trail_num];

	int next = trailp->tail;
	trailp->tail++;
	if ( trailp->tail >= NUM_TRAIL_SECTIONS )
		trailp->tail = 0;

	if ( trailp->head == trailp->tail )	{
		// wrapped!!
		trailp->head++;
		if ( trailp->head >= NUM_TRAIL_SECTIONS )
			trailp->head = 0;
	}
	
	trailp->pos[next] = *pos;
	trailp->val[next] = 0.0f;
}		

void trail_set_segment( int trail_num, vector *pos )
{
	if (trail_num < 0 ) return;
	if (trail_num >= MAX_TRAILS ) return;

	trail *trailp = &Trails[trail_num];

	int next = trailp->tail-1;
	if ( next < 0 )	{
		next = NUM_TRAIL_SECTIONS-1;
	}
	
	trailp->pos[next] = *pos;
}

void trail_move_all(float frametime)
{
	trail *trailp;	

	trailp=GET_FIRST(&Trail_used_list);

	while ( trailp!=END_OF_LIST(&Trail_used_list) )	{

		int num_alive_segments = 0;

		if ( trailp->tail != trailp->head )	{
			int n = trailp->tail;			
			float time_delta = frametime / trailp->info.max_life;
			do	{
				n--;
				if ( n < 0 ) n = NUM_TRAIL_SECTIONS-1;

				trailp->val[n] += time_delta;

				if ( trailp->val[n] <= 1.0f ) {
					num_alive_segments++;	// Record how many still alive.
				}

			} while ( n != trailp->head );
		}		
	
		if ( trailp->object_died && (num_alive_segments < 1) )	{
			// delete it from the list!
			trail *next_one = GET_NEXT(trailp);

			// remove objp from the used list
			list_remove( &Trail_used_list, trailp);

			// add objp to the end of the free
			list_append( &Trail_free_list, trailp );

			// decrement counter
			Num_trails--;

			Assert(Num_trails >= 0);
			
			trailp = next_one;
		} else {
			trailp=GET_NEXT(trailp);
		}
	}
}

void trail_object_died( int trail_num )
{
	if (trail_num < 0 ) return;
	if (trail_num >= MAX_TRAILS ) return;

	trail *trailp = &Trails[trail_num];
	
	trailp->object_died++;
}

void trail_render_all()
{
	trail *trailp;

	if ( !Detail.weapon_extras )	{
		// No trails at slot 0
		return;
	}

	trailp=GET_FIRST(&Trail_used_list);

	while ( trailp!=END_OF_LIST(&Trail_used_list) )	{
		trail_render(trailp);
		trailp=GET_NEXT(trailp);
	}

}
int trail_stamp_elapsed(int trail_num)
{
	return timestamp_elapsed(Trails[trail_num].trail_stamp);
}

void trail_set_stamp(int trail_num)
{
	Trails[trail_num].trail_stamp = timestamp(Trails[trail_num].info.stamp);
}