shield.cpp

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/*
 * 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.
 *
*/


//      Detail level effects (Detail.shield_effects)
//              0               Nothing rendered
//              1               An animating bitmap rendered per hit, not shrink-wrapped.  Lasts half time.  One per ship.
//              2               Animating bitmap per hit, not shrink-wrapped.  Lasts full time.  Unlimited.
//              3               Shrink-wrapped texture.  Lasts half-time.
//              4               Shrink-wrapped texture.  Lasts full-time.

#include "freespace2/freespace.h"
#include "mission/missionparse.h"
#include "model/model.h"
#include "network/multi.h"
#include "object/objectshield.h"
#include "render/3d.h"
#include "ship/ship.h"
#include "species_defs/species_defs.h"

int     Show_shield_mesh = 0;

//      One unit in 3d means this in the shield hit texture map.
#define SHIELD_HIT_SCALE        0.15f                   // Note, larger constant means smaller effect
#define MAX_TRIS_PER_HIT        40                                      //      Number of triangles per shield hit, maximum.
#define MAX_SHIELD_HITS 20                                      //      Maximum number of active shield hits.
#define MAX_SHIELD_TRI_BUFFER   (MAX_SHIELD_HITS*MAX_TRIS_PER_HIT) //(MAX_SHIELD_HITS*20) //    Persistent buffer of triangle comprising all active shield hits.
#define SHIELD_HIT_DURATION     (3*F1_0/4)      //      Duration, in milliseconds, of shield hit effect

#define SH_UNUSED                       -1                                      //      Indicates an unused record in Shield_hits
#define SH_TYPE_1                       1                                       //      Indicates Shield_hits record is of type 1.

#define UV_MAX                          (63.95f/64.0f)  //      max allowed value until tmapper bugs fixed, 1/24/97

float   Shield_scale = SHIELD_HIT_SCALE;

typedef struct gshield_tri {
        int                             used;                                           //      Set if this triangle is currently in use.
        int                             trinum;                                         //      a debug parameter
        fix                             creation_time;                          //      time at which created.
        shield_vertex   verts[4];                                       //      Triangles, but at lower detail level, a square.
} gshield_tri;

typedef struct shield_hit {
        int     start_time;                                                             //      start time of this object
        int     type;                                                                   //      type, probably the weapon type, to indicate the bitmap to use
        int     objnum;                                                                 //      Object index, needed to get current orientation, position.
        int     num_tris;                                                               //      Number of Shield_tris comprising this shield.
        int     tri_list[MAX_TRIS_PER_HIT];                             //      Indices into Shield_tris, triangles for this shield hit.
        ubyte rgb[3];                                                           //  rgb colors
} shield_hit;

typedef struct shield_point {
        int             objnum;                                                         //      Object that was hit.
        int             shield_tri;                                                     //      Triangle in shield mesh that took hit.
        vec3d   hit_point;                                                      //      Point in global 3-space of hit.
} shield_point;

#define MAX_SHIELD_POINTS       100
shield_point    Shield_points[MAX_SHIELD_POINTS];
int             Num_shield_points;
int             Num_multi_shield_points;                                        // used by multiplayer clients

gshield_tri     Global_tris[MAX_SHIELD_TRI_BUFFER];     //      The persistent triangles, part of shield hits.
int     Num_tris;                                                               //      Number of triangles in current shield.  Would be a local, but needed in numerous routines.

shield_hit      Shield_hits[MAX_SHIELD_HITS];

int Shield_bitmaps_loaded = 0;

//      This is a recursive function, so prototype it.
extern void create_shield_from_triangle(int trinum, matrix *orient, shield_info *shieldp, vec3d *tcp, vec3d *centerp, float radius, vec3d *rvec, vec3d *uvec);

void load_shield_hit_bitmap()
{
        size_t i;
        // Check if we've already allocated the shield effect bitmaps
        if ( Shield_bitmaps_loaded )
                return;

        Shield_bitmaps_loaded = 1;

        for (i = 0; i < Species_info.size(); i++ )      
    {
        if (Species_info[i].shield_anim.filename[0] != '\0')
        {
                    Species_info[i].shield_anim.first_frame = bm_load_animation(Species_info[i].shield_anim.filename, &Species_info[i].shield_anim.num_frames, NULL, NULL, 1);
                    Assertion((Species_info[i].shield_anim.first_frame >= 0), "Error while loading shield hit ani: %s for species: %s\n", Species_info[i].shield_anim.filename, Species_info[i].species_name);
        }
        }
}

void shield_hit_page_in()
{
        size_t i;

        if ( !Shield_bitmaps_loaded )   {
                load_shield_hit_bitmap();
        }

        for (i = 0; i < Species_info.size(); i++) {
                generic_anim *sa = &Species_info[i].shield_anim;
                if ( sa->first_frame >= 0 ) {
                        bm_page_in_xparent_texture(sa->first_frame, sa->num_frames );
                }
        }
}


void shield_hit_init()
{
        int     i;

        for (i=0; i<MAX_SHIELD_HITS; i++) {
                Shield_hits[i].type = SH_UNUSED;
                Shield_hits[i].objnum = -1;
        }

        for (i=0; i<MAX_SHIELD_TRI_BUFFER; i++) {
                Global_tris[i].used = 0;
                Global_tris[i].creation_time = Missiontime;
        }

        Num_multi_shield_points = 0;

        load_shield_hit_bitmap();
}

void release_shield_hit_bitmap()
{
        if ( !Shield_bitmaps_loaded )
                return;
}

int     Poly_count = 0;

void shield_hit_close()
{
        release_shield_hit_bitmap();
}

void shield_frame_init()
{
        Poly_count = 0;
        Num_shield_points = 0;
}

void create_low_detail_poly(int global_index, vec3d *tcp, vec3d *rightv, vec3d *upv)
{
        float           scale;
        gshield_tri     *trip;

        trip = &Global_tris[global_index];

        scale = vm_vec_mag(tcp) * 2.0f;

        vm_vec_scale_add(&trip->verts[0].pos, tcp, rightv, -scale/2.0f);
        vm_vec_scale_add2(&trip->verts[0].pos, upv, scale/2.0f);

        vm_vec_scale_add(&trip->verts[1].pos, &trip->verts[0].pos, rightv, scale);

        vm_vec_scale_add(&trip->verts[2].pos, &trip->verts[1].pos, upv, -scale);

        vm_vec_scale_add(&trip->verts[3].pos, &trip->verts[2].pos, rightv, -scale);

        //      Set u, v coordinates.
        //      Note, this need only be done once, as it's common for all explosions.
        trip->verts[0].u = 0.0f;
        trip->verts[0].v = 0.0f;

        trip->verts[1].u = 1.0f;
        trip->verts[1].v = 0.0f;

        trip->verts[2].u = 1.0f;
        trip->verts[2].v = 1.0f;

        trip->verts[3].u = 0.0f;
        trip->verts[3].v = 1.0f;

}

void rs_compute_uvs(shield_tri *stp, shield_vertex *verts, vec3d *tcp, float radius, vec3d *rightv, vec3d *upv)
{
        int     i;
        shield_vertex *sv;

        for (i=0; i<3; i++) {
                vec3d   v2cp;

                sv = &verts[stp->verts[i]];

                vm_vec_sub(&v2cp, &sv->pos, tcp);
                sv->u = vm_vec_dot(&v2cp, rightv) * Shield_scale + 0.5f;
                sv->v = - vm_vec_dot(&v2cp, upv) * Shield_scale + 0.5f;

        CLAMP(sv->u, 0.0f, UV_MAX);
        CLAMP(sv->v, 0.0f, UV_MAX);
        }
}

void free_global_tri_records(int shnum)
{
        int     i;

        Assert((shnum >= 0) && (shnum < MAX_SHIELD_HITS));

        for (i=0; i<Shield_hits[shnum].num_tris; i++){
                Global_tris[Shield_hits[shnum].tri_list[i]].used = 0;
        }
}

extern int Cmdline_nohtl;

void render_low_detail_shield_bitmap(gshield_tri *trip, matrix *orient, vec3d *pos, ubyte r, ubyte g, ubyte b)
{
        int             j;
        vec3d   pnt;
        vertex  verts[4];
    
    memset(verts, 0, sizeof(verts));

        for (j=0; j<4; j++ )    {
                // Rotate point into world coordinates
                vm_vec_unrotate(&pnt, &trip->verts[j].pos, orient);
                vm_vec_add2(&pnt, pos);

                // Pnt is now the x,y,z world coordinates of this vert.
                if(!Cmdline_nohtl) g3_transfer_vertex(&verts[j], &pnt);
                else g3_rotate_vertex(&verts[j], &pnt);
                verts[j].texture_position.u = trip->verts[j].u;
                verts[j].texture_position.v = trip->verts[j].v;
        }       

        verts[0].r = r;
        verts[0].g = g;
        verts[0].b = b;
        verts[1].r = r;
        verts[1].g = g;
        verts[1].b = b;
        verts[2].r = r;
        verts[2].g = g;
        verts[2].b = b;
        verts[3].r = r;
        verts[3].g = g;
        verts[3].b = b;

        vec3d   norm;
        vm_vec_perp(&norm, &trip->verts[0].pos, &trip->verts[1].pos, &trip->verts[2].pos);
        vertex  *vertlist[4];
        if ( vm_vec_dot(&norm, &trip->verts[1].pos ) < 0.0 )    {
                vertlist[0] = &verts[3]; 
                vertlist[1] = &verts[2];
                vertlist[2] = &verts[1]; 
                vertlist[3] = &verts[0]; 
                g3_draw_poly( 4, vertlist, TMAP_FLAG_TEXTURED | TMAP_FLAG_RGB | TMAP_FLAG_GOURAUD | TMAP_HTL_3D_UNLIT);
        } else {
                vertlist[0] = &verts[0]; 
                vertlist[1] = &verts[1];
                vertlist[2] = &verts[2]; 
                vertlist[3] = &verts[3]; 
                g3_draw_poly( 4, vertlist, TMAP_FLAG_TEXTURED | TMAP_FLAG_RGB | TMAP_FLAG_GOURAUD | TMAP_HTL_3D_UNLIT);
        }
}

void render_shield_triangle(gshield_tri *trip, matrix *orient, vec3d *pos, ubyte r, ubyte g, ubyte b)
{
        int             j;
        vec3d   pnt;
        vertex  *verts[3];
        vertex  points[3];
    
    memset(&verts, 0, sizeof(verts));

        if (trip->trinum == -1)
                return; //      Means this is a quad, must have switched detail_level.

        for (j=0; j<3; j++ )    {
                // Rotate point into world coordinates
                vm_vec_unrotate(&pnt, &trip->verts[j].pos, orient);
                vm_vec_add2(&pnt, pos);

                // Pnt is now the x,y,z world coordinates of this vert.
                // For this example, I am just drawing a sphere at that point.

                if (!Cmdline_nohtl) g3_transfer_vertex(&points[j],&pnt);
                else g3_rotate_vertex(&points[j], &pnt);
                        
                points[j].texture_position.u = trip->verts[j].u;
                points[j].texture_position.v = trip->verts[j].v;
                Assert((trip->verts[j].u >= 0.0f) && (trip->verts[j].u <= UV_MAX));
                Assert((trip->verts[j].v >= 0.0f) && (trip->verts[j].v <= UV_MAX));
                verts[j] = &points[j];
        }

        verts[0]->r = r;
        verts[0]->g = g;
        verts[0]->b = b;
        verts[1]->r = r;
        verts[1]->g = g;
        verts[1]->b = b;
        verts[2]->r = r;
        verts[2]->g = g;
        verts[2]->b = b;

        vec3d   norm;
        Poly_count++;
        vm_vec_perp(&norm,&verts[0]->world,&verts[1]->world,&verts[2]->world);

        int flags=TMAP_FLAG_TEXTURED | TMAP_FLAG_RGB | TMAP_FLAG_GOURAUD;
        if (!Cmdline_nohtl) flags |= TMAP_HTL_3D_UNLIT;

        if ( vm_vec_dot(&norm,&verts[1]->world ) >= 0.0 )       {
                vertex  *vertlist[3];
                vertlist[0] = verts[2]; 
                vertlist[1] = verts[1]; 
                vertlist[2] = verts[0]; 
                g3_draw_poly( 3, vertlist, flags);
        } else {
                g3_draw_poly( 3, verts, flags);
        }
}

MONITOR(NumShieldRend)


void render_shield(int shield_num)
{
        int             i;
        vec3d   *centerp;
        matrix  *orient;
        object  *objp;
        ship            *shipp;
        ship_info       *si;

        if (Shield_hits[shield_num].type == SH_UNUSED)  {
                return;
        }

        Assert(Shield_hits[shield_num].objnum >= 0);

        objp = &Objects[Shield_hits[shield_num].objnum];

        if (objp->flags & OF_NO_SHIELDS)        {
                return;
        }

        //      If this object didn't get rendered, don't render its shields.  In fact, make the shield hit go away.
        if (!(objp->flags & OF_WAS_RENDERED)) {
                Shield_hits[shield_num].type = SH_UNUSED;
                return;
        }

        //      At detail levels 1, 3, animations play at double speed to reduce load.
        if ( (Detail.shield_effects == 1) || (Detail.shield_effects == 3) ) {
                Shield_hits[shield_num].start_time -= Frametime;
        }

        MONITOR_INC(NumShieldRend,1);

        shipp = &Ships[objp->instance];
        si = &Ship_info[shipp->ship_info_index];
        // objp, shipp, and si are now setup correctly

        //      If this ship is in its deathroll, make the shield hit effects go away faster.
        if (shipp->flags & SF_DYING)    {
                Shield_hits[shield_num].start_time -= fl2f(2*flFrametime);
        }

        //      Detail level stuff.  When lots of shield hits, maybe make them go away faster.
        if (Poly_count > 50) {
                if (Shield_hits[shield_num].start_time + (SHIELD_HIT_DURATION*50)/Poly_count < Missiontime) {
                        Shield_hits[shield_num].type = SH_UNUSED;
                        free_global_tri_records(shield_num);
                        return;
                }
        } else if ((Shield_hits[shield_num].start_time + SHIELD_HIT_DURATION) < Missiontime) {
                Shield_hits[shield_num].type = SH_UNUSED;
                free_global_tri_records(shield_num);
                return;
        }

        orient = &objp->orient;
        centerp = &objp->pos;

        int bitmap_id, frame_num;

        // Do some sanity checking
        Assert( (si->species >= 0) && (si->species < (int)Species_info.size()) );

        generic_anim *sa = &Species_info[si->species].shield_anim;

        // don't try to draw if we don't have an ani
        if ( sa->first_frame >= 0 )
        {
                frame_num = fl2i( f2fl(Missiontime - Shield_hits[shield_num].start_time) / f2fl(SHIELD_HIT_DURATION) * sa->num_frames );
                if ( frame_num >= sa->num_frames )      {
                        frame_num = sa->num_frames - 1;
                } else if ( frame_num < 0 )     {
                        mprintf(( "HEY! Missiontime went backwards! (Shield.cpp)\n" ));
                        frame_num = 0;
                }
                bitmap_id = sa->first_frame + frame_num;

                float alpha = 0.9999f;
                if(The_mission.flags & MISSION_FLAG_FULLNEB){
                        alpha *= 0.85f;
                }

                gr_set_bitmap(bitmap_id, GR_ALPHABLEND_FILTER, GR_BITBLT_MODE_NORMAL, alpha );

                if ( (Detail.shield_effects == 1) || (Detail.shield_effects == 2) ) {
                        if ( bitmap_id != - 1 ) {
                                render_low_detail_shield_bitmap(&Global_tris[Shield_hits[shield_num].tri_list[0]], orient, centerp, Shield_hits[shield_num].rgb[0], Shield_hits[shield_num].rgb[1], Shield_hits[shield_num].rgb[2]);
                        }
                } else {
                        if ( bitmap_id != - 1 ) {
                                for (i=0; i<Shield_hits[shield_num].num_tris; i++) {
                                        render_shield_triangle(&Global_tris[Shield_hits[shield_num].tri_list[i]], orient, centerp, Shield_hits[shield_num].rgb[0], Shield_hits[shield_num].rgb[1], Shield_hits[shield_num].rgb[2]);
                                }
                        }
                }
        }
}

void render_shields()
{
        int     i;

        if (Detail.shield_effects == 0){
                return; //      No shield effect rendered at lowest detail level.
        }

        for (i=0; i<MAX_SHIELD_HITS; i++){
                if (Shield_hits[i].type != SH_UNUSED){
                        render_shield(i);
                }
        }
}

void create_tris_containing(vec3d *vp, matrix *orient, shield_info *shieldp, vec3d *tcp, vec3d *centerp, float radius, vec3d *rvec, vec3d *uvec)
{
        int     i, j;
        shield_vertex *verts;

        verts = shieldp->verts;

        for (i=0; i<Num_tris; i++) {
                if ( !shieldp->tris[i].used ) {
                        for (j=0; j<3; j++) {
                                vec3d v;

                                v = verts[shieldp->tris[i].verts[j]].pos;
                                if ((vp->xyz.x == v.xyz.x) && (vp->xyz.y == v.xyz.y) && (vp->xyz.z == v.xyz.z))
                                        create_shield_from_triangle(i, orient, shieldp, tcp, centerp, radius, rvec, uvec);
                        }
                }
        }
}

void visit_children(int trinum, int vertex_index, matrix *orient, shield_info *shieldp, vec3d *tcp, vec3d *centerp, float radius, vec3d *rvec, vec3d *uvec)
{
        shield_vertex *sv;

        sv = &(shieldp->verts[shieldp->tris[trinum].verts[vertex_index]]);

        if ( (sv->u > 0.0f) && (sv->u < UV_MAX) && (sv->v > 0.0f) && (sv->v < UV_MAX))
                        create_tris_containing(&sv->pos, orient, shieldp, tcp, centerp, radius, rvec, uvec);
}

int     Gi_max = 0;

int get_free_global_shield_index()
{
        int     gi = 0;

        while ((gi < MAX_SHIELD_TRI_BUFFER) && (Global_tris[gi].used) && (Global_tris[gi].creation_time + SHIELD_HIT_DURATION > Missiontime)) {
                gi++;
        }

        //      If couldn't find one, choose a random one.
        if (gi == MAX_SHIELD_TRI_BUFFER)
                gi = (int) (frand() * MAX_SHIELD_TRI_BUFFER);

        return gi;
}

int get_global_shield_tri()
{
        int     shnum;

        //      Find unused shield hit buffer
        for (shnum=0; shnum<MAX_SHIELD_HITS; shnum++)
                if (Shield_hits[shnum].type == SH_UNUSED)
                        break;

        if (shnum == MAX_SHIELD_HITS) {
                shnum = myrand() % MAX_SHIELD_HITS;
        }

        Assert((shnum >= 0) && (shnum < MAX_SHIELD_HITS));

        return shnum;
}

void create_shield_from_triangle(int trinum, matrix *orient, shield_info *shieldp, vec3d *tcp, vec3d *centerp, float radius, vec3d *rvec, vec3d *uvec)
{
        rs_compute_uvs( &shieldp->tris[trinum], shieldp->verts, tcp, radius, rvec, uvec);

        shieldp->tris[trinum].used = 1;

        visit_children(trinum, 0, orient, shieldp, tcp, centerp, radius, rvec, uvec);
        visit_children(trinum, 1, orient, shieldp, tcp, centerp, radius, rvec, uvec);
        visit_children(trinum, 2, orient, shieldp, tcp, centerp, radius, rvec, uvec);
}

void copy_shield_to_globals( int objnum, shield_info *shieldp )
{
        int     i, j;
        int     gi = 0;
        int     count = 0;                      //      Number of triangles in this shield hit.
        int     shnum;                          //      shield hit number, index in Shield_hits.

        shnum = get_global_shield_tri();
        
        Shield_hits[shnum].type = SH_TYPE_1;

        for (i = 0; i < shieldp->ntris; i++ ) {
                if ( shieldp->tris[i].used ) {
                        while ( (gi < MAX_SHIELD_TRI_BUFFER) && (Global_tris[gi].used) && (Global_tris[gi].creation_time + SHIELD_HIT_DURATION > Missiontime)) {
                                gi++;
                        }
                        
                        //      If couldn't find one, choose a random one.
                        if (gi == MAX_SHIELD_TRI_BUFFER)
                                gi = (int) (frand() * MAX_SHIELD_TRI_BUFFER);

                        Global_tris[gi].used = shieldp->tris[i].used;
                        Global_tris[gi].trinum = i;
                        Global_tris[gi].creation_time = Missiontime;

                        // copy the pos/u/v elements of the shield_vertex structure into the shield vertex structure for this global triangle.
                        for (j = 0; j < 3; j++)
                                Global_tris[gi].verts[j] = shieldp->verts[shieldp->tris[i].verts[j]];
                        Shield_hits[shnum].tri_list[count++] = gi;

                        if (count >= MAX_TRIS_PER_HIT) {
                                mprintf(("Warning: Too many triangles in shield hit.\n"));
                                break;
                        }
                }
        }

        Shield_hits[shnum].num_tris = count;
        Shield_hits[shnum].start_time = Missiontime;
        Shield_hits[shnum].objnum = objnum;

        Shield_hits[shnum].rgb[0] = 255;
        Shield_hits[shnum].rgb[1] = 255;
        Shield_hits[shnum].rgb[2] = 255;
        if((objnum >= 0) && (objnum < MAX_OBJECTS) && (Objects[objnum].type == OBJ_SHIP) && (Objects[objnum].instance >= 0) && (Objects[objnum].instance < MAX_SHIPS) && (Ships[Objects[objnum].instance].ship_info_index >= 0) && (Ships[Objects[objnum].instance].ship_info_index < static_cast<int>(Ship_info.size()))){
                ship_info *sip = &Ship_info[Ships[Objects[objnum].instance].ship_info_index];
                
                Shield_hits[shnum].rgb[0] = sip->shield_color[0];
                Shield_hits[shnum].rgb[1] = sip->shield_color[1];
                Shield_hits[shnum].rgb[2] = sip->shield_color[2];
        }
}


float apply_damage_to_shield(object *objp, int quadrant, float damage)
{
        ai_info *aip;

        // multiplayer clients bail here
        if(MULTIPLAYER_CLIENT){
                return damage;
        }

        if ( (quadrant < 0)  || (quadrant >= objp->n_quadrants) ) return damage;        
        
        Assert(objp->type == OBJ_SHIP);
        aip = &Ai_info[Ships[objp->instance].ai_index];
        aip->last_hit_quadrant = quadrant;

        objp->shield_quadrant[quadrant] -= damage;

        if (objp->shield_quadrant[quadrant] < 0.0f) {
                float   remaining_damage;

                remaining_damage = -objp->shield_quadrant[quadrant];
                objp->shield_quadrant[quadrant] = 0.0f;
                return remaining_damage;
        } else {
                return 0.0f;
        }
                
}

void create_shield_low_detail(int objnum, int model_num, matrix *orient, vec3d *centerp, vec3d *tcp, int tr0, shield_info *shieldp)
{
        matrix  tom;
        int             gi;
        int             shnum;

        shnum = get_global_shield_tri();
        Shield_hits[shnum].type = SH_TYPE_1;

        gi = get_free_global_shield_index();

        Global_tris[gi].used = 1;
        Global_tris[gi].trinum = -1;            //      This tells triangle renderer to not render in case detail_level was switched.
        Global_tris[gi].creation_time = Missiontime;

        Shield_hits[shnum].tri_list[0] = gi;
        Shield_hits[shnum].num_tris = 1;
        Shield_hits[shnum].start_time = Missiontime;
        Shield_hits[shnum].objnum = objnum;

        Shield_hits[shnum].rgb[0] = 255;
        Shield_hits[shnum].rgb[1] = 255;
        Shield_hits[shnum].rgb[2] = 255;
        if((objnum >= 0) && (objnum < MAX_OBJECTS) && (Objects[objnum].type == OBJ_SHIP) && (Objects[objnum].instance >= 0) && (Objects[objnum].instance < MAX_SHIPS) && (Ships[Objects[objnum].instance].ship_info_index >= 0) && (Ships[Objects[objnum].instance].ship_info_index < static_cast<int>(Ship_info.size()))){
                ship_info *sip = &Ship_info[Ships[Objects[objnum].instance].ship_info_index];
                
                Shield_hits[shnum].rgb[0] = sip->shield_color[0];
                Shield_hits[shnum].rgb[1] = sip->shield_color[1];
                Shield_hits[shnum].rgb[2] = sip->shield_color[2];
        }

        vm_vector_2_matrix(&tom, &shieldp->tris[tr0].norm, NULL, NULL);

        create_low_detail_poly(gi, tcp, &tom.vec.rvec, &tom.vec.uvec);
}

// Algorithm for shrink-wrapping a texture across a triangular mesh.
// 
// - Given a point of intersection, tcp (local to objnum)
// - Vector to center of shield from tcp is v2c.
// - Using v2c, compute right and down vectors.  These are the vectors of
//   increasing u and v, respectively.
// - Triangle of intersection of tcp is tr0.
// - For 3 points in tr0, compute u,v coordinates using up and down vectors
//   from center point, tcp.  Need to know size of explosion texture.  N units
//   along right vector corresponds to O units in explosion texture space.
// - For each edge, if either endpoint was outside texture bounds, recursively
//   apply previous and current step.
// 
// Output of above is a list of triangles with u,v coordinates.  These u,v
// coordinates will have to be clipped against the explosion texture bounds.

void create_shield_explosion(int objnum, int model_num, matrix *orient, vec3d *centerp, vec3d *tcp, int tr0)
{
        matrix  tom;            //      Texture Orientation Matrix
        shield_info     *shieldp;
        polymodel       *pm;
        int             i;

        if (Objects[objnum].flags & OF_NO_SHIELDS)
                return;

        pm = model_get(model_num);
        Num_tris = pm->shield.ntris;
        shieldp = &pm->shield;

        if (Num_tris == 0)
                return;

        if ( (Detail.shield_effects == 1) || (Detail.shield_effects == 2) ) {
                create_shield_low_detail(objnum, model_num, orient, centerp, tcp, tr0, shieldp);
                return;
        }

        for (i=0; i<Num_tris; i++)
                shieldp->tris[i].used = 0;

        //      Compute orientation matrix from normal of surface hit.
        //      Note, this will cause the shape of the bitmap to change abruptly
        //      as the impact point moves to another triangle.  To prevent this,
        //      you could average the normals at the vertices, then interpolate the
        //      normals from the vertices to get a smoothly changing normal across the face.
        //      I had tried using the vector from the impact point to the center, which
        //      changes smoothly, but this looked surprisingly bad.
        vm_vector_2_matrix(&tom, &shieldp->tris[tr0].norm, NULL, NULL);

        //      Create the shield from the current triangle, as well as its neighbors.
        create_shield_from_triangle(tr0, orient, shieldp, tcp, centerp, Objects[objnum].radius, &tom.vec.rvec, &tom.vec.uvec);

        for (i=0; i<3; i++)
                create_shield_from_triangle(shieldp->tris[tr0].neighbors[i], orient, shieldp, tcp, centerp, Objects[objnum].radius, &tom.vec.rvec, &tom.vec.uvec);
        
        copy_shield_to_globals(objnum, shieldp);
}

MONITOR(NumShieldHits)


void add_shield_point(int objnum, int tri_num, vec3d *hit_pos)
{
        if (Num_shield_points >= MAX_SHIELD_POINTS)
                return;

        Verify(objnum < MAX_OBJECTS);

        MONITOR_INC(NumShieldHits,1);

        Shield_points[Num_shield_points].objnum = objnum;
        Shield_points[Num_shield_points].shield_tri = tri_num;
        Shield_points[Num_shield_points].hit_point = *hit_pos;

        Num_shield_points++;

        Ships[Objects[objnum].instance].shield_hits++;
}

// ugh!  I wrote a special routine to store shield points for clients in multiplayer
// games.  Problem is initilization and flow control of normal gameplay make this problem
// more than trivial to solve.  Turns out that I think I can just keep track of the
// shield_points for multiplayer in a separate count -- then assign the multi count to
// the normal count at the correct time.
void add_shield_point_multi(int objnum, int tri_num, vec3d *hit_pos)
{
        if (Num_multi_shield_points >= MAX_SHIELD_POINTS)
                return;

        Shield_points[Num_shield_points].objnum = objnum;
        Shield_points[Num_shield_points].shield_tri = tri_num;
        Shield_points[Num_shield_points].hit_point = *hit_pos;

        Num_multi_shield_points++;
}

void shield_point_multi_setup()
{
        int i;

        Assert( MULTIPLAYER_CLIENT );

        if ( Num_multi_shield_points == 0 )
                return;

        Num_shield_points = Num_multi_shield_points;
        for (i = 0; i < Num_shield_points; i++ ){
                Ships[Objects[Shield_points[i].objnum].instance].shield_hits++;
        }

        Num_multi_shield_points = 0;
}


void create_shield_explosion_all(object *objp)
{
        int     i;
        int     num;
        int     count;
        int     objnum;
        ship    *shipp;

        if (Detail.shield_effects == 0){
                return; 
        }

        num = objp->instance;
        shipp = &Ships[num];

        count = shipp->shield_hits;
        objnum = objp-Objects;

        for (i=0; i<Num_shield_points; i++) {
                if (Shield_points[i].objnum == objnum) {
                        create_shield_explosion(objnum, Ship_info[shipp->ship_info_index].model_num, &objp->orient, &objp->pos, &Shield_points[i].hit_point, Shield_points[i].shield_tri);
                        count--;
                        if (count <= 0){
                                break;
                        }
                }
        }

        // some some reason, clients seem to have a bogus count valud on occation.  I"ll chalk it up
        // to missed packets :-)  MWA 2/6/98
        if ( !MULTIPLAYER_CLIENT ) {
                Assert(count == 0);     //      Couldn't find all the alleged shield hits.  Bogus!
        }
}

int     Break_value = -1;

#ifndef NDEBUG
void ship_draw_shield( object *objp)
{
        int             model_num;
        int             i;
        vec3d   pnt;
        polymodel * pm; 

        if (objp->flags & OF_NO_SHIELDS)
                return;

        Assert(objp->instance >= 0);

        model_num = Ship_info[Ships[objp->instance].ship_info_index].model_num;

        if ( Fred_running ) return;

        pm = model_get(model_num);

        if (pm->shield.ntris<1) return;

        //      Scan all the triangles in the mesh.
        for (i=0; i<pm->shield.ntris; i++ )     {
                int             j;
                vec3d   gnorm, v2f, tri_point;
                vertex prev_pnt, pnt0;
                shield_tri *tri;

                tri = &pm->shield.tris[i];

                if (i == Break_value)
                        Int3();

                //      Hack! Only works for object in identity orientation.
                //      Need to rotate eye position into object's reference frame.
                //      Only draw facing triangles.
                vm_vec_rotate(&tri_point, &pm->shield.verts[tri->verts[0]].pos, &Eye_matrix);
                vm_vec_add2(&tri_point, &objp->pos);

                vm_vec_sub(&v2f, &tri_point, &Eye_position);
                vm_vec_unrotate(&gnorm, &tri->norm, &objp->orient);

                if (vm_vec_dot(&gnorm, &v2f) < 0.0f) {
                        int     intensity;

                        intensity = (int) (Ships[objp->instance].shield_integrity[i] * 255);

                        if (intensity < 0)
                                intensity = 0;
                        else if (intensity > 255)
                                intensity = 255;
                        
                        gr_set_color(0, 0, intensity);

                        //      Process the vertices.
                        //      Note this rotates each vertex each time it's needed, very dumb.
                        for (j=0; j<3; j++ )    {
                                vertex tmp;

                                // Rotate point into world coordinates
                                vm_vec_unrotate(&pnt, &pm->shield.verts[tri->verts[j]].pos, &objp->orient);
                                vm_vec_add2(&pnt, &objp->pos);

                                // Pnt is now the x,y,z world coordinates of this vert.
                                // For this example, I am just drawing a sphere at that
                                // point.
                                g3_rotate_vertex(&tmp, &pnt);

                                if (j)
                                        g3_draw_line(&prev_pnt, &tmp);
                                else
                                        pnt0 = tmp;
                                prev_pnt = tmp;
                        }

                        g3_draw_line(&pnt0, &prev_pnt);
                }
        }
}
#endif

int ship_is_shield_up( object *obj, int quadrant )
{
        if ( (quadrant >= 0) && (quadrant < obj->n_quadrants))  {
                // Just check one quadrant
                if (obj->shield_quadrant[quadrant] > MAX(2.0f, 0.1f * get_max_shield_quad(obj)))        {
                        return 1;
                }
        } else {
                // Check all quadrants
                float strength = shield_get_strength(obj);

                if ( strength > MAX(2.0f*4.0f, 0.1f * Ships[obj->instance].ship_max_shield_strength ))  {
                        return 1;
                }
        }
        return 0;       // no shield strength
}

//      return quadrant containing hit_pnt.
//      \  1  /.
//      3 \ / 0
//        / \.
//      /  2  \.
//      Note: This is in the object's local reference frame.  Do _not_ pass a vector in the world frame.
int get_quadrant(vec3d *hit_pnt, object *shipobjp)
{
        if (shipobjp != NULL && Ship_info[Ships[shipobjp->instance].ship_info_index].flags2 & SIF2_MODEL_POINT_SHIELDS) {
                int closest = -1;
                float closest_dist = FLT_MAX;

                for (unsigned int i=0; i<Ships[shipobjp->instance].shield_points.size(); i++) {
                        float dist = vm_vec_dist(hit_pnt, &Ships[shipobjp->instance].shield_points.at(i));

                        if (dist < closest_dist) {
                                closest = i;
                                closest_dist = dist;
                        }
                }

                return closest;
        } else {
                int     result = 0;

                if (hit_pnt->xyz.x < hit_pnt->xyz.z)
                        result |= 1;

                if (hit_pnt->xyz.x < -hit_pnt->xyz.z)
                        result |= 2;

                return result;
        }
}