better physics

[carveJwlIkooP6JGAAIwe30JlM.git] / player_physics.h

/*
 * Copyright (C) 2021-2022 Mt.ZERO Software, Harry Godden - All Rights Reserved
 */

#ifndef PLAYER_PHYSICS_H
#define PLAYER_PHYSICS_H

#include "player.h"
#include "camera.h"

VG_STATIC void apply_gravity( v3f vel, float const timestep )
{
   v3f gravity = { 0.0f, -9.6f, 0.0f };
   v3_muladds( vel, gravity, timestep, vel );
}

/*
 * Called when launching into the air to predict and adjust trajectories
 */
VG_STATIC void player_start_air(void)
{
   struct player_phys *phys = &player.phys;

   if( phys->in_air )
      return;

   phys->in_air = 1;

   float pstep = VG_TIMESTEP_FIXED * 10.0f;
   float best_velocity_delta = -9999.9f;
   float k_bias = 0.96f;

   v3f axis;
   v3_cross( phys->rb.up, phys->rb.v, axis );
   v3_normalize( axis );
   player.land_log_count = 0;
   
   m3x3_identity( phys->vr );

   for( int m=-3;m<=12; m++ )
   {
      float vmod = ((float)m / 15.0f)*0.09f;

      v3f pco, pco1, pv;
      v3_copy( phys->rb.co, pco );
      v3_muls( phys->rb.v, k_bias, pv );

      /* 
       * Try different 'rotations' of the velocity to find the best possible
       * landing normal. This conserves magnitude at the expense of slightly
       * unrealistic results
       */

      m3x3f vr;
      v4f vr_q;

      q_axis_angle( vr_q, axis, vmod );
      q_m3x3( vr_q, vr );

      m3x3_mulv( vr, pv, pv );
      v3_muladds( pco, pv, pstep, pco );

      for( int i=0; i<50; i++ )
      {
         v3_copy( pco, pco1 );
         apply_gravity( pv, pstep );

         m3x3_mulv( vr, pv, pv );
         v3_muladds( pco, pv, pstep, pco );
         
         ray_hit contact;
         v3f vdir;

         v3_sub( pco, pco1, vdir );
         contact.dist = v3_length( vdir );
         v3_divs( vdir, contact.dist, vdir);

         if( ray_world( pco1, vdir, &contact ))
         {
            float land_delta = v3_dot( pv, contact.normal );
            u32 scolour = (u8)(vg_minf(-land_delta * 2.0f, 255.0f));

            /* Bias prediction towords ramps */
            if( ray_hit_material( &contact )->info.flags 
                  & k_material_flag_skate_surface )
            {
               land_delta *= 0.1f;
               scolour |= 0x0000a000;
            }

            if( (land_delta < 0.0f) && (land_delta > best_velocity_delta) )
            {
               best_velocity_delta = land_delta;

               v3_copy( contact.pos, player.land_target );
               
               m3x3_copy( vr, phys->vr_pstep );
               q_axis_angle( vr_q, axis, vmod*0.1f );
               q_m3x3( vr_q, phys->vr );
            }

            v3_copy( contact.pos, 
                  player.land_target_log[player.land_log_count] );
            player.land_target_colours[player.land_log_count] = 
               0xff000000 | scolour;

            player.land_log_count ++;

            break;
         }
      }
   }
}

/*
 * Main friction interface model
 */
VG_STATIC void player_physics_control(void)
{
   struct player_phys *phys = &player.phys;

   /*
    * Computing localized friction forces for controlling the character
    * Friction across X is significantly more than Z
    */

   v3f vel;
   m3x3_mulv( phys->rb.to_local, phys->rb.v, vel );
   float slip = 0.0f;
   
   if( fabsf(vel[2]) > 0.01f )
      slip = fabsf(-vel[0] / vel[2]) * vg_signf(vel[0]);

   if( fabsf( slip ) > 1.2f )
      slip = vg_signf( slip ) * 1.2f;
   phys->slip = slip;
   phys->reverse = -vg_signf(vel[2]);

   float substep = VG_TIMESTEP_FIXED * 0.2f;

#if 0
   float fwd_resistance = vg_get_button( "break" )? 5.0f: k_friction_resistance;
#else
   float fwd_resistance = k_friction_resistance;
#endif

   for( int i=0; i<5; i++ )
   {
      vel[2] = stable_force( vel[2],vg_signf(vel[2]) * -fwd_resistance*substep);
      vel[0] = stable_force( vel[0],vg_signf(vel[0]) * -k_friction_lat*substep);
   }
   
   if( player.input_jump->button.value )
   {
      phys->jump += VG_TIMESTEP_FIXED * k_jump_charge_speed;

      if( !phys->jump_charge )
         phys->jump_dir = phys->reverse > 0.0f? 1: 0;

      phys->jump_charge = 1;
   }

   static int push_thresh_last = 0;
   float push = player.input_push->axis.value;
   int push_thresh = push>0.15f? 1: 0;
   
   if( push_thresh && !push_thresh_last )
      player.phys.start_push = vg.time;

   push_thresh_last = push_thresh;

   if( !player.input_jump->button.value && push_thresh )
   {
      player.phys.pushing = 1.0f;
      player.phys.push_time = vg.time - player.phys.start_push;

      float cycle_time = player.phys.push_time*k_push_cycle_rate,
            amt = k_push_accel * (sinf(cycle_time)*0.5f+0.5f)*VG_TIMESTEP_FIXED,
            current = v3_length( vel ),
            new_vel = vg_minf( current + amt, k_max_push_speed );

      new_vel -= vg_minf(current, k_max_push_speed);
      vel[2] -= new_vel * phys->reverse;
   }

   /* Pumping */
   static float previous = 0.0f;
   float delta = previous - phys->grab,
          pump = delta * k_pump_force * VG_TIMESTEP_FIXED;
   previous = phys->grab;

   v3f p1;
   v3_muladds( phys->rb.co, phys->rb.up, pump, p1 );
   vg_line( phys->rb.co, p1, 0xff0000ff );

   vel[1] += pump;

   
   m3x3_mulv( phys->rb.to_world, vel, phys->rb.v );
   
   float steer = player.input_js1h->axis.value,
         steer_scaled = vg_signf(steer) * powf(steer,2.0f) * k_steer_ground;

   phys->iY -= steer_scaled * VG_TIMESTEP_FIXED;
}

/*
 * Air control, no real physics
 */
VG_STATIC void player_physics_control_air(void)
{
   struct player_phys *phys = &player.phys;

   m3x3_mulv( phys->vr, phys->rb.v, phys->rb.v );
   vg_line_cross( player.land_target, 0xff0000ff, 0.25f );

   ray_hit hit;

   /* 
    * Prediction 
    */
   float pstep = VG_TIMESTEP_FIXED * 10.0f;

   v3f pco, pco1, pv;
   v3_copy( phys->rb.co, pco );
   v3_copy( phys->rb.v, pv );
   
   float time_to_impact = 0.0f;
   float limiter = 1.0f;

   for( int i=0; i<50; i++ )
   {
      v3_copy( pco, pco1 );
      m3x3_mulv( phys->vr_pstep, pv, pv );
      apply_gravity( pv, pstep );
      v3_muladds( pco, pv, pstep, pco );
      
      ray_hit contact;
      v3f vdir;

      v3_sub( pco, pco1, vdir );
      contact.dist = v3_length( vdir );
      v3_divs( vdir, contact.dist, vdir);
      
      float orig_dist = contact.dist;
      if( ray_world( pco1, vdir, &contact ))
      {
         float angle = v3_dot( phys->rb.up, contact.normal );
         v3f axis; 
         v3_cross( phys->rb.up, contact.normal, axis );

         time_to_impact += (contact.dist/orig_dist)*pstep;
         limiter = vg_minf( 5.0f, time_to_impact )/5.0f;
         limiter = 1.0f-limiter;
         limiter *= limiter;
         limiter = 1.0f-limiter;

         if( angle < 0.99f )
         {
            v4f correction;
            q_axis_angle( correction, axis, 
                  acosf(angle)*(1.0f-limiter)*3.0f*VG_TIMESTEP_FIXED );
            q_mul( correction, phys->rb.q, phys->rb.q );
         }

         vg_line_cross( contact.pos, 0xffff0000, 0.25f );
         break;
      }
      time_to_impact += pstep;
   }

   float steerh = player.input_js1h->axis.value,
         steerv = player.input_js1v->axis.value;

   phys->iY -= steerh * k_steer_air * VG_TIMESTEP_FIXED;

   {
      float iX = steerv * 
                 phys->reverse * k_steer_air * limiter * VG_TIMESTEP_FIXED;

      static float siX = 0.0f;
      siX = vg_lerpf( siX, iX, k_steer_air_lerp );
      
      v4f rotate;
      q_axis_angle( rotate, phys->rb.right, siX );
      q_mul( rotate, phys->rb.q, phys->rb.q );
   }
   
#if 0
   v2f target = {0.0f,0.0f};
   v2_muladds( target, (v2f){ vg_get_axis("grabh"), vg_get_axis("grabv") },
               phys->grab, target );
#endif
}

VG_STATIC void player_walk_update_collision(void)
{
   struct player_phys *phys = &player.phys;
   float h0 = 0.3f,
         h1 = 0.9f;

   rigidbody *rbf = &player.collide_front,
             *rbb = &player.collide_back;

   v3_add( phys->rb.co, (v3f){0.0f,h0,0.0f}, rbf->co );
   v3_add( phys->rb.co, (v3f){0.0f,h1,0.0f}, rbb->co );
   v3_copy( rbf->co, rbf->to_world[3] );
   v3_copy( rbb->co, rbb->to_world[3] );
   m4x3_invert_affine( rbf->to_world, rbf->to_local );
   m4x3_invert_affine( rbb->to_world, rbb->to_local );

   rb_update_bounds( rbf );
   rb_update_bounds( rbb );
}

VG_STATIC void player_integrate(void);
/*
 * Entire Walking physics model
 * TODO: sleep when under certain velotiy
 */
VG_STATIC void player_walk_physics(void)
{
   struct player_phys *phys = &player.phys;
   rigidbody *rbf = &player.collide_front,
             *rbb = &player.collide_back;

   m3x3_identity( player.collide_front.to_world );
   m3x3_identity( player.collide_back.to_world );

   v3_zero( phys->rb.w );
   q_axis_angle( phys->rb.q, (v3f){0.0f,1.0f,0.0f}, -player.angles[0] );

   rb_ct manifold[64];
   int len;

   v3f forward_dir = { sinf(player.angles[0]),0.0f,-cosf(player.angles[0]) };
   v3f right_dir = { -forward_dir[2], 0.0f, forward_dir[0] };

   if( phys->in_air )
   {
      player_walk_update_collision();
      rb_debug( rbf, 0xff0000ff );
      rb_debug( rbb, 0xff0000ff );

      len = 0;
      len += rb_sphere_scene( rbf, &world.rb_geo, manifold+len );
      len += rb_sphere_scene( rbb, &world.rb_geo, manifold+len );
      rb_presolve_contacts( manifold, len );

      for( int i=0; i<len; i++ )
      {
         struct contact *ct = &manifold[i];
         if( v3_dot( ct->n, (v3f){0.0f,1.0f,0.0f} ) > 0.5f )
            phys->in_air = 0;
      }

      for( int j=0; j<5; j++ )
      {
         for( int i=0; i<len; i++ )
         {
            struct contact *ct = &manifold[i];
            
            /*normal */
            float vn = -v3_dot( phys->rb.v, ct->n );
            vn += ct->bias;

            float temp = ct->norm_impulse;
            ct->norm_impulse = vg_maxf( temp + vn, 0.0f );
            vn = ct->norm_impulse - temp;

            v3f impulse;
            v3_muls( ct->n, vn, impulse );

            v3_add( impulse, phys->rb.v, phys->rb.v );

            /* friction */
            for( int j=0; j<2; j++ )
            {
               float     f = k_friction * ct->norm_impulse,
                        vt = v3_dot( phys->rb.v, ct->t[j] ),
                    lambda = -vt;
               
               float temp = ct->tangent_impulse[j];
               ct->tangent_impulse[j] = vg_clampf( temp + lambda, -f, f );
               lambda = ct->tangent_impulse[j] - temp;

               v3_muladds( phys->rb.v, ct->t[j], lambda, phys->rb.v );
            }
         }
      }

      player_integrate();
   }
   else
   {
      /* translate player */
      v2f walk = { player.input_walkh->axis.value,
                   player.input_walkv->axis.value };
      
      if( v2_length2(walk) > 0.001f )
         v2_normalize( walk );

      v2_muls( walk, vg_maxf( player.input_push->axis.value, 0.5f ) *
                        k_walkspeed * VG_TIMESTEP_FIXED, walk );

      v3f walk_apply;
      v3_zero( walk_apply );

      /* Do XY translation */
      v3_muladds( walk_apply, right_dir,   walk[0], walk_apply );
      v3_muladds( walk_apply, forward_dir, walk[1], walk_apply );
      v3_add( walk_apply, phys->rb.co, phys->rb.co );
      v3_divs( walk_apply, VG_TIMESTEP_FIXED, phys->rb.v );

      /* Directly resolve collisions */
      player_walk_update_collision();
      rb_debug( rbf, 0xffffff00 );
      rb_debug( rbb, 0xffffff00 );

      len = 0;
      len += rb_sphere_scene( rbf, &world.rb_geo, manifold+len );
      len += rb_sphere_scene( rbb, &world.rb_geo, manifold+len );

      v3f dt;
      v3_zero( dt );
      for( int j=0; j<3; j++ )
      {
         for( int i=0; i<len; i++ )
         {
            struct contact *ct = &manifold[i];

            float p   = vg_maxf( 0.0f, ct->p - 0.00f ),
                  cur = vg_clampf( v3_dot( ct->n, dt ), 0.0f, p );
            v3_muladds( dt, ct->n, (p - cur) * 0.333333333f, dt );
         }
      }
      v3_add( dt, phys->rb.co, phys->rb.co );

      /* jump */
      if( player.input_jump->button.value )
      {
         phys->rb.v[1] = 5.0f;
         phys->in_air = 1;
         return;
      }
      
      /* if we've put us in the air, step down slowly */
      phys->in_air = 1;
      float max_dist = 0.3f,
            start_y = phys->rb.co[1];

      for( int j=0; j<8; j++ )
      {
         for( int i=0; i<len; i++ )
         {
            struct contact *ct = &manifold[i];
            if( v3_dot( ct->n, (v3f){0.0f,1.0f,0.0f} ) > 0.5f )
            {
               phys->in_air = 0;
               if( j == 0 )
                  return;

               v3f dt;
               v3_zero( dt );
               for( int j=0; j<3; j++ )
               {
                  for( int i=0; i<len; i++ )
                  {
                     struct contact *ct = &manifold[i];

                     float p   = vg_maxf( 0.0f, ct->p - 0.0025f ),
                           cur = vg_clampf( v3_dot( ct->n, dt ), 0.0f, p );
                     v3_muladds( dt, ct->n, (p - cur) * 0.333333333f, dt );
                  }
               }
               v3_add( dt, phys->rb.co, phys->rb.co );
               return;
            }
         }

         phys->rb.co[1] -= max_dist * 0.125f;

         player_walk_update_collision();
         len = 0;
         len += rb_sphere_scene( rbf, &world.rb_geo, manifold+len );
         len += rb_sphere_scene( rbb, &world.rb_geo, manifold+len );
      }
      
      /* Transitioning into air mode */
      phys->rb.co[1] = start_y;
   }
}

/*
 * Physics collision detection, and control
 */
VG_STATIC void player_physics(void)
{
   struct player_phys *phys = &player.phys;
   /*
    * Update collision fronts
    */
   
   rigidbody *rbf = &player.collide_front,
             *rbb = &player.collide_back;

   m3x3_copy( phys->rb.to_world, player.collide_front.to_world );
   m3x3_copy( phys->rb.to_world, player.collide_back.to_world );
   
   player.air_blend = vg_lerpf( player.air_blend, phys->in_air, 0.1f );
   float h = player.air_blend*0.2f;

   m4x3_mulv( phys->rb.to_world, (v3f){0.0f,h,-k_board_length}, rbf->co );
   v3_copy( rbf->co, rbf->to_world[3] );
   m4x3_mulv( phys->rb.to_world, (v3f){0.0f,h, k_board_length}, rbb->co );
   v3_copy( rbb->co, rbb->to_world[3] );

   m4x3_invert_affine( rbf->to_world, rbf->to_local );
   m4x3_invert_affine( rbb->to_world, rbb->to_local );

   rb_update_bounds( rbf );
   rb_update_bounds( rbb );

   rb_debug( rbf, 0xff00ffff );
   rb_debug( rbb, 0xffffff00 );

   rb_ct manifold[64];
   int len = 0;

   len += rb_sphere_scene( rbf, &world.rb_geo, manifold+len );
   len += rb_sphere_scene( rbb, &world.rb_geo, manifold+len );

   rb_presolve_contacts( manifold, len );
   v3f surface_avg = {0.0f, 0.0f, 0.0f};

   if( !len )
   {
      player_start_air();
   }
   else
   {
      for( int i=0; i<len; i++ )
      {
         v3_add( manifold[i].n, surface_avg, surface_avg );
      }

      v3_normalize( surface_avg );

      if( v3_dot( phys->rb.v, surface_avg ) > 0.5f )
      {
         player_start_air();
      }
      else
      {
         phys->in_air = 0;
      }
   }

   for( int j=0; j<5; j++ )
   {
      for( int i=0; i<len; i++ )
      {
         struct contact *ct = &manifold[i];
         
         v3f dv, delta;
         v3_sub( ct->co, phys->rb.co, delta ); 
         v3_cross( phys->rb.w, delta, dv );
         v3_add( phys->rb.v, dv, dv );

         float vn = -v3_dot( dv, ct->n );
         vn += ct->bias;

         float temp = ct->norm_impulse;
         ct->norm_impulse = vg_maxf( temp + vn, 0.0f );
         vn = ct->norm_impulse - temp;

         v3f impulse;
         v3_muls( ct->n, vn, impulse );

         if( fabsf(v3_dot( impulse, phys->rb.forward )) > 10.0f ||
             fabsf(v3_dot( impulse, phys->rb.up )) > 50.0f )
         {
            player_kill();
            return;
         }

         v3_add( impulse, phys->rb.v, phys->rb.v );
         v3_cross( delta, impulse, impulse );

         /*
          * W Impulses are limited to the Y and X axises, we don't really want
          * roll angular velocities being included.
          *
          * Can also tweak the resistance of each axis here by scaling the wx,wy
          * components.
          */
         
         float wy = v3_dot( phys->rb.up, impulse ),
               wx = v3_dot( phys->rb.right, impulse )*1.5f;

         v3_muladds( phys->rb.w, phys->rb.up, wy, phys->rb.w );
         v3_muladds( phys->rb.w, phys->rb.right, wx, phys->rb.w );
      }
   }

   float grabt = vg_maxf( player.input_grab->axis.value,
                     vg_maxf( fabsf( player.input_emjs2h->axis.value ),
                              fabsf( player.input_emjs2v->axis.value ) )
                  );

   phys->grab = vg_lerpf( phys->grab, grabt, 0.14f );
   player.phys.pushing = 0.0f;

   if( !phys->in_air )
   {
#if 0
      v3f axis;
      float angle = v3_dot( phys->rb.up, surface_avg );
      v3_cross( phys->rb.up, surface_avg, axis );

      //float cz = v3_dot( player.rb.forward, axis );
      //v3_muls( player.rb.forward, cz, axis );

      if( angle < 0.999f )
      {
         v4f correction;
         q_axis_angle( correction, axis, acosf(angle)*18.0f*VG_TIMESTEP_FIXED );
         q_mul( correction, phys->rb.q, phys->rb.q );
      }
#else
      
      /* 20/10/22: make this only go axisways instead, may effect velocities. */

      v3f projected, axis;

      float d = v3_dot( phys->rb.forward, surface_avg );
      v3_muladds( surface_avg, phys->rb.forward, -d, projected );
      v3_normalize( projected );

      float angle = v3_dot( phys->rb.up, projected );
      v3_cross( phys->rb.up, projected, axis );

      v3f p0, p1;
      v3_add( phys->rb.co, projected, p0 );
      v3_add( phys->rb.co, phys->rb.up, p1 );
      vg_line( phys->rb.co, p0, 0xff00ff00 );
      vg_line( phys->rb.co, p1, 0xff000fff );

      if( fabsf(angle) < 0.999f )
      {
         v4f correction;
         q_axis_angle( correction, axis, acosf(angle)*4.0f*VG_TIMESTEP_FIXED );
         q_mul( correction, phys->rb.q, phys->rb.q );
      }


#endif

      float const DOWNFORCE = -k_downforce*VG_TIMESTEP_FIXED;
      v3_muladds( phys->rb.v, phys->rb.up, DOWNFORCE, phys->rb.v );

      player_physics_control();

      if( !phys->jump_charge && phys->jump > 0.2f )
      {
         v3f jumpdir;
         
         /* Launch more up if alignment is up else improve velocity */
         float aup = fabsf(v3_dot( (v3f){0.0f,1.0f,0.0f}, phys->rb.up )),
               mod = 0.5f,
               dir = mod + aup*(1.0f-mod);

         v3_copy( phys->rb.v, jumpdir );
         v3_normalize( jumpdir );
         v3_muls( jumpdir, 1.0f-dir, jumpdir );
         v3_muladds( jumpdir, phys->rb.up, dir, jumpdir );
         v3_normalize( jumpdir );
         
         float force = k_jump_force*phys->jump;
         v3_muladds( phys->rb.v, jumpdir, force, phys->rb.v );
         phys->jump = 0.0f;

         player.jump_time = vg.time;
         
         /* TODO: Move to audio file */
         audio_lock();
         audio_player_set_flags( &audio_player_extra, AUDIO_FLAG_SPACIAL_3D );
         audio_player_set_position( &audio_player_extra, phys->rb.co );
         audio_player_set_vol( &audio_player_extra, 20.0f );
         audio_player_playclip( &audio_player_extra, &audio_jumps[rand()%2] );
         audio_unlock();
      }
   }
   else
   {
      player_physics_control_air();
   }

   if( !phys->jump_charge )
   {
      phys->jump -= k_jump_charge_speed * VG_TIMESTEP_FIXED;
   }

   phys->jump_charge = 0;
   phys->jump = vg_clampf( phys->jump, 0.0f, 1.0f );
}

VG_STATIC void player_save_frame(void)
{
   player.phys_gate_frame = player.phys;
}

VG_STATIC void player_restore_frame(void)
{
   player.phys = player.phys_gate_frame;
   rb_update_transform( &player.phys.rb );
}

VG_STATIC void player_integrate(void)
{
   struct player_phys *phys = &player.phys;
   apply_gravity( phys->rb.v, VG_TIMESTEP_FIXED );
   v3_muladds( phys->rb.co, phys->rb.v, VG_TIMESTEP_FIXED, phys->rb.co );
}

VG_STATIC void player_do_motion(void)
{
   struct player_phys *phys = &player.phys;

   if( world.water.enabled )
   {
      if( (phys->rb.co[1] < 0.0f) && !player.is_dead )
      {
         audio_lock();
         audio_player_set_flags( &audio_player_extra, AUDIO_FLAG_SPACIAL_3D );
         audio_player_set_position( &audio_player_extra, phys->rb.co );
         audio_player_set_vol( &audio_player_extra, 20.0f );
         audio_player_playclip( &audio_player_extra, &audio_splash );
         audio_unlock();

         player_kill();
      }
   }


   v3f prevco;
   v3_copy( phys->rb.co, prevco );

   if( phys->on_board )
   {
      player_physics();
      player_integrate();
   }
   else
      player_walk_physics();
   
   
   /* Real angular velocity integration */
   v3_lerp( phys->rb.w, (v3f){0.0f,0.0f,0.0f}, 0.125f, phys->rb.w );
   if( v3_length2( phys->rb.w ) > 0.0f )
   {
      v4f rotation;
      v3f axis;
      v3_copy( phys->rb.w, axis );
      
      float mag = v3_length( axis );
      v3_divs( axis, mag, axis );
      q_axis_angle( rotation, axis, mag*k_rb_delta );
      q_mul( rotation, phys->rb.q, phys->rb.q );
   }

   /* Faux angular velocity */
   v4f rotate; 

   float lerpq = phys->in_air? 0.04f: 0.3f;
   phys->siY = vg_lerpf( phys->siY, phys->iY, lerpq );

   q_axis_angle( rotate, phys->rb.up, phys->siY );
   q_mul( rotate, phys->rb.q, phys->rb.q );
   phys->iY = 0.0f;

   /* 
    * Gate intersection, by tracing a line over the gate planes 
    */
   for( int i=0; i<world.gate_count; i++ )
   {
      struct route_gate *rg = &world.gates[i];
      teleport_gate *gate = &rg->gate;

      if( gate_intersect( gate, phys->rb.co, prevco ) )
      {
         m4x3_mulv( gate->transport, phys->rb.co, phys->rb.co );
         m3x3_mulv( gate->transport, phys->rb.v, phys->rb.v );
         m3x3_mulv( gate->transport, phys->vl, phys->vl );
         m3x3_mulv( gate->transport, phys->v_last, phys->v_last );
         m3x3_mulv( gate->transport, phys->m, phys->m );
         m3x3_mulv( gate->transport, phys->bob, phys->bob );

         v4f transport_rotation;
         m3x3_q( gate->transport, transport_rotation );
         q_mul( transport_rotation, phys->rb.q, phys->rb.q );
         
         world_routes_activate_gate( i );

         if( !phys->on_board )
         {
            v3f fwd_dir = {cosf(player.angles[0]),
                           0.0f,
                           sinf(player.angles[0])};
            m3x3_mulv( gate->transport, fwd_dir, fwd_dir );

            player.angles[0] = atan2f( fwd_dir[2], fwd_dir[0] );
         }
         
         player.rewind_length = 0;
         player.rewind_total_length = 0.0f;
         player.rewind_incrementer = 10000;
         player_save_frame();

         audio_lock();
         audio_play_oneshot( &audio_gate_pass, 1.0f );
         audio_unlock();
         break;
      }
   }
   
   rb_update_transform( &phys->rb );
}

VG_STATIC void player_freecam(void)
{
   player_mouseview();

   float movespeed = fc_speed;
   v3f lookdir = { 0.0f, 0.0f, -1.0f },
       sidedir = { 1.0f, 0.0f,  0.0f };
   
   m3x3_mulv( camera_mtx, lookdir, lookdir );
   m3x3_mulv( camera_mtx, sidedir, sidedir );
   
   static v3f move_vel = { 0.0f, 0.0f, 0.0f };
   if( vg_get_button( "forward" ) )
      v3_muladds( move_vel, lookdir, VG_TIMESTEP_FIXED * movespeed, move_vel );
   if( vg_get_button( "back" ) )
      v3_muladds( move_vel, lookdir, VG_TIMESTEP_FIXED *-movespeed, move_vel );
   if( vg_get_button( "left" ) )
      v3_muladds( move_vel, sidedir, VG_TIMESTEP_FIXED *-movespeed, move_vel );
   if( vg_get_button( "right" ) )
      v3_muladds( move_vel, sidedir, VG_TIMESTEP_FIXED * movespeed, move_vel );

   v3_muls( move_vel, 0.7f, move_vel );
   v3_add( move_vel, player.camera_pos, player.camera_pos );
}

VG_STATIC int reset_player( int argc, char const *argv[] )
{
   struct player_phys *phys = &player.phys;
   struct respawn_point *rp = NULL, *r;

   if( argc == 1 )
   {
      for( int i=0; i<world.spawn_count; i++ )
      {
         r = &world.spawns[i];
         if( !strcmp( r->name, argv[0] ) )
         {
            rp = r;
            break;
         }
      }

      if( !rp )
         vg_warn( "No spawn named '%s'\n", argv[0] );
   }

   if( !rp )
   {
      float min_dist = INFINITY;

      for( int i=0; i<world.spawn_count; i++ )
      {
         r = &world.spawns[i];
         float d = v3_dist2( r->co, phys->rb.co );
         
         vg_info( "Dist %s : %f\n", r->name, d );
         if( d < min_dist )
         {
            min_dist = d;
            rp = r;
         }
      }
   }

   if( !rp )
   {
      vg_error( "No spawn found\n" );
      if( !world.spawn_count )
         return 0;

      rp = &world.spawns[0];
   }

   player.is_dead = 0;

   m3x3f the_long_way;
   q_m3x3( rp->q, the_long_way );

   v3f delta = {1.0f,0.0f,0.0f};
   m3x3_mulv( the_long_way, delta, delta );

   player.angles[0] = atan2f( delta[0], -delta[2] ); 
   player.angles[1] = -asinf( delta[1] );


   v4_copy( rp->q, phys->rb.q );
   v3_copy( rp->co, phys->rb.co );
   v3_zero( phys->rb.v );
   
   phys->vswitch = 1.0f;
   phys->slip_last = 0.0f;
   phys->in_air = 1;
   phys->on_board = 0;
   m3x3_identity( phys->vr );

   player.mdl.shoes[0] = 1;
   player.mdl.shoes[1] = 1;
   
   rb_update_transform( &phys->rb );
   player_save_frame();
   return 1;
}

#endif /* PLAYER_PHYSICS_H */