sandsurf/glide basics

[carveJwlIkooP6JGAAIwe30JlM.git] / player_walk.c

#ifndef PLAYER_WALK_C
#define PLAYER_WALK_C

#include "player.h"
#include "input.h"
#include "audio.h"

static void player_walk_drop_in_vector( v3f vec ){
   v3f axis, init_dir;
   v3_cross( (v3f){0.0f,1.0f,0.0f}, player_walk.state.drop_in_normal, axis );
   v3_cross( axis, player_walk.state.drop_in_normal, init_dir );
   v3_normalize( init_dir );
   v3_muls( init_dir, 4.25f, vec );
}

static float player_xyspeed2(void){
   return v3_length2( (v3f){localplayer.rb.v[0], 0.0f, localplayer.rb.v[2]} );
}

static void player_walk_generic_to_skate( enum skate_activity init, f32 yaw ){
   localplayer.subsystem = k_player_subsystem_skate;

   v3f v;

   if( player_xyspeed2() < 0.1f * 0.1f )
      q_mulv( localplayer.rb.q, (v3f){0.0f,0.0f,1.6f}, v );
   else
      v3_copy( localplayer.rb.v, v );

   player_skate.state.activity_prev = k_skate_activity_ground;
   player_skate.state.activity = init;

   v3f dir;
   v3_copy( v, dir );
   v3_normalize( dir );

   q_axis_angle( localplayer.rb.q, (v3f){0.0f,1.0f,0.0f}, 
                 atan2f(-dir[0],-dir[2]) );
   q_normalize( localplayer.rb.q );

   q_mulv( localplayer.rb.q, (v3f){0.0f,1.0f,0.0f}, player_skate.state.cog );
   v3_add( player_skate.state.cog, localplayer.rb.co, player_skate.state.cog );

   v3_copy( v, player_skate.state.cog_v );
   v3_copy( v, localplayer.rb.v );

   player__begin_holdout( (v3f){0.0f,0.0f,0.0f} );
   player__skate_reset_animator();
   player__skate_clear_mechanics();
   rb_update_transform( &localplayer.rb );
   v3_copy( (v3f){yaw,0.0f,0.0f}, player_skate.state.trick_euler );

   if( init == k_skate_activity_air )
      player__approximate_best_trajectory();
}

static void player_walk_drop_in_to_skate(void){
   localplayer.immobile = 0;
   localplayer.subsystem = k_player_subsystem_skate;

   player_skate.state.activity_prev = k_skate_activity_ground;
   player_skate.state.activity = k_skate_activity_ground;

   player__begin_holdout( (v3f){0,0,0} );
   player__skate_clear_mechanics();
   player__skate_reset_animator();

   v3f init_velocity;
   player_walk_drop_in_vector( init_velocity );

   rb_update_transform( &localplayer.rb );
   v3_muladds( localplayer.rb.co, localplayer.rb.to_world[1], 1.0f, 
               player_skate.state.cog );
   v3_copy( init_velocity, player_skate.state.cog_v );
   v3_copy( init_velocity, localplayer.rb.v );
   v3_copy( init_velocity, localplayer.cam_control.cam_velocity_smooth );
   v3_copy( (v3f){player_walk.animator.board_yaw+1.0f,0,0}, 
            player_skate.state.trick_euler );
}

static void player_walk_drop_in_overhang_transform( f32 t, v3f co, v4f q ){
   v3f axis;
   v3_cross( (v3f){0,1,0}, player_walk.state.drop_in_normal, axis );
   v3_normalize( axis );

   float a = acosf( player_walk.state.drop_in_normal[1] ) * t;
   q_axis_angle( q, axis, a );

   float l = t * 0.5f,
         heading_angle = player_walk.state.drop_in_angle;

   v3f overhang;
   overhang[0] = sinf( heading_angle ) * l;
   overhang[1] = 0.28f * l;
   overhang[2] = cosf( heading_angle ) * l;

   q_mulv( q, overhang, overhang );
   v3_add( player_walk.state.drop_in_target, overhang, co );
}

static int player_walk_scan_for_drop_in(void){
   world_instance *world = world_current_instance();

   v3f dir, center;
   q_mulv( localplayer.rb.q, (v3f){0.0f,0.0f,1.0f}, dir );
   v3_muladds( localplayer.rb.co, localplayer.rb.to_world[1], -1.0f, center );

   ray_hit samples[20];
   int sample_count = 0;

   for( int i=0; i<20; i ++ ){
      float t = (float)i * (1.0f/19.0f),
            s = sinf( t * VG_PIf * 0.25f ),
            c = cosf( t * VG_PIf * 0.25f );

      v3f ray_dir, pos;
      v3_muls   ( localplayer.rb.to_world[1], -c, ray_dir );
      v3_muladds( ray_dir, dir, -s, ray_dir );
      v3_muladds( center, ray_dir, -2.0f, pos );

      ray_hit *ray = &samples[ sample_count ];
      ray->dist = 2.0f;

      if( ray_world( world, pos, ray_dir, ray, 0 ) ){
         vg_line( pos, ray->pos, VG__RED );
         vg_line_point( ray->pos, 0.025f, VG__BLACK );
         
         sample_count ++;
      }
   }

   float min_a = 0.70710678118654752f;
   ray_hit *candidate = NULL;

   if( sample_count >= 2 ){
      for( int i=0; i<sample_count-1; i++ ){
         ray_hit *s0 = &samples[i],
                 *s1 = &samples[i+1];

         float a = v3_dot( s0->normal, s1->normal );

         if( (a < min_a) && (a >= -0.1f) && (s0->normal[1]>s1->normal[1]) ){
            min_a = a;
            candidate = s0;
         }
      }
   }

   if( candidate ){
      v4f pa, pb, pc;
      
      ray_hit *s0 = candidate,
              *s1 = candidate+1;

      vg_line( s0->pos, s1->pos, VG__WHITE );

      v3_copy( s0->normal, pa );
      v3_copy( s1->normal, pb );
      v3_cross( localplayer.rb.to_world[1], dir, pc );
      v3_normalize( pc );

      pa[3] = v3_dot( pa, s0->pos );
      pb[3] = v3_dot( pb, s1->pos );
      pc[3] = v3_dot( pc, localplayer.rb.co );

      v3f edge;
      if( plane_intersect3( pa, pb, pc, edge ) ){
         v3_copy( edge, player_walk.state.drop_in_target );
         v3_copy( s1->normal, player_walk.state.drop_in_normal );
         v3_copy( localplayer.rb.co, player_walk.state.drop_in_start );

         player_walk.state.drop_in_start_angle = player_get_heading_yaw();
         player_walk.state.drop_in_angle = 
            atan2f( player_walk.state.drop_in_normal[0],
                    player_walk.state.drop_in_normal[2] );

         /* TODO: scan multiple of these? */
         v3f oco;
         v4f oq;
         player_walk_drop_in_overhang_transform( 1.0f, oco, oq );

         v3f va = {0.0f,0.0f,-k_board_length - 0.3f},
             vb = {0.0f,0.0f, k_board_length + 0.3f};

         q_mulv( oq, va, va );
         q_mulv( oq, vb, vb );
         v3_add( oco, va, va );
         v3_add( oco, vb, vb );

         v3f v0;
         v3_sub( vb, va, v0 );
         v3_normalize( v0 );

         ray_hit ray;
         ray.dist = k_board_length*2.0f + 0.6f;
         
         if( ray_world( world, va, v0, &ray, 0 ) ){
            vg_line( va, vb, VG__RED );
            vg_line_point( ray.pos, 0.1f, VG__RED );
            vg_error( "invalidated\n" );
            return 0;
         }

         v3_muls( v0, -1.0f, v0 );
         if( ray_world( world, vb, v0, &ray, 0 ) ){
            vg_line( va, vb, VG__RED );
            vg_line_point( ray.pos, 0.1f, VG__RED );
            vg_error( "invalidated\n" );
            return 0;
         }

         player_walk_drop_in_vector( localplayer.rb.v );
         return 1;
      }
      else{
         vg_error( "failed to find intersection of drop in\n" );
      }
   }

   return 0;
}

static bool player__preupdate_anim( struct skeleton_anim *anim, f32 *t, 
                                    f32 speed ){
   f32 length = (f32)(anim->length-1) / anim->rate;
   *t += (vg.time_delta * speed) / length;

   if( *t >= 1.0f ) return 1;
   else             return 0;
}

static void player_walk_pre_sit(void){
   struct player_walk *w = &player_walk;

   v2f steer;
   joystick_state( k_srjoystick_steer, steer );

   vg_slewf( &w->state.transition_t, 1.0f, vg.time_delta );

   if( button_down(k_srbind_sit) || (v2_length2(steer)>0.2f) ||
       button_down(k_srbind_jump) ){
      w->state.activity = k_walk_activity_sit_up;
   }
   return;
}

static void player_walk_pre_sit_up(void){
   struct player_walk *w = &player_walk;
   
   if( w->state.transition_t > 0.0f )
      vg_slewf( &w->state.transition_t, 0.0f, vg.time_delta );
   else 
      w->state.activity = k_walk_activity_ground;

   if( button_down(k_srbind_sit) )
      w->state.activity = k_walk_activity_sit;

   return;
}

static void player_walk_pre_ground(void){
   struct player_walk *w = &player_walk;

   if( button_down(k_srbind_sit) ){
      v3_zero( localplayer.rb.v );
      w->state.activity = k_walk_activity_sit;
      w->state.transition_t = 0.0f;
      return;
   }

   if( button_down( k_srbind_use ) ){
      if( player_walk_scan_for_drop_in() ){
         w->state.activity = k_walk_activity_odrop_in;
      }
      else{
         w->state.activity = k_walk_activity_oregular;
      }

      w->state.transition_t = 0.0f;
   }

   if( button_down( k_srbind_jump ) ){
      w->state.jump_queued = 1;
      w->state.jump_input_time = vg.time;
   }
}

static void player_walk_pre_air(void){
   struct player_walk *w = &player_walk;
   if( button_down( k_srbind_use ) ){
      w->state.activity = k_walk_activity_oair;
      w->state.transition_t = 0.0f;
   }

   if( button_down( k_srbind_jump ) ){
      w->state.jump_queued = 1;
      w->state.jump_input_time = vg.time;
   }
}

static void player_walk_pre_drop_in(void){
   struct player_walk *w = &player_walk;
   bool finished = player__preupdate_anim( w->anim_drop_in, 
                                          &w->state.transition_t, 1.0f );
   if( finished )
      player_walk_drop_in_to_skate();
}

static void player_walk_pre_caveman(void){
   struct player_walk *w = &player_walk;
   bool finished = player__preupdate_anim( w->anim_jump_to_air,
                                          &w->state.transition_t, 1.0f );
   if( finished ){
      player_walk_generic_to_skate( k_skate_activity_air, 
                                    player_walk.animator.board_yaw );
   }
}

static void player_walk_pre_running_start(void){
   struct player_walk *w = &player_walk;
   bool finished = player__preupdate_anim( w->anim_intro, 
                                          &w->state.transition_t, 1.0f );
   if( finished ){
      /* TODO: get the derivative of the last keyframes to calculate new
       * velocity for player */
      player_walk_generic_to_skate( k_skate_activity_ground, 
                                    player_walk.animator.board_yaw+1.0f );
   }
}

static void player_walk_pre_popoff(void){
   struct player_walk *w = &player_walk;
   bool finished = player__preupdate_anim( w->anim_popoff, 
                                          &w->state.transition_t, 1.0f );

   if( finished ){
      w->state.activity = k_walk_activity_ground;
      w->animator.board_yaw += 1.0f;
   }
}

static void player__walk_pre_update(void){
   struct player_walk *w = &player_walk;

   if( localplayer.immobile ) return;
   else player_look( localplayer.angles, skaterift.time_rate );

   enum walk_activity a = w->state.activity;

   if     ( a == k_walk_activity_sit )       player_walk_pre_sit();
   else if( a == k_walk_activity_sit_up )    player_walk_pre_sit_up();
   else if( a == k_walk_activity_ground )    player_walk_pre_ground();
   else if( a == k_walk_activity_air )       player_walk_pre_air();
   else if( a == k_walk_activity_odrop_in )  player_walk_pre_drop_in();
   else if( a == k_walk_activity_oair )      player_walk_pre_caveman();
   else if( a == k_walk_activity_oregular )  player_walk_pre_running_start();
   else if( a == k_walk_activity_ipopoff )   player_walk_pre_popoff();
}

static int player_walk_normal_standable( v3f n ){
   return n[1] > 0.70710678118f;
}

static void player_accelerate( v3f v, v3f movedir, f32 speed, f32 accel ){
   float currentspeed = v3_dot( v, movedir ),
         addspeed     = speed - currentspeed;

   if( addspeed <= 0 )
      return;

   float accelspeed = accel * k_rb_delta * speed;

   if( accelspeed > addspeed )
      accelspeed = addspeed;

   v3_muladds( v, movedir, accelspeed, v );
}

static void player_friction( v3f v, f32 friction ){
   float speed = v3_length( v ),
         drop  = 0.0f,
         control = vg_maxf( speed, k_stopspeed );

   if( speed < 0.04f )
      return;

   drop += control * friction * k_rb_delta;

   float newspeed = vg_maxf( 0.0f, speed - drop );
   newspeed /= speed;

   v3_muls( v, newspeed, v );
}

static void player_walk_custom_filter( world_instance *world,
                                          rb_ct *man, int len, f32 w ){
   for( int i=0; i<len; i++ ){
      rb_ct *ci = &man[i];
      if( ci->type == k_contact_type_disabled ||
          ci->type == k_contact_type_edge ) 
         continue;


      float d1 = v3_dot( ci->co, ci->n );

      for( int j=0; j<len; j++ ){
         if( j == i )
            continue;

         rb_ct *cj = &man[j];
         if( cj->type == k_contact_type_disabled ) 
            continue;

         struct world_surface *si = world_contact_surface( world, ci ),
                              *sj = world_contact_surface( world, cj );

         if(  (sj->info.flags & k_material_flag_walking) &&
             !(si->info.flags & k_material_flag_walking)){
            continue;
         }
         
         float d2 = v3_dot( cj->co, ci->n ),
               d  = d2-d1;

         if( fabsf( d ) <= w ){
            cj->type = k_contact_type_disabled;
         }
      }
   }
}

static void player_walk_update_generic(void){
   struct player_walk *w = &player_walk;

   if( (w->state.activity != k_walk_activity_oregular) &&
       (w->state.activity != k_walk_activity_oair) ){
      joystick_state( k_srjoystick_steer, w->state.steer );
      w->state.steer[2] = button_press(k_srbind_run)? k_runspeed: k_walkspeed;
      if( v2_length2(w->state.steer)>1.0f )
         v2_normalize(w->state.steer);
   }

   v3_copy( localplayer.rb.co, w->state.prev_pos );
   v3_zero( localplayer.rb.w );

   world_instance *world = world_current_instance();

   if( world->water.enabled ){
      if( localplayer.rb.co[1]+0.4f < world->water.height ){
         player__networked_sfx( k_player_subsystem_walk, 32, 
                                k_player_walk_soundeffect_splash,
                                localplayer.rb.co, 1.0f );
         player__dead_transition( k_player_die_type_generic );
         return;
      }
   }

   enum walk_activity prev_state = w->state.activity;

   w->collider.height = 2.0f;
   w->collider.radius = 0.3f;

   m4x3f mtx;
   m3x3_copy( localplayer.rb.to_world, mtx );
   v3_add( localplayer.rb.co, (v3f){0,1,0}, mtx[3] );

   vg_line_capsule( mtx, w->collider.radius, w->collider.height, VG__WHITE );

   rb_ct manifold[64];
   int len;

   float yaw = localplayer.angles[0];

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

   /* 
    * Collision detection
    */

   len = rb_capsule__scene( mtx, &w->collider, NULL, 
                            &world->rb_geo.inf.scene, manifold, 0 );
   player_walk_custom_filter( world, manifold, len, 0.01f );
   len = rb_manifold_apply_filtered( manifold, len );

   v3f surface_avg = { 0.0f, 0.0f, 0.0f };

   w->state.activity = k_walk_activity_air;
   w->surface = k_surface_prop_concrete;

   for( int i=0; i<len; i++ ){
      struct contact *ct = &manifold[i];
      rb_debug_contact( ct );

      if( player_walk_normal_standable( ct->n ) ){
         w->state.activity = k_walk_activity_ground;

         v3_add( surface_avg, ct->n, surface_avg );

         struct world_surface *surf = world_contact_surface( world, ct );
         if( surf->info.surface_prop > w->surface )
            w->surface = surf->info.surface_prop;
      }

      rb_prepare_contact( ct, k_rb_delta );
   }

   /* 
    * Move & Friction
    */
   float accel_speed = 0.0f, nominal_speed = 0.0f;
   v3f movedir;

   v3_muls( right_dir, w->state.steer[0], movedir );
   v3_muladds( movedir, forward_dir, w->state.steer[1], movedir );

   if( w->state.activity == k_walk_activity_ground ){
      v3_normalize( surface_avg );

      v3f tx, ty;
      v3_tangent_basis( surface_avg, tx, ty );

      if( v2_length2(w->state.steer) > 0.001f ){
         /* clip movement to the surface */
         float d = v3_dot(surface_avg,movedir);
         v3_muladds( movedir, surface_avg, -d, movedir );
      }

      accel_speed = k_walk_accel;
      nominal_speed = w->state.steer[2];

      /* jump */
      if( w->state.jump_queued ){
         w->state.jump_queued = 0;

         f32 t = vg.time - w->state.jump_input_time;
         if( t < PLAYER_JUMP_EPSILON ){
            localplayer.rb.v[1] = 5.0f;
            w->state.activity = k_walk_activity_air;
            prev_state = k_walk_activity_air;
            accel_speed = k_walk_air_accel;
            nominal_speed = k_airspeed;
         }
      }
      else{
         player_friction( localplayer.rb.v, k_walk_friction );
      }
   }
   else{
      accel_speed = k_walk_air_accel;
      nominal_speed = k_airspeed;
   }

   if( v2_length2( w->state.steer ) > 0.001f ){
      player_accelerate( localplayer.rb.v, movedir, 
                         nominal_speed, accel_speed );
      v3_normalize( movedir );
   }
   
   /*
    * Resolve velocity constraints
    */
   for( int j=0; j<5; j++ ){
      for( int i=0; i<len; i++ ){
         struct contact *ct = &manifold[i];
         
         /*normal */
         float vn = -v3_dot( localplayer.rb.v, ct->n );

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

         v3_muladds( localplayer.rb.v, ct->n, vn, localplayer.rb.v );
      }
   }

   /* stepping */
   if( w->state.activity == k_walk_activity_ground||
       prev_state == k_walk_activity_ground ){
      float max_dist = 0.4f;

      v3f pa, pb;
      v3_copy( localplayer.rb.co, pa );
      pa[1] += w->collider.radius + max_dist;
      v3_add( pa, (v3f){0, -max_dist * 2.0f, 0}, pb );
      vg_line( pa, pb, 0xff000000 );

      v3f n;
      float t;
      if( spherecast_world( world, pa, pb, 
                            w->collider.radius, &t, n, 0 ) != -1 ){
         if( player_walk_normal_standable(n) ){
            v3_lerp( pa, pb, t, localplayer.rb.co );
            localplayer.rb.co[1] += -w->collider.radius - k_penetration_slop;
            w->state.activity = k_walk_activity_ground;

            float d = -v3_dot(n,localplayer.rb.v);
            v3_muladds( localplayer.rb.v, n, d, localplayer.rb.v );
            localplayer.rb.v[1] += -k_gravity * k_rb_delta;
         }
      }
   }

   /* 
    * Depenetrate
    */
   v3f dt;
   rb_depenetrate( manifold, len, dt );
   v3_add( dt, localplayer.rb.co, localplayer.rb.co );

   /* integrate */
   if( w->state.activity == k_walk_activity_air ){
      localplayer.rb.v[1] += -k_gravity*k_rb_delta;
   }

   if( localplayer.immobile ){
      localplayer.rb.v[0] = 0.0f;
      localplayer.rb.v[2] = 0.0f;
   }

   v3_muladds( localplayer.rb.co, localplayer.rb.v, k_rb_delta, 
               localplayer.rb.co );
   v3_add( localplayer.rb.co, (v3f){0,1,0}, mtx[3] );
   vg_line_capsule( mtx, w->collider.radius, w->collider.height, VG__GREEN );

   /* 
    * CCD routine 
    * ---------------------------------------------------
    *
    */
   v3f lwr_prev,
       lwr_now,
       lwr_offs = { 0.0f, w->collider.radius, 0.0f };

   v3_add( lwr_offs, w->state.prev_pos, lwr_prev );
   v3_add( lwr_offs, localplayer.rb.co, lwr_now );

   v3f movedelta;
   v3_sub( localplayer.rb.co, w->state.prev_pos, movedelta );

   float movedist = v3_length( movedelta );

   if( movedist > 0.3f ){
      float t, sr = w->collider.radius-0.04f;
      v3f n;

      if( spherecast_world( world, lwr_prev, lwr_now, sr, &t, n, 0 ) != -1 ){
         v3_lerp( lwr_prev, lwr_now, vg_maxf(0.01f,t), localplayer.rb.co );
         localplayer.rb.co[1] -= w->collider.radius;
         rb_update_transform( &localplayer.rb );

         v3_add( localplayer.rb.co, (v3f){0,1,0}, mtx[3] );
         vg_line_capsule( mtx, w->collider.radius, w->collider.height, VG__RED);
      }
   }

   u32 id = world_intersect_gates(world, localplayer.rb.co, w->state.prev_pos);
   if( id ){
      ent_gate *gate = mdl_arritm( &world->ent_gate, mdl_entity_id_id(id) );
      m4x3_mulv( gate->transport, localplayer.rb.co, localplayer.rb.co );
      m3x3_mulv( gate->transport, localplayer.rb.v,  localplayer.rb.v );

      v4f transport_rotation;
      m3x3_q( gate->transport, transport_rotation );
      q_mul( transport_rotation, localplayer.rb.q, localplayer.rb.q );

      rb_update_transform( &localplayer.rb );
      player__pass_gate( id );
   }
   rb_update_transform( &localplayer.rb );

   if( (prev_state == k_walk_activity_oregular) ||
       (prev_state == k_walk_activity_oair) ||
       (prev_state == k_walk_activity_ipopoff) ){
      w->state.activity = prev_state;
   }

   w->move_speed = vg_minf( v2_length( (v2f){ localplayer.rb.v[0], 
                                              localplayer.rb.v[2] } ),
                            k_runspeed );
}

static void player__walk_post_update(void){
   struct player_walk *w = &player_walk;

   m4x3f mtx;
   m3x3_copy( localplayer.rb.to_world, mtx );
   v3_add( localplayer.rb.co, (v3f){0,1,0}, mtx[3] );

   float substep = vg.time_fixed_extrapolate;
   v3_muladds( mtx[3], localplayer.rb.v, k_rb_delta*substep, mtx[3] );
   vg_line_capsule( mtx, w->collider.radius, w->collider.height, VG__YELOW );

   /* Calculate header */
   v3f v;
   if( (player_xyspeed2() > 0.1f*0.1f) ){
      f32 r = 0.3f;
      if( (w->state.activity == k_walk_activity_ground) ||
          (w->state.activity == k_walk_activity_ipopoff) ||
          (w->state.activity == k_walk_activity_oregular) ){
         r = 0.07f;
      }

      f32 ta = atan2f( localplayer.rb.v[0], localplayer.rb.v[2] );
      v4f qt;
      q_axis_angle( qt, (v3f){0,1,0}, ta );
      q_nlerp( localplayer.rb.q, qt, vg.time_delta/r, localplayer.rb.q );
   }

   vg_line_point( w->state.drop_in_target, 0.1f, VG__GREEN );
   v3f p1;
   v3_muladds( w->state.drop_in_target, w->state.drop_in_normal, 0.3f, p1 );
   vg_line( w->state.drop_in_target, p1, VG__GREEN );
   v3_muladds( w->state.drop_in_target, localplayer.rb.to_world[1], 0.3f, p1 );
   vg_line( w->state.drop_in_target, p1, VG__GREEN );

   float a = player_get_heading_yaw();
   p1[0] = sinf( a );
   p1[1] = 0.0f;
   p1[2] = cosf( a );

   v3_add( localplayer.rb.co, p1, p1 );
   vg_line( localplayer.rb.co, p1, VG__PINK );

   int walk_phase = 0;
   if( vg_fractf(w->state.walk_timer) > 0.5f )
      walk_phase = 1;
   else
      walk_phase = 0;

   if( (w->state.step_phase != walk_phase) && 
       (w->state.activity == k_walk_activity_ground ) )
   {
      audio_lock();
      if( w->surface == k_surface_prop_concrete ){
         audio_oneshot_3d( 
               &audio_footsteps[vg_randu32(&vg.rand) % 
                                 vg_list_size(audio_footsteps)], 
               localplayer.rb.co, 40.0f, 1.0f 
         );
      }
      else if( w->surface == k_surface_prop_grass ){
         audio_oneshot_3d( 
           &audio_footsteps_grass[ vg_randu32(&vg.rand) %
                                    vg_list_size(audio_footsteps_grass)],
            localplayer.rb.co, 40.0f, 1.0f 
         );
      }
      else if( w->surface == k_surface_prop_wood ){
         audio_oneshot_3d( 
           &audio_footsteps_wood[ vg_randu32(&vg.rand) %
                                    vg_list_size(audio_footsteps_wood)],
            localplayer.rb.co, 40.0f, 1.0f 
         );
      }
      audio_unlock();
   }

   w->state.step_phase = walk_phase;
}

static void player__walk_update(void){
   struct player_walk *w = &player_walk;

   if( (w->state.activity == k_walk_activity_air) ||
       (w->state.activity == k_walk_activity_ground) ||
       (w->state.activity == k_walk_activity_oair) ||
       (w->state.activity == k_walk_activity_oregular) ||
       (w->state.activity == k_walk_activity_ipopoff) ){
      player_walk_update_generic();
   }
}

static void player_walk_animate_drop_in(void){
   struct player_walk *w = &player_walk;
   struct player_walk_animator *animator = &w->animator;
   struct skeleton_anim *anim = w->anim_drop_in;

   f32 length = (f32)(anim->length-1) / anim->rate,
       time   = w->state.transition_t;

   f32 walk_yaw = vg_alerpf( w->state.drop_in_start_angle, 
                             w->state.drop_in_angle, animator->transition_t );
   v3_lerp( w->state.drop_in_start, w->state.drop_in_target,
            animator->transition_t, localplayer.rb.co );

   q_axis_angle( localplayer.rb.q, (v3f){0,1,0}, walk_yaw + VG_PIf );

   /* the drop in bit */
   v3f final_co;
   v4f final_q;
   player_walk_drop_in_overhang_transform( animator->transition_t, 
                                           final_co, final_q );

   q_mul( final_q, localplayer.rb.q, localplayer.rb.q );
   v3_lerp( localplayer.rb.co, final_co, animator->transition_t, 
            localplayer.rb.co );

   rb_update_transform( &localplayer.rb );

   v3_muladds( localplayer.rb.co, localplayer.rb.to_world[1], 
               -0.1f*animator->transition_t, localplayer.rb.co );

   v3_copy( localplayer.rb.co, animator->root_co );
   v4_copy( localplayer.rb.q, animator->root_q );

   /* for the camera purposes only */
   v3f init_velocity;
   player_walk_drop_in_vector( init_velocity );
   v3_muls( init_velocity, animator->transition_t, localplayer.rb.v );
   v3_copy( localplayer.rb.v, 
            localplayer.cam_control.cam_velocity_smooth );
}

static void player_walk_animate_generic(void){
   struct player_walk *w = &player_walk;
   struct player_walk_animator *animator = &w->animator;

   v4f _null;
   rb_extrapolate( &localplayer.rb, animator->root_co, _null );

   f32 walk_yaw = player_get_heading_yaw(),
       head_yaw = localplayer.angles[0] + VG_PIf,
       y = vg_angle_diff( head_yaw, -walk_yaw ),
       p = vg_clampf( localplayer.angles[1], 
                        -k_sit_pitch_limit, k_sit_pitch_limit );

   if( fabsf(y) > k_sit_yaw_limit ){
      y = 0.0f;
      p = 0.0f;
   }

   animator->yaw = vg_lerpf( animator->yaw, y, vg.time_delta*2.0f );
   animator->pitch = vg_lerpf( animator->pitch, p, vg.time_delta*2.8f );
   q_axis_angle( animator->root_q, (v3f){0,1,0}, walk_yaw + VG_PIf );

   v4f qrev;
   q_axis_angle( qrev, (v3f){0,1,0}, VG_TAUf*0.5f );
   q_mul( localplayer.rb.q, qrev, animator->root_q );
}

static void player__walk_animate(void){
   struct player_walk *w = &player_walk;
   player_pose *pose = &localplayer.pose;
   struct player_walk_animator *animator = &w->animator;

   animator->activity = w->state.activity;
   animator->transition_t = w->state.transition_t;

   {
      f32 fly = (w->state.activity == k_walk_activity_air)? 1.0f: 0.0f, 
          rate;

      if( w->state.activity == k_walk_activity_air ) rate = 2.4f;
      else rate = 9.0f;

      animator->fly = vg_lerpf( animator->fly, fly, rate*vg.time_delta );
      animator->run = vg_lerpf( animator->run, w->move_speed, 
                                8.0f*vg.time_delta);
   }

   if( animator->run > 0.025f ){
      f32 walk_norm = 30.0f/(float)w->anim_walk->length,
          run_norm  = 30.0f/(float)w->anim_run->length,
          l;

      if( animator->run <= k_walkspeed )
         l = (animator->run / k_walkspeed) * walk_norm;
      else {
         l = vg_lerpf( walk_norm, run_norm, 
                      (animator->run-k_walkspeed) / (k_runspeed-k_walkspeed) );
      }
      w->state.walk_timer += l * vg.time_delta;
   }
   else
      w->state.walk_timer = 0.0f;

   animator->walk_timer = w->state.walk_timer;

   player_walk_animate_generic();
   if( w->state.activity == k_walk_activity_odrop_in ){
      player_walk_animate_drop_in();
   }

   if( (w->state.activity == k_walk_activity_odrop_in) ||
       (w->state.activity == k_walk_activity_oregular) ||
       (w->state.activity == k_walk_activity_oair) ){
      localplayer.cam_velocity_influence = w->animator.transition_t;
   }
   else if( w->state.activity == k_walk_activity_ipopoff ){
      localplayer.cam_velocity_influence = 1.0f-w->animator.transition_t;
   }
   else
      localplayer.cam_velocity_influence = 0.0f;
}

static void player_walk_pose_sit( struct player_walk_animator *animator,
                                  player_pose *pose ){
   mdl_keyframe bpose[32];

   struct player_walk *w = &player_walk;
   struct skeleton *sk = &localplayer.skeleton;

   f32 t  = animator->transition_t,
       st = t * ((f32)(w->anim_sit->length-1)/30.0f);
   skeleton_sample_anim( sk, w->anim_sit, st, bpose );

   v4f qy,qp;
   f32 *qh = bpose[localplayer.id_head-1].q;
   q_axis_angle( qy, (v3f){0,1,0}, animator->yaw*0.5f*t );
   q_axis_angle( qp, (v3f){0,0,1}, animator->pitch*t );
   q_mul( qy, qh, qh );
   q_mul( qh, qp, qh );
   q_normalize( qh );

   qh = bpose[localplayer.id_chest-1].q;
   q_axis_angle( qy, (v3f){0,1,0}, animator->yaw*0.5f*t );
   q_mul( qy, qh, qh );
   q_normalize( qh );

   skeleton_lerp_pose( sk, pose->keyframes, bpose, 
                       vg_minf(1.0f,t*10.0f), pose->keyframes );
}

enum walk_transition_type {
   k_walk_transition_in,
   k_walk_transition_out,
   k_walk_transition_outin,
};

static void player_walk_pose_transition( 
      struct player_walk_animator *animator, struct skeleton_anim *anim,
      enum walk_transition_type type,
      mdl_keyframe apose[32], f32 *mask, player_pose *pose ){

   mdl_keyframe bpose[32];

   struct player_walk *w = &player_walk;
   struct skeleton *sk = &localplayer.skeleton;
   
   f32 length   = (f32)(anim->length-1) / anim->rate,
       t        = animator->transition_t * length,
       blend    = 1.0f;

   if( type == k_walk_transition_in || type == k_walk_transition_outin )
      blend = vg_minf( blend, length-t );

   if( type == k_walk_transition_out || type == k_walk_transition_outin )
      blend = vg_minf( blend, t );

   blend = vg_smoothstepf( vg_minf(1,blend/k_anim_transition) );

   skeleton_sample_anim_clamped( sk, anim, t, bpose );

   mdl_keyframe *kf_board = &bpose[localplayer.id_board-1];
   f32 yaw = animator->board_yaw * VG_TAUf * 0.5f;

   v4f qyaw;
   q_axis_angle( qyaw, (v3f){0,1,0}, yaw );
   q_mul( kf_board->q, qyaw, kf_board->q );
   q_normalize( kf_board->q );

   if( mask ){
      for( i32 i=0; i<sk->bone_count-1; i ++ )
         keyframe_lerp( apose+i, bpose+i, blend*mask[i], pose->keyframes+i );
   }
   else
      skeleton_lerp_pose( sk, apose, bpose, blend, pose->keyframes );
}

static void player__walk_pose( void *_animator, player_pose *pose ){
   struct player_walk *w = &player_walk;
   struct player_walk_animator *animator = _animator;
   struct skeleton *sk = &localplayer.skeleton;

   v3_copy( animator->root_co, pose->root_co );
   v4_copy( animator->root_q, pose->root_q );
   pose->board.lean = 0.0f;
   pose->type = k_player_pose_type_ik;

   float walk_norm = (float)w->anim_walk->length/30.0f,
         run_norm  = (float)w->anim_run->length/30.0f,
         t = animator->walk_timer;

   /* walk/run */
   mdl_keyframe apose[32], bpose[32];
   if( animator->run <= k_walkspeed ){ 
      /* walk / idle */
      f32 l = vg_minf( 1, (animator->run/k_walkspeed)*6.0f );
      skeleton_sample_anim( sk, w->anim_idle, vg.time*0.1f, apose );
      skeleton_sample_anim( sk, w->anim_walk, t*walk_norm, bpose );
      skeleton_lerp_pose( sk, apose, bpose, l, apose );
   }
   else { 
      /* walk / run */
      f32 l = (animator->run-k_walkspeed) / (k_runspeed-k_walkspeed);
      skeleton_sample_anim( sk, w->anim_walk, t*walk_norm, apose );
      skeleton_sample_anim( sk, w->anim_run, t*run_norm, bpose );
      skeleton_lerp_pose( sk, apose, bpose, l, apose );
   }

   /* air */
   skeleton_sample_anim( sk, w->anim_jump, vg.time*0.6f, bpose );
   skeleton_lerp_pose( sk, apose, bpose, animator->fly, apose );

   mdl_keyframe *kf_board = &apose[localplayer.id_board-1];
   f32 yaw = animator->board_yaw;

   if( animator->activity == k_walk_activity_ipopoff )
      if( animator->transition_t > 0.5f )
         yaw += 1.0f;

   v4f qyaw;
   q_axis_angle( qyaw, (v3f){0,1,0}, yaw * VG_TAUf * 0.5f );
   q_mul( kf_board->q, qyaw, kf_board->q );
   q_normalize( kf_board->q );

   /* sit */
   if( (animator->activity == k_walk_activity_sit) ||
       (animator->activity == k_walk_activity_sit_up) ){
      player_walk_pose_sit( animator, pose );
   }
   else if( animator->activity == k_walk_activity_odrop_in ){
      player_walk_pose_transition( 
            animator, w->anim_drop_in, k_walk_transition_out, apose, 
            NULL, pose );
   }
   else if( animator->activity == k_walk_activity_oair ){
      player_walk_pose_transition(
            animator, w->anim_jump_to_air, k_walk_transition_out, apose, 
            NULL, pose );
   }
   else if( animator->activity == k_walk_activity_oregular ){
      player_walk_pose_transition( 
            animator, w->anim_intro, k_walk_transition_out, apose, 
            NULL, pose );
   }
   else if( animator->activity == k_walk_activity_ipopoff ){
      if( animator->run > 0.2f ){
         f32 t = 1.0f-vg_minf( animator->run-0.2f, 1.0f ),
             mask[ 32 ];

         for( u32 i=0; i<32; i ++ ) 
            mask[i] = 1.0f;

         mask[ localplayer.id_ik_foot_l-1 ] = t;
         mask[ localplayer.id_ik_foot_r-1 ] = t;
         mask[ localplayer.id_ik_knee_l-1 ] = t;
         mask[ localplayer.id_ik_knee_r-1 ] = t;
         mask[ localplayer.id_hip-1 ] = t;
         player_walk_pose_transition( 
               animator, w->anim_popoff, k_walk_transition_in, apose,
               mask, pose );
      }
      else{
         player_walk_pose_transition( 
               animator, w->anim_popoff, k_walk_transition_in, apose,
               NULL, pose );
      }
   }
   else {
      skeleton_copy_pose( sk, apose, pose->keyframes );
   }
}

static void player__walk_post_animate(void){
   /* 
    * Camera 
    */
   struct player_walk *w = &player_walk;

}

static void player__walk_im_gui(void){
   struct player_walk *w = &player_walk;
   player__debugtext( 1, "V:  %5.2f %5.2f %5.2f (%5.2fm/s)",
      localplayer.rb.v[0], localplayer.rb.v[1], localplayer.rb.v[2],
      v3_length(localplayer.rb.v) );
   player__debugtext( 1, "CO: %5.2f %5.2f %5.2f",localplayer.rb.co[0],
                                                 localplayer.rb.co[1],
                                                 localplayer.rb.co[2] );
   player__debugtext( 1, "transition: %5.2f ", w->state.transition_t );
   player__debugtext( 1, "activity: %s\n",
                           (const char *[]){ "air",
                                             "ground",
                                             "sit",
                                             "sit_up",
                                             "inone",
                                             "ipopoff",
                                             "oair",
                                             "odrop_in",
                                             "oregular" }
                                             [w->state.activity] );
   player__debugtext( 1, "surface: %s\n",
                           (const char *[]){ "concrete",
                                             "wood",
                                             "grass",
                                             "tiles",
                                             "metal",
                                             "snow",
                                             "sand" }
                                             [w->surface] );
}

static void player__walk_bind(void){
   struct player_walk *w = &player_walk;
   struct skeleton *sk = &localplayer.skeleton;

   w->anim_idle         = skeleton_get_anim( sk, "idle_cycle+y" );
   w->anim_walk         = skeleton_get_anim( sk, "walk+y" );
   w->anim_run          = skeleton_get_anim( sk, "run+y" );
   w->anim_jump         = skeleton_get_anim( sk, "jump+y" );
   w->anim_jump_to_air  = skeleton_get_anim( sk, "jump_to_air" );
   w->anim_drop_in      = skeleton_get_anim( sk, "drop_in" );
   w->anim_intro        = skeleton_get_anim( sk, "into_skate" );
   w->anim_sit          = skeleton_get_anim( sk, "sit" );
   w->anim_popoff       = skeleton_get_anim( sk, "pop_off_short" );
}

static void player__walk_transition( bool grounded, f32 board_yaw ){
   struct player_walk *w = &player_walk;
   w->state.activity = k_walk_activity_air;

   if( grounded ){
      w->state.activity = k_walk_activity_ipopoff;
   }

   w->state.transition_t = 0.0f;
   w->state.jump_queued = 0;
   w->state.jump_input_time = 0.0;
   w->state.walk_timer = 0.0f;
   w->state.step_phase = 0;
   w->animator.board_yaw = fmodf( board_yaw, 2.0f );
   rb_update_transform( &localplayer.rb );
}

static void player__walk_reset(void){
   struct player_walk *w = &player_walk;
   w->state.activity = k_walk_activity_air;
   w->state.transition_t = 0.0f;

   v3f fwd = { 0.0f, 0.0f, 1.0f };
   q_mulv( localplayer.rb.q, fwd, fwd );
   q_axis_angle( localplayer.rb.q, (v3f){0.0f,1.0f,0.0f}, 
                 atan2f(fwd[0], fwd[2]) );

   rb_update_transform( &localplayer.rb );
}

static void player__walk_animator_exchange( bitpack_ctx *ctx, void *data ){
   struct player_walk_animator *animator = data;

   bitpack_qv3f( ctx, 24, -1024.0f, 1024.0f, animator->root_co );
   bitpack_qquat( ctx, animator->root_q );
   bitpack_qf32( ctx, 8, 0.0f, 1.0f, &animator->fly );
   bitpack_qf32( ctx, 8, 0.0f, k_runspeed, &animator->run );
   bitpack_qf32( ctx, 16, 0.0f, 120.0f, &animator->walk_timer );

   for( int i=0; i<1; i++ ){ /* without this you get a warning from gcc. lol */
      bitpack_bytes( ctx, 8, &animator->activity );
   }

   bitpack_qf32( ctx, 8, 0.0f, 1.0f, &animator->transition_t );

   if( (animator->activity == k_walk_activity_sit) || 
       (animator->activity == k_walk_activity_sit_up) ){
      bitpack_qf32( ctx, 8, -k_sit_yaw_limit, k_sit_yaw_limit, &animator->yaw );
      bitpack_qf32( ctx, 8, -k_sit_pitch_limit, k_sit_pitch_limit, 
                     &animator->pitch );
   }

   bitpack_qf32( ctx, 16, -100.0f, 100.0f, &animator->board_yaw );
}

static void player__walk_sfx_oneshot( u8 id, v3f pos, f32 volume ){
   audio_lock();

   if( id == k_player_walk_soundeffect_splash ){
      audio_oneshot_3d( &audio_splash, pos, 40.0f, 1.0f );
   }

   audio_unlock();
}
#endif /* PLAYER_DEVICE_WALK_H */