/*
PHYSICS.C

	Copyright (C) 1991-2001 and beyond by Bungie Studios, Inc.
	and the "Aleph One" developers.
 
	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	This license is contained in the file "COPYING",
	which is included with this source code; it is available online at
	http://www.gnu.org/licenses/gpl.html

Wednesday, May 11, 1994 9:32:16 AM

Saturday, May 21, 1994 11:36:31 PM
	missing effects due to map (i.e., gravity and collision detection).  last day in san
	jose after WWDC.
Sunday, May 22, 1994 11:14:55 AM
	there are two viable methods of running a synchronized network game.  the first is doom's,
	where each player shares with each other player only his control information for that tick
	(this imposes a maximum frame rate, as the state-of-the-world will be advanced at the same
	time on all machines).  the second is the continuous lag-tolerant model where each player
	shares absolute information with each other player as often as possible and local machines
	do their best at guessing what everyone else in the game is doing until they get better
	information.  whichever choice is made will change the physics drastically.  we're going to
	take the latter approach, and cache the KeyMap at interrupt time to be batch-processed
	later at frame time.

Feb. 4, 2000 (Loren Petrich):
	Changed halt() to assert(false) for better debugging

Feb 6, 2000 (Loren Petrich):
	Added access to size of physics-definition structure

Feb 20, 2000 (Loren Petrich):
	Fixed chase-cam behavior: DROP_DEAD_HEIGHT is effectively zero for it.
	Also, set up-and-down bob to zero when it is active.

Aug 31, 2000 (Loren Petrich):
	Added stuff for unpacking and packing

May 16, 2002 (Woody Zenfell):
    Letting user decide whether to auto-recenter when running

 June 14, 2003 (Woody Zenfell):
	update_player_physics_variables() can now operate in a reduced-impact mode
		that changes less of the game state.  Useful for partial-game-state
		save-and-restore code (as used by prediction mechanism).
*/

/*
running backwards shouldnÕt mean doom in a fistfight

//who decides on the physics model, anyway?  static_world-> or player->
//falling through gridlines and crapping on elevators has to do with variables->flags being wrong after the player dies
//absolute (or nearly-absolute) positioning information for yaw, pitch and velocity
//the physics model is too soft (more noticable at high frame rates)
//we can continually boot ourselves out of nearly-orthogonal walls by tiny amounts, resulting in a slide
//itÕs fairly obvious that players can still end up in walls
//the recenter key should work faster
*/

#ifdef DEBUG
//#define DIVERGENCE_CHECK
#endif

#include "cseries.h"
#include "render.h"
#include "map.h"
#include "player.h"
#include "interface.h"
#include "monsters.h"

#include "media.h"

// LP addition:
#include "ChaseCam.h"
#include "Packing.h"

#include <string.h>

#ifdef env68k
#pragma segment player
#endif

/* ---------- constants */

#define COEFFICIENT_OF_ABSORBTION 2
#define SMALL_ENOUGH_VELOCITY (constants->climbing_acceleration)
#define CLOSE_ENOUGH_TO_FLOOR WORLD_TO_FIXED(WORLD_ONE/16)

#define AIRBORNE_HEIGHT WORLD_TO_FIXED(WORLD_ONE/16)

// LP change: drop-dead height is effectively zero when the chase-cam is on;
// this keeps it from dropping.
#define DROP_DEAD_HEIGHT WORLD_TO_FIXED(ChaseCam_IsActive() ? 0 : WORLD_ONE_HALF)

#define FLAGS_WHICH_PREVENT_RECENTERING (_turning|_looking|_sidestepping|_looking_vertically|_look_dont_turn|_sidestep_dont_turn)

/* ---------- private prototypes */

/* needed for set_player_position -SB */
/*static*/ struct physics_constants *get_physics_constants_for_model(short physics_model, uint32 action_flags);
/*static*/ void instantiate_physics_variables(struct physics_constants *constants, struct physics_variables *variables, short player_index, bool first_time, bool take_action);
static void physics_update(struct physics_constants *constants, struct physics_variables *variables, struct player_data *player, uint32 action_flags);

/* ---------- globals */

/* import constants, structures and globals for physics models */
#include "physics_models.h"

/* ---------- code */

#ifdef DIVERGENCE_CHECK
#define SAVED_POINT_COUNT 8192
static world_point3d *saved_points;
static angle *saved_thetas;
static short saved_point_count, saved_point_iterations= 0;
static bool saved_divergence_warning;
#endif

/* every other field in the player structure should be valid when this call is made */
void initialize_player_physics_variables(
	short player_index)
{
	struct player_data *player= get_player_data(player_index);
	struct monster_data *monster= get_monster_data(player->monster_index);
	struct object_data *object= get_object_data(monster->object_index);
	struct physics_variables *variables= &player->variables;
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, 0);

//#ifdef DEBUG
	obj_set(*variables, 0x80);
//#endif
	
	variables->head_direction= 0;
	variables->adjusted_yaw= variables->direction= INTEGER_TO_FIXED(object->facing);
	variables->adjusted_pitch= variables->elevation= 0;
	variables->angular_velocity= variables->vertical_angular_velocity= 0;
	variables->velocity= 0, variables->perpendicular_velocity= 0;
	variables->position.x= WORLD_TO_FIXED(object->location.x);
	variables->position.y= WORLD_TO_FIXED(object->location.y);
	variables->position.z= WORLD_TO_FIXED(object->location.z);
	variables->last_position= variables->position;
	variables->last_direction= variables->direction;
	/* .floor_height, .ceiling_height and .media_height will be calculated by instantiate, below */

	variables->external_angular_velocity= 0;
	variables->external_velocity.i= variables->external_velocity.j= variables->external_velocity.k= 0;
	variables->actual_height= constants->height;
	
	variables->step_phase= 0;
	variables->step_amplitude= 0;
	
	variables->action= _player_stationary;
	variables->old_flags= variables->flags= 0; /* not recentering, not above ground, not below ground (i.e., on floor) */

	/* setup shadow variables in player_data structure */
	instantiate_physics_variables(get_physics_constants_for_model(static_world->physics_model, 0),
		&player->variables, player_index, true, true);

#ifdef DIVERGENCE_CHECK
	if (!saved_point_iterations)
	{
		saved_points= new world_point3d[SAVED_POINT_COUNT];
		saved_thetas= new angle[SAVED_POINT_COUNT];
	}
	saved_point_count= 0;
	saved_point_iterations+= 1;
	saved_divergence_warning= false;
#endif
}

void update_player_physics_variables(
	short player_index,
	uint32 action_flags,
	bool predictive)
{
	struct player_data *player= get_player_data(player_index);
	struct physics_variables *variables= &player->variables;
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, action_flags);

	physics_update(constants, variables, player, action_flags);
	instantiate_physics_variables(constants, variables, player_index, false, !predictive);

#ifdef DIVERGENCE_CHECK
	if (saved_point_count<SAVED_POINT_COUNT)
	{
		struct object_data *object= get_object_data(get_monster_data(player->monster_index)->object_index);
		world_point3d p= object->location;
		world_point3d *q= saved_points+saved_point_count;
		angle *facing= saved_thetas+saved_point_count;
		
		if (saved_point_iterations==1)
		{
			saved_points[saved_point_count]= p;
			*facing= object->facing;
		}
		else
		{
			if (p.x!=q->x||p.y!=q->y||p.z!=q->z||*facing!=object->facing&&!saved_divergence_warning)
			{
				dprintf("divergence @ tick %d: (%d,%d,%d,%d)!=(%d,%d,%d,%d)", saved_point_count,
					q->x, q->y, q->z, *facing, p.x, p.y, p.z, object->facing);
				saved_divergence_warning= true;
			}
		}
		
		saved_point_count+= 1;
	}
#endif
}

void adjust_player_for_polygon_height_change(
	short monster_index,
	short polygon_index,
	world_distance new_floor_height,
	world_distance new_ceiling_height)
{
	short player_index= monster_index_to_player_index(monster_index);
	struct player_data *player= get_player_data(player_index);
	struct physics_variables *variables= &player->variables;
	struct polygon_data *polygon= get_polygon_data(polygon_index);
	world_distance old_floor_height= polygon->floor_height;

	(void) (new_ceiling_height);

	if (player->supporting_polygon_index==polygon_index)
	{
		if (FIXED_TO_WORLD(variables->position.z)<=old_floor_height) /* must be <= */
		{
			variables->floor_height= variables->position.z= WORLD_TO_FIXED(new_floor_height);
			if (PLAYER_IS_DEAD(player)) variables->external_velocity.k= 0;
		}
	}
}

void accelerate_player(
	short monster_index,
	world_distance vertical_velocity,
	angle direction,
	world_distance velocity)
{
	short player_index= monster_index_to_player_index(monster_index);
	struct player_data *player= get_player_data(player_index);
	struct physics_variables *variables= &player->variables;
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, 0);

	variables->external_velocity.k+= WORLD_TO_FIXED(vertical_velocity);
	variables->external_velocity.k= PIN(variables->external_velocity.k, -constants->terminal_velocity, constants->terminal_velocity);
	
	variables->external_velocity.i+= (cosine_table[direction]*velocity)>>(TRIG_SHIFT+WORLD_FRACTIONAL_BITS-FIXED_FRACTIONAL_BITS);
	variables->external_velocity.j+= (sine_table[direction]*velocity)>>(TRIG_SHIFT+WORLD_FRACTIONAL_BITS-FIXED_FRACTIONAL_BITS);
}

void get_absolute_pitch_range(
	_fixed *minimum,
	_fixed *maximum)
{
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, 0);
	
	*minimum= -constants->maximum_elevation;
	*maximum= constants->maximum_elevation;
}

/* deltas of zero are ignored; all deltas must be in [-FIXED_ONE,FIXED_ONE] which will be scaled
	to the maximum for that value */
uint32 mask_in_absolute_positioning_information(
	uint32 action_flags,
	_fixed delta_yaw,
	_fixed delta_pitch,
	_fixed delta_position)
{
	struct physics_variables *variables= &local_player->variables;
	short encoded_delta;

	if ((delta_yaw||variables->angular_velocity) && !(action_flags&_override_absolute_yaw))
	{
//		if (delta_yaw<0 && delta_yaw>((-1)<<(FIXED_FRACTIONAL_BITS-ABSOLUTE_YAW_BITS))) delta_yaw= 0;
		if (delta_yaw>0 && delta_yaw<((1)<<(FIXED_FRACTIONAL_BITS-ABSOLUTE_YAW_BITS))) delta_yaw= (1)<<(FIXED_FRACTIONAL_BITS-ABSOLUTE_YAW_BITS);
		encoded_delta= (delta_yaw>>(FIXED_FRACTIONAL_BITS-ABSOLUTE_YAW_BITS))+MAXIMUM_ABSOLUTE_YAW/2;
		encoded_delta= PIN(encoded_delta, 0, MAXIMUM_ABSOLUTE_YAW-1);
		action_flags= SET_ABSOLUTE_YAW(action_flags, encoded_delta)|_absolute_yaw_mode;
	}

	if ((delta_pitch||variables->vertical_angular_velocity) && !(action_flags&_override_absolute_pitch))
	{
//		if (delta_pitch<0 && delta_pitch>((-1)<<(FIXED_FRACTIONAL_BITS-ABSOLUTE_PITCH_BITS))) delta_pitch= 0;
		if (delta_pitch>0 && delta_pitch<((1)<<(FIXED_FRACTIONAL_BITS-ABSOLUTE_PITCH_BITS))) delta_pitch= (1)<<(FIXED_FRACTIONAL_BITS-ABSOLUTE_PITCH_BITS);
		encoded_delta= (delta_pitch>>(FIXED_FRACTIONAL_BITS-ABSOLUTE_PITCH_BITS))+MAXIMUM_ABSOLUTE_PITCH/2;
		encoded_delta= PIN(encoded_delta, 0, MAXIMUM_ABSOLUTE_PITCH-1);
		action_flags= SET_ABSOLUTE_PITCH(action_flags, encoded_delta)|_absolute_pitch_mode;
	}

	if (delta_position && !(action_flags&_override_absolute_position))
	{
		encoded_delta= (delta_position>>(FIXED_FRACTIONAL_BITS-ABSOLUTE_POSITION_BITS))+MAXIMUM_ABSOLUTE_POSITION/2;
		encoded_delta= PIN(encoded_delta, 0, MAXIMUM_ABSOLUTE_POSITION-1);
		action_flags= SET_ABSOLUTE_POSITION(action_flags, encoded_delta)|_absolute_position_mode;
	}

	return action_flags;
}

/* will be obsolete when cybermaxx changes to new-style */
void instantiate_absolute_positioning_information(
	short player_index,
	_fixed facing,
	_fixed elevation)
{
	struct player_data *player= get_player_data(player_index);
	struct physics_variables *variables= &player->variables;
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, 0);

	assert(elevation>=-INTEGER_TO_FIXED(QUARTER_CIRCLE)&&elevation<=INTEGER_TO_FIXED(QUARTER_CIRCLE));
	assert(facing>=0&&facing<INTEGER_TO_FIXED(FULL_CIRCLE));

	variables->elevation= PIN(elevation, -constants->maximum_elevation, constants->maximum_elevation);
	variables->vertical_angular_velocity= 0;

	variables->direction= facing;

	instantiate_physics_variables(constants, variables, player_index, false, true);
}

void get_binocular_vision_origins(
	short player_index,
	world_point3d *left,
	short *left_polygon_index,
	angle *left_angle,
	world_point3d *right,
	short *right_polygon_index,
	angle *right_angle)
{
	struct player_data *player= get_player_data(player_index);
	struct physics_variables *variables= &player->variables;
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, 0);
	angle theta;

	theta= NORMALIZE_ANGLE(player->facing+QUARTER_CIRCLE);
	right->x= FIXED_TO_WORLD(variables->position.x + ((constants->half_camera_separation*cosine_table[theta])>>TRIG_SHIFT));
	right->y= FIXED_TO_WORLD(variables->position.y + ((constants->half_camera_separation*sine_table[theta])>>TRIG_SHIFT));
	right->z= player->camera_location.z;
	*right_polygon_index= find_new_object_polygon((world_point2d *)&player->camera_location, (world_point2d *)right, player->camera_polygon_index);
	*right_angle= NORMALIZE_ANGLE(player->facing-1);
	
	theta= NORMALIZE_ANGLE(player->facing-QUARTER_CIRCLE);
	left->x= FIXED_TO_WORLD(variables->position.x + ((constants->half_camera_separation*cosine_table[theta])>>TRIG_SHIFT));
	left->y= FIXED_TO_WORLD(variables->position.y + ((constants->half_camera_separation*sine_table[theta])>>TRIG_SHIFT));
	left->z= player->camera_location.z;
	*left_polygon_index= find_new_object_polygon((world_point2d *)&player->camera_location, (world_point2d *)left, player->camera_polygon_index);
	*left_angle= NORMALIZE_ANGLE(player->facing+1);
}

void kill_player_physics_variables(
	short player_index)
{
}

/* return a number in [-FIXED_ONE,FIXED_ONE] (arguably) */
_fixed get_player_forward_velocity_scale(
	short player_index)
{
	struct player_data *player= get_player_data(player_index);
	struct physics_variables *variables= &player->variables;
	struct physics_constants *constants= get_physics_constants_for_model(static_world->physics_model, _run_dont_walk);
	_fixed dx= variables->position.x - variables->last_position.x;
	_fixed dy= variables->position.y - variables->last_position.y;

	return INTEGER_TO_FIXED(((dx*cosine_table[FIXED_INTEGERAL_PART(variables->direction)] +
		dy*sine_table[FIXED_INTEGERAL_PART(variables->direction)])>>TRIG_SHIFT))/constants->maximum_forward_velocity;
}



/* ---------- private code */

/*static*/ struct physics_constants *get_physics_constants_for_model(
	short physics_model,
	uint32 action_flags)
{
	struct physics_constants *constants;
	
	switch (physics_model)
	{
		case _editor_model:
		case _earth_gravity_model: constants= physics_models + ((action_flags&_run_dont_walk) ? _model_game_running : _model_game_walking); break;
		case _low_gravity_model:
			assert(false);
			break;
		default:
			assert(false);
			break;
	}
	
	return constants;
}

/*static*/ void instantiate_physics_variables(
	struct physics_constants *constants,
	struct physics_variables *variables,
	short player_index,
	bool first_time,
	bool take_action)
{
	struct player_data *player= get_player_data(player_index);
	struct monster_data *monster= get_monster_data(player->monster_index);
	struct object_data *legs= get_object_data(monster->object_index);
	struct object_data *torso= get_object_data(legs->parasitic_object);
	short old_polygon_index= legs->polygon;
	world_point3d new_location;
	world_distance adjusted_floor_height, adjusted_ceiling_height, object_floor;
	bool clipped;
	_fixed step_height;
	angle facing, elevation;
	_fixed fixed_facing;

	/* convert to world coordinates before doing collision detection */
	new_location.x= FIXED_TO_WORLD(variables->position.x);
	new_location.y= FIXED_TO_WORLD(variables->position.y);
	new_location.z= FIXED_TO_WORLD(variables->position.z);

	/* check for 2d collisions with walls and knock the player back out of the wall (because of
		the way the physics updates work, we donÕt worry about collisions with the floor or
		ceiling).  ONLY MODIFY THE PLAYERÕS FIXED_POINT3D POSITION IF WE HAD A COLLISION */
	if (PLAYER_IS_DEAD(player)) new_location.z+= FIXED_TO_WORLD(DROP_DEAD_HEIGHT);
	if (take_action && !first_time && player->last_supporting_polygon_index!=player->supporting_polygon_index) changed_polygon(player->last_supporting_polygon_index, player->supporting_polygon_index, player_index);
	player->last_supporting_polygon_index= first_time ? NONE : player->supporting_polygon_index;
	clipped= keep_line_segment_out_of_walls(legs->polygon, &legs->location, &new_location,
		WORLD_ONE/3, FIXED_TO_WORLD(variables->actual_height), &adjusted_floor_height, &adjusted_ceiling_height,
		&player->supporting_polygon_index);
	if (PLAYER_IS_DEAD(player)) new_location.z-= FIXED_TO_WORLD(DROP_DEAD_HEIGHT);

	/* check for 2d collisions with solid objects and knock the player back out of the object.
		ONLY MODIFY THE PLAYERÕS FIXED_POINT3D POSITION IF WE HAD A COLLISION. */
	object_floor= INT16_MIN;
	{
		short obstruction_index= legal_player_move(player->monster_index, &new_location, &object_floor);
		
		if (obstruction_index!=NONE)
		{
			struct object_data *object= get_object_data(obstruction_index);
			
			switch (GET_OBJECT_OWNER(object))
			{
				case _object_is_monster:
					if(take_action)
						bump_monster(player->monster_index, object->permutation);
				case _object_is_scenery:
					new_location.x= legs->location.x, new_location.y= legs->location.y;
					clipped= true;
					break;
				
				default:
					assert(false);
					break;
			}
		}
	}

	/* translate_map_object will handle crossing polygon boundaries */
	if (translate_map_object(monster->object_index, &new_location, NONE))
	{
		if (old_polygon_index==legs->polygon) clipped= true; /* oops; trans_map_obj destructively changed our position */
		if(take_action)
			monster_moved(player->monster_index, old_polygon_index);
	}

	/* if our move got clipped, copy the new coordinate back into the physics variables */
	if (clipped)
	{
		variables->position.x= WORLD_TO_FIXED(new_location.x);
		variables->position.y= WORLD_TO_FIXED(new_location.y);
		variables->position.z= WORLD_TO_FIXED(new_location.z);
	}
	
	/* shadow position in player structure, build camera location */
	// LP change: no camera bob when the ChaseCam is active
	if (ChaseCam_IsActive())
		step_height = 0;
	else
	{
		step_height= (constants->step_amplitude*sine_table[variables->step_phase>>(FIXED_FRACTIONAL_BITS-ANGULAR_BITS+1)])>>TRIG_SHIFT;
		step_height= (step_height*variables->step_amplitude)>>FIXED_FRACTIONAL_BITS;
	}
	player->camera_location= new_location;
	if (PLAYER_IS_DEAD(player) && new_location.z<adjusted_floor_height) new_location.z= adjusted_floor_height;
	player->location= new_location;
	player->camera_location.z+= FIXED_TO_WORLD(step_height+variables->actual_height-constants->camera_height);
	player->camera_polygon_index= legs->polygon;

	/* shadow facing in player structure and object structure */
	fixed_facing= variables->direction+variables->head_direction;
	facing= FIXED_INTEGERAL_PART(fixed_facing), facing= NORMALIZE_ANGLE(facing);
	elevation= FIXED_INTEGERAL_PART(variables->elevation), elevation= NORMALIZE_ANGLE(elevation);
	legs->location.z= player->location.z;
	legs->facing= NORMALIZE_ANGLE(FIXED_INTEGERAL_PART(variables->direction)), torso->facing= player->facing= facing;
	player->elevation= elevation;

	/* initialize floor_height and ceiling_height for next call to physics_update() */
	variables->floor_height= WORLD_TO_FIXED(MAX(adjusted_floor_height, object_floor));
	variables->ceiling_height= WORLD_TO_FIXED(adjusted_ceiling_height);
	{
		short media_index= get_polygon_data(legs->polygon)->media_index;
		// LP change: idiot-proofing
		media_data *media = get_media_data(media_index);
		world_distance media_height= (media_index==NONE || !media) ? INT16_MIN : media->height;

		if (player->location.z<media_height) variables->flags|= _FEET_BELOW_MEDIA_BIT; else variables->flags&= (uint16)~_FEET_BELOW_MEDIA_BIT;
		if (player->camera_location.z<media_height) variables->flags|= _HEAD_BELOW_MEDIA_BIT; else variables->flags&= (uint16)~_HEAD_BELOW_MEDIA_BIT;
	}

	// so our sounds come from the right place
	monster->sound_location= player->camera_location;
	monster->sound_polygon_index= player->camera_polygon_index;
}

/* separate physics_constant structures are passed in for running/walking modes */
// ZZZ note: 'player' is only used in this routine for PLAYER_IS_DEAD(player) - as such,
// perhaps this should take an "is_dead" flag as a parameter instead of the player structure.
static void physics_update(
	struct physics_constants *constants,
	struct physics_variables *variables,
	struct player_data *player,
	uint32 action_flags)
{
	fixed_point3d new_position;
	short sine, cosine;
	_fixed delta_z;
	_fixed delta; /* used as a scratch ÔchangeÕ variable */

	if (PLAYER_IS_DEAD(player)) /* dead players immediately loose all bodily control */
	{
		long dot_product;
		
		cosine= cosine_table[FIXED_INTEGERAL_PART(variables->direction)], sine= sine_table[FIXED_INTEGERAL_PART(variables->direction)];
		dot_product= ((((variables->velocity*cosine)>>TRIG_SHIFT) + variables->external_velocity.i)*cosine +
			(((variables->velocity*sine)>>TRIG_SHIFT) + variables->external_velocity.j)*sine)>>TRIG_SHIFT;

		if (dot_product>0 && dot_product<(constants->maximum_forward_velocity>>4)) dot_product= 0;
		switch (SGN(dot_product))
		{
			case -1: action_flags= _looking_up; break;
			case 1: action_flags= _looking_down; break;
			case 0: action_flags= 0; break;
			default:
				assert(false);
				break;
		}
		
		variables->floor_height-= DROP_DEAD_HEIGHT;
	}
	delta_z= variables->position.z-variables->floor_height;

	/* process modifier keys (sidestepping and looking) into normal actions */
	if ((action_flags&_turning) && (action_flags&_sidestep_dont_turn) && !(action_flags&_absolute_yaw_mode))
	{
		if (action_flags&_turning_left) action_flags|= _sidestepping_left;
		if (action_flags&_turning_right) action_flags|= _sidestepping_right;
		action_flags&= ~_turning;
	}
	if ((action_flags&_moving) && (action_flags&_look_dont_turn) && !(action_flags&_absolute_position_mode))
	{
		if (action_flags&_moving_forward) action_flags|= _looking_up;
		if (action_flags&_moving_backward) action_flags|= _looking_down;
		action_flags&= ~_moving;
		action_flags&= ~_absolute_pitch_mode;
	}

	/* handle turning left or right; if weÕve exceeded our maximum velocity lock out user actions
		until we return to a legal range */
	if (action_flags&_absolute_yaw_mode)
	{
		variables->angular_velocity= (GET_ABSOLUTE_YAW(action_flags)-MAXIMUM_ABSOLUTE_YAW/2)<<(FIXED_FRACTIONAL_BITS); // !!!!!!!!!!
	}
	else
	{
		if (variables->angular_velocity<-constants->maximum_angular_velocity||variables->angular_velocity>constants->maximum_angular_velocity) action_flags&= ~_turning;
		switch (action_flags&_turning)
		{
			case _turning_left:
				delta= variables->angular_velocity>0 ? constants->angular_acceleration+constants->angular_deceleration : constants->angular_acceleration;
				variables->angular_velocity= FLOOR(variables->angular_velocity-delta, -constants->maximum_angular_velocity);
				break;
			case _turning_right:
				delta= variables->angular_velocity<0 ? constants->angular_acceleration+constants->angular_deceleration : constants->angular_acceleration;
				variables->angular_velocity= CEILING(variables->angular_velocity+delta, constants->maximum_angular_velocity);
				break;
			
			default: /* slow down */
				variables->angular_velocity= (variables->angular_velocity>=0) ?
					FLOOR(variables->angular_velocity-constants->angular_deceleration, 0) :
					CEILING(variables->angular_velocity+constants->angular_deceleration, 0);
				break;
		}
		
		/* handling looking left/right */
		switch (action_flags&_looking)
		{
			case _looking_left:
				variables->head_direction= FLOOR(variables->head_direction-constants->fast_angular_velocity, -constants->fast_angular_maximum);
				break;
			case _looking_right:
				variables->head_direction= CEILING(variables->head_direction+constants->fast_angular_velocity, constants->fast_angular_maximum);
				break;
			case _looking: /* do nothing if both keys are down */
				break;
			
			default: /* recenter head */
				variables->head_direction= (variables->head_direction>=0) ?
					FLOOR(variables->head_direction-constants->fast_angular_velocity, 0) :
					CEILING(variables->head_direction+constants->fast_angular_velocity, 0);
		}
	}

	if (action_flags&_absolute_pitch_mode)
	{
		variables->vertical_angular_velocity= (GET_ABSOLUTE_PITCH(action_flags)-MAXIMUM_ABSOLUTE_PITCH/2)<<(FIXED_FRACTIONAL_BITS);
	}
	else
	{
		/* if the user touched the recenter key, set the recenter flag and override all up/down
			keypresses with our own */
		if (action_flags&_looking_center) variables->flags|= _RECENTERING_BIT;
		if (variables->flags&_RECENTERING_BIT)
		{
			action_flags&= ~_looking_vertically;
			action_flags|= variables->elevation<0 ? _looking_up : _looking_down;
		}
	
		/* handle looking up and down; if weÕre moving at our terminal velocity forward or backward,
			without any side-to-side motion, recenter our head vertically */

        // ZZZ: only do auto-recentering if the user wants it
        if(!PLAYER_DOESNT_AUTO_RECENTER(player)) {
            if (!(action_flags&FLAGS_WHICH_PREVENT_RECENTERING)) /* canÕt recenter if any of these are true */
		    {
			    if (((action_flags&_moving_forward) && (variables->velocity==constants->maximum_forward_velocity)) ||
				    ((action_flags&_moving_backward) && (variables->velocity==-constants->maximum_backward_velocity)))
			    {
				    if (variables->elevation<0)
				    {
					    variables->elevation= CEILING(variables->elevation+constants->angular_recentering_velocity, 0);
				    }
				    else
				    {
					    variables->elevation= FLOOR(variables->elevation-constants->angular_recentering_velocity, 0);
				    }
			    }
		    }
        }

		switch (action_flags&_looking_vertically)
		{
			case _looking_down:
				delta= variables->vertical_angular_velocity>0 ? constants->angular_acceleration+constants->angular_deceleration : constants->angular_acceleration;
				variables->vertical_angular_velocity= FLOOR(variables->vertical_angular_velocity-delta, PLAYER_IS_DEAD(player) ? -(constants->maximum_angular_velocity>>3) : -constants->maximum_angular_velocity);
				break;
			case _looking_up:
				delta= variables->vertical_angular_velocity<0 ? constants->angular_acceleration+constants->angular_deceleration : constants->angular_acceleration;
				variables->vertical_angular_velocity= CEILING(variables->vertical_angular_velocity+delta, PLAYER_IS_DEAD(player) ? (constants->maximum_angular_velocity>>3) : constants->maximum_angular_velocity);
				break;
			
			default: /* if no key is being held down, decelerate; if the player is moving try and return to phi==0 */
				variables->vertical_angular_velocity= (variables->vertical_angular_velocity>=0) ?
					FLOOR(variables->vertical_angular_velocity-constants->angular_deceleration, 0) :
					CEILING(variables->vertical_angular_velocity+constants->angular_deceleration, 0);
				break;
		}
	}

	/* if weÕre on the ground (or rising up from it), allow movement; if weÕre flying through
		the air, donÕt let the player adjust his velocity in any way */
	if (delta_z<=0 || (variables->flags&_HEAD_BELOW_MEDIA_BIT))
	{
		if (action_flags&_absolute_position_mode)
		{
			short encoded_delta= GET_ABSOLUTE_POSITION(action_flags)-MAXIMUM_ABSOLUTE_POSITION/2;
			
			if (encoded_delta<0)
			{
				variables->velocity= (encoded_delta*constants->maximum_backward_velocity)>>(ABSOLUTE_POSITION_BITS-1);
			}
			else
			{
				variables->velocity= (encoded_delta*constants->maximum_forward_velocity)>>(ABSOLUTE_POSITION_BITS-1);
			}
		}
		else
		{
			/* handle moving forward or backward; if weÕve exceeded our maximum velocity lock out user actions
				until we return to a legal range */
			if (variables->velocity<-constants->maximum_backward_velocity||variables->velocity>constants->maximum_forward_velocity) action_flags&= ~_moving;
			switch (action_flags&_moving)
			{
				case _moving_forward:
					delta= variables->velocity<0 ? constants->deceleration+constants->acceleration : constants->acceleration;
					variables->velocity= CEILING(variables->velocity+delta, constants->maximum_forward_velocity);
					break;
				case _moving_backward:
					delta= variables->velocity>0 ? constants->deceleration+constants->acceleration : constants->acceleration;
					variables->velocity= FLOOR(variables->velocity-delta, -constants->maximum_backward_velocity);
					break;
				
				default: /* slow down */
					variables->velocity= (variables->velocity>=0) ?
						FLOOR(variables->velocity-constants->deceleration, 0) :
						CEILING(variables->velocity+constants->deceleration, 0);
					break;
			}
		}
		
		/* handle sidestepping left or right; if weÕve exceeded our maximum velocity lock out user actions
			until we return to a legal range */
		if (variables->perpendicular_velocity<-constants->maximum_perpendicular_velocity||variables->perpendicular_velocity>constants->maximum_perpendicular_velocity) action_flags&= ~_sidestepping;
		switch (action_flags&_sidestepping)
		{
			case _sidestepping_left:
				delta= variables->perpendicular_velocity>0 ? constants->acceleration+constants->deceleration : constants->acceleration;
				variables->perpendicular_velocity= FLOOR(variables->perpendicular_velocity-delta, -constants->maximum_perpendicular_velocity);
				break;
			case _sidestepping_right:
				delta= variables->perpendicular_velocity<0 ? constants->acceleration+constants->deceleration : constants->acceleration;
				variables->perpendicular_velocity= CEILING(variables->perpendicular_velocity+delta, constants->maximum_perpendicular_velocity);
				break;
			
			default: /* slow down */
				variables->perpendicular_velocity= (variables->perpendicular_velocity>=0) ?
					FLOOR(variables->perpendicular_velocity-constants->deceleration, 0) :
					CEILING(variables->perpendicular_velocity+constants->deceleration, 0);
				break;
		}
	}
	
	/* change vertical_velocity based on difference between player height and surface height
		(if we are standing on an object, like a body, take that into account, too: this
		means a player could actually use bodies as ramps to reach ledges he couldn't
		otherwise jump to).  we should think about absorbing forward (or perpendicular)
		velocity to compensate for an increase in vertical velocity, which would slow down
		a player climbing stairs, etc. */
	if (delta_z<0)
	{
		variables->external_velocity.k= CEILING(variables->external_velocity.k+constants->climbing_acceleration, constants->terminal_velocity);
	}
	if (delta_z>0)
	{
		_fixed gravity= constants->gravitational_acceleration;
		_fixed terminal_velocity= constants->terminal_velocity;
		
		if (static_world->environment_flags&_environment_low_gravity) gravity>>= 1;
		if (variables->flags&_FEET_BELOW_MEDIA_BIT) gravity>>= 1, terminal_velocity>>= 1;
		
		variables->external_velocity.k= FLOOR(variables->external_velocity.k-gravity, -terminal_velocity);
	}

	if ((action_flags&_swim) && (variables->flags&_HEAD_BELOW_MEDIA_BIT) && variables->external_velocity.k<10*constants->climbing_acceleration)
	{
		variables->external_velocity.k+= constants->climbing_acceleration;
	}

	/* change the playerÕs elevation based on his vertical angular velocity; if weÕre recentering and
		have recentered clear the recentering bit */
	variables->elevation+= variables->vertical_angular_velocity;
	variables->elevation= PIN(variables->elevation, -constants->maximum_elevation, constants->maximum_elevation);
	if ((variables->flags&_RECENTERING_BIT) && !(action_flags&_absolute_pitch_mode))
	{
		if ((variables->elevation<=0&&(action_flags&_looking_down))||(variables->elevation>=0&&(action_flags&_looking_up)))
		{
			variables->elevation= variables->vertical_angular_velocity= 0;
			variables->flags&= (uint16)~_RECENTERING_BIT;
		}
	}

	/* change the playerÕs heading based on his angular velocities */
	variables->last_direction= variables->direction;
	variables->direction+= variables->angular_velocity;
	if (variables->direction<0) variables->direction+= INTEGER_TO_FIXED(FULL_CIRCLE);
	if (variables->direction>=INTEGER_TO_FIXED(FULL_CIRCLE)) variables->direction-= INTEGER_TO_FIXED(FULL_CIRCLE);
	
	/* change the playerÕs x,y position based on his direction and velocities (parallel and perpendicular)  */
	new_position= variables->position;
	cosine= cosine_table[FIXED_INTEGERAL_PART(variables->direction)], sine= sine_table[FIXED_INTEGERAL_PART(variables->direction)];
	new_position.x+= (variables->velocity*cosine-variables->perpendicular_velocity*sine)>>TRIG_SHIFT;
	new_position.y+= (variables->velocity*sine+variables->perpendicular_velocity*cosine)>>TRIG_SHIFT;
	
	/* set above/below floor flags, remember old flags */
	variables->old_flags= variables->flags;
	if (new_position.z<variables->floor_height) variables->flags|= _BELOW_GROUND_BIT; else variables->flags&= (uint16)~_BELOW_GROUND_BIT;
	if (new_position.z>variables->floor_height) variables->flags|= _ABOVE_GROUND_BIT; else variables->flags&= (uint16)~_ABOVE_GROUND_BIT;

	/* if we just landed on the ground, or we just came up through the ground, absorb some of
		the playerÕs external_velocity.k (and in the case of hitting the ground, reflect it) */
	if (variables->external_velocity.k>0 && (variables->old_flags&_BELOW_GROUND_BIT) && !(variables->flags&_BELOW_GROUND_BIT))
	{
		variables->external_velocity.k/= 2*COEFFICIENT_OF_ABSORBTION; /* slow down */
	}
	if (variables->external_velocity.k>0 && new_position.z+variables->actual_height>=variables->ceiling_height)
	{
		variables->external_velocity.k/= -COEFFICIENT_OF_ABSORBTION, new_position.z= variables->ceiling_height-variables->actual_height; // &&variables->position.z+variables->actual_height<variables->ceiling_height
	}
	if (variables->external_velocity.k<0&&!(variables->old_flags&_BELOW_GROUND_BIT)&&!(variables->flags&_ABOVE_GROUND_BIT))
	{
		variables->external_velocity.k/= -COEFFICIENT_OF_ABSORBTION;
	}
	if (ABS(variables->external_velocity.k)<SMALL_ENOUGH_VELOCITY &&
		ABS(variables->floor_height-new_position.z)<CLOSE_ENOUGH_TO_FLOOR)
	{
		variables->external_velocity.k= 0, new_position.z= variables->floor_height;
		variables->flags&= ~(_BELOW_GROUND_BIT|_ABOVE_GROUND_BIT);
	}

	/* change the playerÕs z position based on his vertical velocity (if we hit the ground coming down
		then bounce and absorb most of the blow */
	new_position.x+= variables->external_velocity.i;
	new_position.y+= variables->external_velocity.j;
	new_position.z+= variables->external_velocity.k;
	
	{
		short dx= variables->external_velocity.i, dy= variables->external_velocity.j;
		_fixed delta= (delta_z<=0) ? constants->external_deceleration : (constants->external_deceleration>>2);
		long magnitude= isqrt(dx*dx + dy*dy);

		if (magnitude && magnitude>ABS(delta))
		{
			variables->external_velocity.i-= (dx*delta)/magnitude;
			variables->external_velocity.j-= (dy*delta)/magnitude;
		}
		else
		{
			variables->external_velocity.i= variables->external_velocity.j= 0;
		}
	}

	/* lower the playerÕs externally-induced angular velocity */
	variables->external_angular_velocity= (variables->external_angular_velocity>=0) ?
		FLOOR(variables->external_angular_velocity-constants->external_angular_deceleration, 0) :
		CEILING(variables->external_angular_velocity+constants->external_angular_deceleration, 0);

	/* instantiate new position, save old position */
	variables->last_position= variables->position;
	variables->position= new_position;

	/* if the player is moving, adjust step_phase by step_delta (if the player isnÕt moving
		continue to adjust step_phase until it is zero)  if the player is in the air, donÕt
		update phase until he lands. */
	variables->flags&= (uint16)~_STEP_PERIOD_BIT;
	if (constants->maximum_forward_velocity)
		variables->step_amplitude= (MAX(ABS(variables->velocity), ABS(variables->perpendicular_velocity))*FIXED_ONE)/constants->maximum_forward_velocity;
	else	// CB: "Missed Island" physics would produce a division by 0
		variables->step_amplitude= MAX(ABS(variables->velocity), ABS(variables->perpendicular_velocity))*FIXED_ONE;
	if (delta_z>=0)
	{
		if (variables->velocity||variables->perpendicular_velocity)
		{
//			fixed old_step_phase= variables->step_phase;
			
			if ((variables->step_phase+= constants->step_delta)>=FIXED_ONE)
			{
				variables->step_phase-= FIXED_ONE;
				variables->flags|= _STEP_PERIOD_BIT;
			}
//			else
//			{
//				if (variables->step_phase>=FIXED_ONE_HALF && old_step_phase<FIXED_ONE_HALF)
//				{
//					variables->flags|= _STEP_PERIOD_BIT;
//				}
//			}
		}
		else
		{
			if (variables->step_phase)
			{
				if (variables->step_phase>FIXED_ONE_HALF)
				{
					if ((variables->step_phase+= constants->step_delta)>=FIXED_ONE) variables->step_phase= 0;
				}
				else
				{
					if ((variables->step_phase-= constants->step_delta)<0) variables->step_phase= 0;
				}
			}
		}
	}

	if (delta_z >= (PLAYER_IS_DEAD(player) ? (AIRBORNE_HEIGHT+DROP_DEAD_HEIGHT) : AIRBORNE_HEIGHT))
	{
		variables->action= _player_airborne;
	}
	else
	{
		if (variables->angular_velocity||variables->velocity||variables->perpendicular_velocity)
		{
			variables->action= (action_flags&_run_dont_walk) ? _player_running : _player_walking;
		}
		else
		{
			variables->action= (variables->external_velocity.i||variables->external_velocity.j||variables->external_velocity.k) ? _player_sliding : _player_stationary;
		}
	}
}


uint8 *unpack_physics_constants(uint8 *Stream, size_t Count)
{
	return unpack_physics_constants(Stream,physics_models,Count);
}

uint8 *unpack_physics_constants(uint8 *Stream, physics_constants *Objects, size_t Count)
{
	uint8* S = Stream;
	physics_constants* ObjPtr = Objects;
	
	for (size_t k = 0; k < Count; k++, ObjPtr++)
	{
		StreamToValue(S,ObjPtr->maximum_forward_velocity);
		StreamToValue(S,ObjPtr->maximum_backward_velocity);
		StreamToValue(S,ObjPtr->maximum_perpendicular_velocity);
		StreamToValue(S,ObjPtr->acceleration);
		StreamToValue(S,ObjPtr->deceleration);
		StreamToValue(S,ObjPtr->airborne_deceleration);
		StreamToValue(S,ObjPtr->gravitational_acceleration);
		StreamToValue(S,ObjPtr->climbing_acceleration);
		StreamToValue(S,ObjPtr->terminal_velocity);
		StreamToValue(S,ObjPtr->external_deceleration);

		StreamToValue(S,ObjPtr->angular_acceleration);
		StreamToValue(S,ObjPtr->angular_deceleration);
		StreamToValue(S,ObjPtr->maximum_angular_velocity);
		StreamToValue(S,ObjPtr->angular_recentering_velocity);
		StreamToValue(S,ObjPtr->fast_angular_velocity);
		StreamToValue(S,ObjPtr->fast_angular_maximum);
		StreamToValue(S,ObjPtr->maximum_elevation);
		StreamToValue(S,ObjPtr->external_angular_deceleration);
		
		StreamToValue(S,ObjPtr->step_delta);
		StreamToValue(S,ObjPtr->step_amplitude);
		StreamToValue(S,ObjPtr->radius);
		StreamToValue(S,ObjPtr->height);
		StreamToValue(S,ObjPtr->dead_height);
		StreamToValue(S,ObjPtr->camera_height);
		StreamToValue(S,ObjPtr->splash_height);
		
		StreamToValue(S,ObjPtr->half_camera_separation);
	}
	
	assert((S - Stream) == static_cast<ptrdiff_t>(Count*SIZEOF_physics_constants));
	return S;
}

uint8 *pack_physics_constants(uint8 *Stream, size_t Count)
{
	return pack_physics_constants(Stream,physics_models,Count);
}

uint8 *pack_physics_constants(uint8 *Stream, physics_constants *Objects, size_t Count)
{
	uint8* S = Stream;
	physics_constants* ObjPtr = Objects;
	
	for (size_t k = 0; k < Count; k++, ObjPtr++)
	{
		ValueToStream(S,ObjPtr->maximum_forward_velocity);
		ValueToStream(S,ObjPtr->maximum_backward_velocity);
		ValueToStream(S,ObjPtr->maximum_perpendicular_velocity);
		ValueToStream(S,ObjPtr->acceleration);
		ValueToStream(S,ObjPtr->deceleration);
		ValueToStream(S,ObjPtr->airborne_deceleration);
		ValueToStream(S,ObjPtr->gravitational_acceleration);
		ValueToStream(S,ObjPtr->climbing_acceleration);
		ValueToStream(S,ObjPtr->terminal_velocity);
		ValueToStream(S,ObjPtr->external_deceleration);

		ValueToStream(S,ObjPtr->angular_acceleration);
		ValueToStream(S,ObjPtr->angular_deceleration);
		ValueToStream(S,ObjPtr->maximum_angular_velocity);
		ValueToStream(S,ObjPtr->angular_recentering_velocity);
		ValueToStream(S,ObjPtr->fast_angular_velocity);
		ValueToStream(S,ObjPtr->fast_angular_maximum);
		ValueToStream(S,ObjPtr->maximum_elevation);
		ValueToStream(S,ObjPtr->external_angular_deceleration);
		
		ValueToStream(S,ObjPtr->step_delta);
		ValueToStream(S,ObjPtr->step_amplitude);
		ValueToStream(S,ObjPtr->radius);
		ValueToStream(S,ObjPtr->height);
		ValueToStream(S,ObjPtr->dead_height);
		ValueToStream(S,ObjPtr->camera_height);
		ValueToStream(S,ObjPtr->splash_height);
		
		ValueToStream(S,ObjPtr->half_camera_separation);
	}
	
	assert((S - Stream) == static_cast<ptrdiff_t>(Count*SIZEOF_physics_constants));
	return S;
}

void init_physics_constants()
{
	memcpy(physics_models, original_physics_models, sizeof(physics_models));
}

// LP addition: get number of physics models (restricted sense)
size_t get_number_of_physics_models() {return NUMBER_OF_PHYSICS_MODELS;}