source: code/branches/wiimote/src/external/wiicpp/wiic/dynamics.c @ 10422

/*
 *    dynamics.c
 *
 *        This file is part of WiiC, written by:
 *              Gabriele Randelli
 *              Email: randelli@dis.uniroma1.it
 *
 *    Copyright 2010
 *              
 *        This file is based on Wiiuse, written By:
 *              Michael Laforest        < para >
 *              Email: < thepara (--AT--) g m a i l [--DOT--] com >
 *
 *        Copyright 2006-2007
 *
 *    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 3 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.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *        $Header$
 */

/**
 *      @file
 *      @brief Handles the dynamics of the wiimote.
 *
 *      The file includes functions that handle the dynamics
 *      of the wiimote.  Such dynamics include orientation and
 *      motion sensing.
 */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>


#include "definitions.h"
#include "wiic_internal.h"
#include "ir.h"
#include "dynamics.h"

/**
 *      @brief Calculate the roll, pitch, yaw.
 *
 *      @param ac                       An accelerometer (accel_t) structure.
 *      @param accel            [in] Pointer to a vec3b_t structure that holds the raw acceleration data.
 *      @param orient           [out] Pointer to a orient_t structure that will hold the orientation data.
 *      @param rorient          [out] Pointer to a orient_t structure that will hold the non-smoothed orientation data.
 *      @param smooth           If smoothing should be performed on the angles calculated. 1 to enable, 0 to disable.
 *
 *      Given the raw acceleration data from the accelerometer struct, calculate
 *      the orientation of the device and set it in the \a orient parameter.
 */
void calculate_orientation(struct vec3f_t* in, struct ang3f_t* out) {
        float x, y, z;

        /*
         *      roll    - use atan(z / x)               [ ranges from -180 to 180 ]
         *      pitch   - use atan(z / y)               [ ranges from -180 to 180 ]
         *      yaw             - impossible to tell without IR
         */

        /* yaw - set to 0, IR will take care of it if it's enabled */
        out->yaw = 0.0f;

        /* find out how much it actually moved and normalize to +/- 1g */
        x = in->x;
        y = in->y;
        z = in->z;

        /* make sure x,y,z are between -1 and 1 for the tan functions */
        if (x < -1.0f)                  x = -1.0f;
        else if (x > 1.0f)              x = 1.0f;
        if (y < -1.0f)                  y = -1.0f;
        else if (y > 1.0f)              y = 1.0f;
        if (z < -1.0f)                  z = -1.0f;
        else if (z > 1.0f)              z = 1.0f;

        /* if it is over 1g then it is probably accelerating and the gravity vector cannot be identified */
        if (abs(in->x) <= 1.0) {
                /* roll */
                x = -RAD_TO_DEGREE(atan2f(x, z));

                out->roll = x;
        }

        if (abs(in->y) <= 1.0) {
                /* pitch */
                y = RAD_TO_DEGREE(atan2f(y, z));

                out->pitch = y;
        }
}


/**
 *      @brief Calculate the gravity forces on each axis.
 *
 *      @param ac                       An accelerometer (accel_t) structure.
 *      @param accel            [in] Pointer to a vec3b_t structure that holds the raw acceleration data.
 *      @param gforce           [out] Pointer to a gforce_t structure that will hold the gravity force data.
 */
void calculate_gforce(struct accel_t* ac, struct vec3b_t* accel, struct gforce_t* gforce, int smooth) {
        float xg, yg, zg;

        /* find out how much it has to move to be 1g */
        xg = (int)ac->cal_g.x;
        yg = (int)ac->cal_g.y;
        zg = (int)ac->cal_g.z;

        /* find out how much it actually moved and normalize to +/- 1g */
        gforce->a_vec.x = ((int)accel->x - (int)ac->cal_zero.x) / xg;
        gforce->a_vec.y = ((int)accel->y - (int)ac->cal_zero.y) / yg;
        gforce->a_vec.z = ((int)accel->z - (int)ac->cal_zero.z) / zg;
        
        if(smooth) {
                apply_smoothing(gforce, ac->st_alpha);
        }
        else {
                gforce->vec.x = gforce->a_vec.x;
                gforce->vec.y = gforce->a_vec.y;
                gforce->vec.z = gforce->a_vec.z;                
        }
}


/**
 *      @brief Calculate the angle and magnitude of a joystick.
 *
 *      @param js       [out] Pointer to a joystick_t structure.
 *      @param x        The raw x-axis value.
 *      @param y        The raw y-axis value.
 */
void calc_joystick_state(struct joystick_t* js, float x, float y) {
        float rx, ry, ang;

        /*
         *      Since the joystick center may not be exactly:
         *              (min + max) / 2
         *      Then the range from the min to the center and the center to the max
         *      may be different.
         *      Because of this, depending on if the current x or y value is greater
         *      or less than the assoicated axis center value, it needs to be interpolated
         *      between the center and the minimum or maxmimum rather than between
         *      the minimum and maximum.
         *
         *      So we have something like this:
         *              (x min) [-1] ---------*------ [0] (x center) [0] -------- [1] (x max)
         *      Where the * is the current x value.
         *      The range is therefore -1 to 1, 0 being the exact center rather than
         *      the middle of min and max.
         */
        if (x == js->center.x)
                rx = 0;
        else if (x >= js->center.x)
                rx = ((float)(x - js->center.x) / (float)(js->max.x - js->center.x));
        else
                rx = ((float)(x - js->min.x) / (float)(js->center.x - js->min.x)) - 1.0f;

        if (y == js->center.y)
                ry = 0;
        else if (y >= js->center.y)
                ry = ((float)(y - js->center.y) / (float)(js->max.y - js->center.y));
        else
                ry = ((float)(y - js->min.y) / (float)(js->center.y - js->min.y)) - 1.0f;

        /* calculate the joystick angle and magnitude */
        ang = RAD_TO_DEGREE(atanf(ry / rx));
        ang -= 90.0f;
        if (rx < 0.0f)
                ang -= 180.0f;
        js->ang = absf(ang);
        js->mag = (float) sqrt((rx * rx) + (ry * ry));
}

/**
 *
 * @brief Apply a smooth factor to accelerometer angles.
 *
 * @param accel         Last acceleration measured and normalized to +/-g.
 * @param gforce        [out] gravity vector after smoothing
 */
void apply_smoothing(struct gforce_t* gforce, float alpha) {
        
        gforce->vec.x = alpha*gforce->vec.x + (1.0-alpha)*gforce->a_vec.x;
        gforce->vec.y = alpha*gforce->vec.y + (1.0-alpha)*gforce->a_vec.y;
        gforce->vec.z = alpha*gforce->vec.z + (1.0-alpha)*gforce->a_vec.z;
}