libfbx-2d.c

libfxb是linux下只写操作framebuffer的一个轻量级的库。

/*
 *  libfbx-2d.c -- 2D Movement and Animation Functions
 *  (C)opyright 2000-2001 U4X Labs
 *
 *  Written by: Kenneth Mills <[e-mail]>
 *              Tue Dec 12 15:32:09 CST 2000
 *
 *  Updated by: Paul Mundt    <[e-mail]>
 *              Wed Dec 20 20:43:15 EST 2000
 *
 *              Michael Bourgeous <[e-mail]>
 *              Fri Dec 22 22:53:03 MST 2000
 *
 *  $Id: libfbx-2d.c,v 1.8 2001/01/01 08:46:17 lethal Exp $
 *
 *       libfbx-2d.c has functions to assist programmers in animating
 *  images and other objects using libfbx.
 *
 *  See ChangeLog for modifications, CREDITS for credits.
 *  			
 *  All source herein is copyright U4X Labs and its original author. 
 *  Any code modifications or additions are (C)opyright the original 
 *  author and U4X Labs respectively.
 *
 *  libfbx is free software; you can redistribute it and/or modify it 
 *  under the terms of the GNU Lesser General Public License as 
 *  published by the Free Software Foundation; either version 2.1 of 
 *  the License, or (at your option) any later version.
 *
 *  libfbx 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 Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with libfbx; if not, write to the Free Software 
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 *  USA
 */
#include <libfbx/libfbx.h>
#include <math.h>

/*
 * Function:    fb_move_object() 
 * Arguments:   Speed, radians, x, y coords.
 * Returns:     None.
 * Description: Moves a vector along a 2d plane
 */

void fb_move_object(float speed, float radians, float *x, float *y)
{	
	*x += speed * cos(radians);
	*y += speed * sin(radians);
}

/*
 * Function:    fb_get_rad()
 * Arguments:   Beginning and ending x, y coords.
 * Returns:	Radian from first to second point.
 * Description: Determines a radian from two specific points.
 */
float fb_get_rad(float x1, float y1, float x2, float y2)
{
	float rad, slope, t;

	t = 0.01745;
	
	if ((fabs((x2-x1)))>=(fabs((y2-y1)))) { //x
		slope = (y1 - y2) / (x1 - x2);
		if (x1<=x2)
			rad=(slope < 0.78539)? t * slope : 5.49778 + (t * slope); //right
		else
			rad = 2.35619 + (t * slope); //left
	} else { //y
		slope=(x1 - x2) / (y1 - y2);
		rad=(y1<=y2)? 3.92699 + (t * slope) /*down*/: 0.78539 + (t * slope); //up
	}
	return rad;
}

/*
 * Function:    fb_get_angle()
 * Arguments:   Beginning and ending x, y coords.
 * Returns:     Angle.
 * Description: Measures angle between first and second
 *              x, y points.
 */
float fb_get_angle(float x1, float y1, float x2, float y2)
{
	return (fb_get_rad(x1, y1, x2, y2) / (PI / 180.0));
}