libfbx-3d.c

libfxb是linux下只写操作framebuffer的一个轻量级的库。

/*
 *  libfbx-3d.c -- 3D Drawing and Calculation Functions
 *  (C)opyright 2000-2001 U4X Labs
 *
 *  Written by: Mike Bourgeous <[e-mail]>
 *              Sat Sep 2 17:51:53 EDT 2000
 *
 *  $Id: libfbx-3d.c,v 1.5 2001/01/01 08:46:17 lethal Exp $
 *
 *       Originally part of fbgraph.c, now separate.  Responsible 
 *  for drawing 3D pixels, calculating 3D projections, and other
 *  3D drawing or calculation functions.
 *
 *  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 <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <signal.h>
#include <time.h>
#include <math.h>
#include <linux/fb.h>
#include <linux/kd.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/user.h>
#include <termios.h>
#include <ctype.h>
#include <libfbx/libfbx.h>

float view_angle, view_width, view_height, view_scalar_x, view_scalar_y;
int view_offset_x, view_offset_y;

/*
 * Function:	fb_set_viewport()
 * Arguments:	The viewing angle of the 3D camera in degrees.
 * Returns:	None
 * Description:	Sets the viewing angle used for projections done
 * 		by the 3D projection routines.
 */
void fb_set_viewport(float angle, int width, int height)
{
        view_angle = angle;
        view_width = width;
        view_height = height;

        view_scalar_x = (float)(width / 2);
        view_scalar_y = -(float)(height / 2);

        view_offset_x = width / 2;
        view_offset_y = height / 2;
}

/*
 * Function:	fb_project_3d()
 * Arguments:
 * Returns:	None
 * Description:
 */
void fb_project_3d(float x, float y, float z, int *u, int *v)
{
	/* 
	 * Hopefully two multiplications are less 
	 * expensive than one division.
	 */
        float invz = 1.0 / z;

        *u = (int)(view_scalar_x * x * invz) + view_offset_x;
        *v = (int)(view_scalar_y * y * invz) + view_offset_y;
}

/*
 * Function:	fb_putpixel_3d()
 * Arguments:	x, y, and z positioners, rgb values,
 * 		surface to work on.
 * Returns:	None
 * Description:	Plots a pixel in 3d space with rgb values
 * 		on surface.
 */
void fb_putpixel_3d(float x, float y, float z, 
                           int r, int g, int b, 
                           fb_surface *surface)
{
	int u, v;
	
	if (z <= 0)
		return;
	
	u = (int)((float)(surface->width / 2) * 
                         (x / z)) + surface->width / 2;
	v = (int)((float)(surface->height / -2) * 
                         (y / z)) + surface->height / 2;

	fb_putpixel(u, v, r, g, b, surface);
}