gluLookAt ()

Quelqu'un m'a demandé une mise en œuvre de gluLookAt () pour OpenGL ES. Je n'ai pas eu un, mais je savais où je pourrais en obtenir un. L' Mesa3D projet est un non-autorisés, open-source compatible OpenGL bibliothèque. Certaines modifications ont été nécessaires pour obtenir cette fonction pour travailler sous OpenGL ES, mais ce n'est, en aucune façon, mon travail - je viens un peu tordu de sorte qu'il serait compiler et exécuter sur OpenGL ES 1.1.

gluLookAt.h

/*
 *  gluLookAt.h
 *
 *  This is a modified version of the function of the same name from 
 *  the Mesa3D project ( http://mesa3d.org/ ), which is  licensed
 *  under the MIT license, which allows use, modification, and 
 *  redistribution
 *
 *  In order to work under OpenGL ES, all instances of GLdouble
 *  had to be changed to GLfloat, and all "d" function calls had
 *  to be changed to the "f" versions.
 *
 *  Original developer's comments have been left in place.
 *
 *  Out of respect for the original authors, this is licensed under
 *  the Mesa (MIT) license. Original license follows:
 *  
 *  -----------------------------------------------------------------------
 *
 *  Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
 *  
 *  Permission is hereby granted, free of charge, to any person obtaining a
 *  copy of this software and associated documentation files (the "Software"),
 *  to deal in the Software without restriction, including without limitation
 *  the rights to use, copy, modify, merge, publish, distribute, sublicense,
 *  and/or sell copies of the Software, and to permit persons to whom the
 *  Software is furnished to do so, subject to the following conditions:
 *  
 *  The above copyright notice and this permission notice shall be included
 *  in all copies or substantial portions of the Software.

 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 *  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 *  BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 *  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 *  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
*/
#import <Foundation/Foundation.h>
#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES1/gl.h>
#import <OpenGLES/ES1/glext.h>

void gluLookAt(GLfloat eyex, GLfloat eyey, GLfloat eyez,
          GLfloat centerx, GLfloat centery, GLfloat centerz,
          GLfloat upx, GLfloat upy, GLfloat upz);

gluLookAt.m

/*
 *  gluLookAt.c
*/

#include "gluLookAt.h"

void gluLookAt(GLfloat eyex, GLfloat eyey, GLfloat eyez,
          GLfloat centerx, GLfloat centery, GLfloat centerz,
          GLfloat upx, GLfloat upy, GLfloat upz)
{
    GLfloat m[16];
    GLfloat x[3], y[3], z[3];
    GLfloat mag;

/* Make rotation matrix */

/* Z vector */
    z[0] = eyex - centerx;
    z[1] = eyey - centery;
    z[2] = eyez - centerz;
    mag = sqrt(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]);
if (mag) {          /* mpichler, 19950515 */
        z[0] /= mag;
        z[1] /= mag;
        z[2] /= mag;
    }

/* Y vector */
    y[0] = upx;
    y[1] = upy;
    y[2] = upz;

/* X vector = Y cross Z */
    x[0] = y[1] * z[2] - y[2] * z[1];
    x[1] = -y[0] * z[2] + y[2] * z[0];
    x[2] = y[0] * z[1] - y[1] * z[0];

/* Recompute Y = Z cross X */
    y[0] = z[1] * x[2] - z[2] * x[1];
    y[1] = -z[0] * x[2] + z[2] * x[0];
    y[2] = z[0] * x[1] - z[1] * x[0];

/* mpichler, 19950515 */
/* cross product gives area of parallelogram, which is < 1.0 for
     * non-perpendicular unit-length vectors; so normalize x, y here
*/

    mag = sqrt(x[0] * x[0] + x[1] * x[1] + x[2] * x[2]);
if (mag) {
        x[0] /= mag;
        x[1] /= mag;
        x[2] /= mag;
    }

    mag = sqrt(y[0] * y[0] + y[1] * y[1] + y[2] * y[2]);
if (mag) {
        y[0] /= mag;
        y[1] /= mag;
        y[2] /= mag;
    }

#define M(row,col)  m[col*4+row]
    M(0, 0) = x[0];
    M(0, 1) = x[1];
    M(0, 2) = x[2];
    M(0, 3) = 0.0;
    M(1, 0) = y[0];
    M(1, 1) = y[1];
    M(1, 2) = y[2];
    M(1, 3) = 0.0;
    M(2, 0) = z[0];
    M(2, 1) = z[1];
    M(2, 2) = z[2];
    M(2, 3) = 0.0;
    M(3, 0) = 0.0;
    M(3, 1) = 0.0;
    M(3, 2) = 0.0;
    M(3, 3) = 1.0;
#undef M
    glMultMatrixf(m);

/* Translate Eye to Origin */
    glTranslatef(-eyex, -eyey, -eyez);

}