﻿ GhettoBirds游戏源代码(类似愤怒的小鸟）源代码:glu.c
```//
// cocos2d (incomplete) GLU implementation
//
// gluLookAt and gluPerspective from:
// http://jet.ro/creations (San Angeles Observation)
//
//

// Only compile this code on iOS. These files should NOT be included on your Mac project.
// But in case they are included, it won't be compiled.
#import <Availability.h>
#ifdef __IPHONE_OS_VERSION_MAX_ALLOWED

#import <OpenGLES/ES1/gl.h>
#import <math.h>
#import "../../Support/OpenGL_Internal.h"
#include "glu.h"

void gluPerspective(GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar)
{
GLfloat xmin, xmax, ymin, ymax;

ymax = zNear * (GLfloat)tanf(fovy * (float)M_PI / 360);
ymin = -ymax;
xmin = ymin * aspect;
xmax = ymax * aspect;

glFrustumf(xmin, xmax,
ymin, ymax,
zNear, zFar);
}

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 = (float)sqrtf(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]);
if (mag) {
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];

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

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

mag = (float)sqrtf(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) = 0.0f;
M(1, 0) = y[0];
M(1, 1) = y[1];
M(1, 2) = y[2];
M(1, 3) = 0.0f;
M(2, 0) = z[0];
M(2, 1) = z[1];
M(2, 2) = z[2];
M(2, 3) = 0.0f;
M(3, 0) = 0.0f;
M(3, 1) = 0.0f;
M(3, 2) = 0.0f;
M(3, 3) = 1.0f;
#undef M

glMultMatrixf(m);

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

#endif // __IPHONE_OS_VERSION_MAX_ALLOWED
```
﻿