gluPerspective & gluLookAt Implementation in Android NDK

There is no glu libraries for android ndk, so I need re-implement one for it. After some time research, I grab some ideas and re-implement glPerspective and gluLookAt function. Both of them works pretty well on PC and android.

 

gluPerspective Implementation

void xgluPerspective( float fovy, float aspect, float near_clip, float far_clip )
{
    const double PI = 3.1415926;
    double TWOPI_OVER_360 = 2.0 * PI / 360.0;
    float half_height = near_clip * (float)tan( fovy * 0.5 * TWOPI_OVER_360 );
    float half_width = half_height * aspect;

#ifdef WIN32
    glFrustum( -half_width, half_width, -half_height, half_height, near_clip, far_clip );
#elif defined(CK_ANDROID)
    glFrustumf( -half_width, half_width, -half_height, half_height, near_clip, far_clip );
#endif
}

 

gluLookAt Implementation

void xgluLookAt (
                        float eyex, 
                        float eyey, 
                        float eyez, 
                        float centerx, 
                        float centery, 
                        float centerz, 
                        float upx, 
                        float upy, 
                        float upz)
{
    vector3_t forward(centerx - eyex, centery - eyey, centerz - eyez);
    vector3_t up(upx, upy, upz);

    forward.Normalize();

    vector3_t side = forward ^ up;
    side.Normalize();

    up = side ^ forward;

    float m[4][4];

    m[0][0] = side[0];
    m[1][0] = side[1];
    m[2][0] = side[2];
    m[3][0] = 0.0f;

    m[0][1] = up[0];
    m[1][1] = up[1];
    m[2][1] = up[2];
    m[3][1] = 0.0f;

    m[0][2] = -forward[0];
    m[1][2] = -forward[1];
    m[2][2] = -forward[2];
    m[3][2] = 0.0f;

    m[0][3] = 0.0f;
    m[1][3] = 0.0f;
    m[2][3] = 0.0f;
    m[3][3] = 1.0f;
    
    glMultMatrixf(&m[0][0]); 
    
    glTranslatef(-eyex, -eyey, -eyez);
}