ios - OpenGL ES 2.0 Pinch and Zoom -

in opengl es 1.1 on ios used implement pinch , zoom setting field of view using following:

// handles touches events - (ibaction)handlepinchgesture:(uigesturerecognizer *)sender  {     static float startfov=0.0;     cgfloat factor = [(uipinchgesturerecognizer *)sender scale];     uigesturerecognizerstate state;      state=sender.state;      if(state==uigesturerecognizerstatebegan)     {               startfov=[self getfieldofview];     }     else if(state==uigesturerecognizerstatechanged)     {         float minfov=5.0;         float maxfov=12.0;         float currentfov;          currentfov=startfov*factor;          if((currentfov>=minfov) && (currentfov<=maxfov))             [self setfieldofview:currentfov];     }      } 

using pinch gesture this:

// set fulstrum , our field of view window -(void)setclipping {     // near , far front , walls     // fov in degrees     float aspectratio;     const float znear = .1;                      const float zfar = 2000;                         glfloat size;     float scale;      // main screen , define aspect ratio     cgrect frame = [[uiscreen mainscreen] bounds];           aspectratio=(float)frame.size.width/(float)frame.size.height;                        scale=[[uiscreen mainscreen]scale];      // use 2d projection matrix project our 3d 2d     glmatrixmode(gl_projection);                     glloadidentity();     if (m_fieldofview > 75.0) {         m_fieldofview = 75.0;     }     size = znear * tanf(glkmathdegreestoradians (m_fieldofview) / 2.0);       // define pyramid of giza (4 sided pyramid top lopped off on side)     // ... how viewing things     glfrustumf(-size, size, -size/aspectratio, size/aspectratio, znear, zfar);       glviewport(0, 0, frame.size.width*scale, frame.size.height*scale);            // safe go tranformational matrix     glmatrixmode(gl_modelview);              } 

i made simple opengl es 2.0 application , update method looks ( partially ) this:

#pragma mark - glkview , glkviewcontroller delegate methods  - (void)update {      // set frustrum , projection matrix     float aspect = fabsf(self.view.bounds.size.width / self.view.bounds.size.height);     glkmatrix4 projectionmatrix = glkmatrix4makeperspective(glkmathdegreestoradians(65.0f), aspect, 0.1f, 100.0f);     self.effect.transform.projectionmatrix = projectionmatrix; 

i've been scouring web how opengl es 2.0... no avail. how do in 2.0?

multiply first term of glkmatrix4makeperspective factor (a property or class variable) , change factor in gesture recogniser - not different in 1.1 method.

here method call gesturerecogniser. variables starting _ class variables. zoomtouchsensitivity preprocessor define.

-(void)scale:(uitapgesturerecognizer*)sender {       cgfloat scale = _lastscale + (1.0 - [(uipinchgesturerecognizer*)sender scale])*zoomtouchsensitivity;      float newscale = max(0.1, min(scale, 3));     _projectionmatrix = glkmatrix4makeperspective(newscale*glkmathdegreestoradians(45.0f), (float)_screenwidth/(float)_screenheight, 100.0f, 1000.0f);     if([(uipinchgesturerecognizer*)sender state] == uigesturerecognizerstateended) {         _lastscale = newscale;         return;     } } 

note how i'm saving last value of scale once gesture stops, zoom isn't 'reset' everytime.