OpenGL Es 2 texture zooming issue - ios

Question

i am working on OpenGL ES 2.0 for my project,what i m trying to do is just give auto zoom of the texture by giving scale value to model matrix.But the problem is,while zooming the texture the edges of texture not maintain the smooth motion instead the edges move step by step motion...can any one give me the solution....
(void)render:(CADisplayLink*)displayLink {
_currentScale++;
glClearColor(0, 104.0/255.0, 55.0/255.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDisable(GL_DEPTH_TEST);
GLKMatrix4 aspect = [animations getActualScaleForImage:inputImage.size withPortSize:CGSizeMake(self.frame.size.width, self.frame.size.height)];
aspect = GLKMatrix4Scale(aspect,1 + (_currentScale/3000), 1 + (_currentScale/3000) , 0);
glUniformMatrix4fv(_modelViewUniform, 1, 0, aspect.m);
glViewport(0, 0, self.frame.size.width, self.frame.size.height);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D,_backGroundTxe);
glUniform1i(_textureUniform, 0);
glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));
glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), GL_UNSIGNED_BYTE, 0);
[_context presentRenderbuffer:GL_RENDERBUFFER];
}
This is my render function

Answer 1

If I have understood your description, it sounds like you need to adjust your texture filtering.
While _backGroundTxe is still bound during the process where you first create it try adding:
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
Alternatively, if you want the texture to look smooth when it zooms out far, you may want to try this instead:
glGenerateMipmaps(GL_TEXTURE_2D);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
This is a nice introduction to OpenGL texture filtering: http://www.learnopengles.com/android-lesson-six-an-introduction-to-texture-filtering/ It's for Android/Java, but it's trivial to translate it to iOS/C++, just omit all the "GLES20."