https://github.com/mattdesl/lwjgl-basics/wiki/GLSL-Versions http://www.shaderific.com/blog/2014/3/13/tutorial-how-to-update-a-shader-for-opengl-es-30 shaders & glsl in swift http://www.swiftgl.org/learn/01-shaders.html
to make object face at camera(billboarding) http://nehe.gamedev.net/article/billboarding_how_to/18011/ http://www.lighthouse3d.com/opengl/billboarding/index.php?billInt
move camera according to the sensor rotation matrix in OpenGL ES 2.0 https://github.com/LiamAttClarke/android-gl-experiment a bit complex code with LibGDX http://mesai0.blogspot.kr/2013/03/outdoorgeo-augmented-reality-camera.html
To understand what happens in OpenGL transform matrix, http://www.thecodecrate.com/opengl-es/opengl-transformation-matrices/ http://www.songho.ca/opengl/gl_transform.html