3d - OpenGL ES 2.0 - How to realistically deform a sphere? -

i want design 3d physic engine android application. using opengl es 2.0.

this want :

let's have sphere @ center of device's screen. suppose sphere filled water (like water balloon). because of gravity, expect sphere deformed @ bottom. furthermore, using accelerometer of phone, can shift gravity, changing deformation of sphere.

i have made lot of research, still have no idea how that. don't think it's hard do, way can think of how manually draw, frame frame, different shapes.

is there way of generating deformation, instead of drawing 'by hand' ? maybe using shaders ?

i'm lost right !

thank help.

if want in 3d, in realistic way - has nothing opengl es, , require advanced physics engine. shaders used render results.

unless need simple deformation of 2d picture of 3d sphere, frankly, judging way ask question - hard you.