Hello folks,

I must say, I'm new to OpenGL ES 2.0 and I'm working on Android.
I've written a small vertex shader that implements the scaling and translation of my incoming vertices. Therefor I have a scaling-matrix (mat4 scale) given by
/ sx 0 0 0\
| 0 sy 0 0|
| 0 0 sz 0|
\ 0 0 0 1/
and a translation-vector (vec4 trans) given by:
/tx\
|ty|
|tz|
\1/
so gl_Position = (scale * Vertex) + trans;

but I thought it's easier to give both operations in just one matrix (mat4 proj), so that gpu has only to perform an multiplication and and not a multiplication AND addition. matrix4 looks like that:
/ sx 0 0 tx\
| 0 sy 0 ty|
| 0 0 sz tz|
\ 0 0 0 1/
so gl_Position = Vertex*proj;

Now the problem: the first way coordinate-tranformation works, but when I put both operations together in one martix nothing happens. dont' know what is going wrong? - please help!