Reduce memory usage

[gongminmin]

The memory consuming (including CPU and GPU memory) is too high for mobile devices. Reduce it by share buffers/textures, and so on.

[gongminmin]

Reduce texture levels width/height/depth variables in changeset be31468b8b018ea79d6636f7974e09aa9c710942.

[gongminmin]

Updated in changeset 578e05152af8f4e315839f2ead681300b1b89805.

[gongminmin]

Updated in changeset 543b8c4e71c5d57bdd3c7fff435a01a9d577293e.

[gongminmin]

Update in changeset a9eeab6b9f0c826d36c5ab310b580966833d13c0.

[gongminmin]

Updated in changeset bd985c9cdca8375414736154d7c465f9b48bf7d1.

[gongminmin]

Updated in changeset ce7caef65fcdd11b76f4b98fe90f8a3df8240019.