Different valid image due to OpenGL2 zbuffer having a different
resolution or linearity. Having looked into the differences
the zbuffer returns different values in OpenGL2. Sometimes larger
sometimes smaller. Looking at the resulting points it seems
like OpenGL2 is producing points closer to the surface, implying
that it is a more accurate zbuffer. But I hesitate to say that is
definitely the case. Regardless this image corresponds to the
zbuffer values returns from the OpenGL2 backend.

Change-Id: I823c371588c4e390b93e2489ec8a6e54ee73ceb5