Fixed why the depth(gl_FragCoord.z is always 1)! It'
Revert "Fixed why the depth(gl_FragCoord.z is always 1)! It'"

This reverts commit bdf4465688a7037edb0a7ca2b9e90e72fc1ea993.
Fixed why gl_FragCoord.z depth is always 0.998 ~ 1.0.

Fixed why gl_FragCoord.z depth is always 0.998 ~ 1.0.

It was mathematical precision problem.
Read (12.050 Why is my depth buffer precision so poor?)
at :+1:
http://www.opengl.org/archives/resources/faq/technical/depthbuffer.htm