glClearDepth - specify the clear value for the depth buffer

glClearDepth
	glClearDepth(depth) -> None

void glClearDepth( GLclampd depth )

depth	 Specifies the depth value used	when the depth buffer
       is cleared. The initial value is 1.

glClearDepth specifies the depth value used by glClear to
clear	the depth buffer.  Values specified by glClearDepth
are clamped to the range [0,1].

GL_INVALID_OPERATION is generated if glClearDepth is
executed between the execution of glBegin and	the
corresponding	execution of glEnd.

glGet	with argument GL_DEPTH_CLEAR_VALUE

glClear