glClearAccum - specify clear values for the accumulation
buffer

glClearAccum
	glClearAccum(red, green, blue, alpha) -> None

void glClearAccum( GLfloat red,
                   GLfloat green,
                   GLfloat blue,
                   GLfloat alpha )

red, green, blue, alpha
                      Specify	the red, green,	blue, and
                      alpha values used when the
                      accumulation buffer is cleared.	 The
                      initial	values are all 0.

glClearAccum specifies the red, green, blue, and alpha
values used by glClear to clear the accumulation buffer.

Values specified by glClearAccum are clamped to the range
[-1,1].

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

glGet	with argument GL_ACCUM_CLEAR_VALUE

glClear