glClearAccum.3G man page

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

glAccum(3G), glClear(3G)

glAccum.3G(3).