GL_AMD_stencil_operation_extended http://www.opengl.org/registry/specs/gl/AMD/stencil_operation_extended.txt GL_AMD_stencil_operation_extended GL_SET_AMD 0x874A GL_REPLACE_VALUE_AMD 0x874B GL_STENCIL_OP_VALUE_AMD 0x874C GL_STENCIL_BACK_OP_VALUE_AMD 0x874D void glStencilOpValueAMD (GLenum face, GLuint value)