glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_COMPARE_MODE,GL_COMPARE_R_TO_TEXTURE); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_COMPARE_FUNC,GL_LEQUAL); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_FAIL_VALUE_ARB, 0.5);