glGenerateMipmap

glGenerateMipmap: man3/glGenerateMipmap.xml

glGenerateMipmap generates mipmaps for the texture attached to target of the active texture unit. For cube map textures, a GL_INVALID_OPERATION error is generated if the texture attached to target is not cube complete. Mipmap generation replaces texel array levels level base + 1 through q with arrays derived from the level base array, regardless of their previous contents. All other mimap arrays, including the level base array, are left unchanged by this computation. The internal formats of the derived mipmap arrays all match those of the level base array. The contents of the derived arrays are computed by repeated, filtered reduction of the level base array. For one- and two-dimensional texture arrays, each layer is filtered independently.