Adaptive scale filtering: a general method for obtaining shape from texture

Introduces adaptive scale filtering, a general method for deriving shape from texture under perspective projection without recourse to prior segmentation of the image into geometric texture elements (texels), and without thresholding of filtered images. If texels on a given surface can be identified in an image then the orientation of that surface can be obtained. However, there is no general characterization of texels for arbitrary textures. Furthermore, even if the size and shape of texels on the surface is invariant with regard to position, perspective projection ensures that the size and shape of the corresponding image texels vary by orders of magnitude. Commencing with an initial set F/sub O/ of identical image filters, adaptive scale filtering iteratively derives a set F/sub N/ which contains a unique filter for each image position. Each element of F/sub N/ is tuned to the three-dimensional structure of the surface; that is, all image filters in F/sub N/ back-project to an identical shape and size on the surface. Thus image texels of various sizes, but associated with a single spatial scale on the surface, can be identified in different parts of the image. When combined with conventional shape from texture methods, edges derived using F/sub N/ provide accurate estimates of surface orientation. Results for planar surfaces are presented.< >