Dark Texture in Artworks

摘要

This presentation highlights issues relating to the digital capture printing of 2D and 3D artefacts and accurate colour reproduction of 3D objects.There are a range of opportunities and technologies for the scanning and printing of two-dimensional and three-dimensional artefacts [1]. A successful approach of Polynomial Texture Mapping (PTM) technique, to create a Reflectance Transformation Image (RTI) [2-4] is being used for the conservation and heritage of artworks as these methods are non invasive or non destructive of fragile artefacts. This approach captures surface detail of two-dimensional artworks using a multidimensional approach that by using a hemispherical dome comprising 64 lamps to create an entire surface topography. The benefits of this approach are to provide a highly detailed visualization of the surface of materials and objects. In order to reproduce an object, as a facsimile or replica, the types of files need to be either as a polygonal mesh that describes the contours of the surface, or as a series of 2D layers, which when stacked together form a 3D object. Recent experience has highlighted problems in obtaining good scanning data for object reproduction through additive layer manufacturing (ALM) technologies. In fact a large file does not necessarily lead to a file that contains relevant or quality information. Digital printing technologies have begun to consider colour for 3D printing and 2D texture printing, but this has not been sufficiently considered. Most ALM manufacturers use materials that include, thermoplastics, metal, flexible and non flexible photopolymers and powder, which are body coloured (metallic, neutral resin, white powder), in some technology colour is sprayed to the outside of the object as part of the additive layer process, for example, ZCorp printers employ coloured heads that inkjet a coloured layer to the surface (ZPrinter® 650 contains 5 print heads, including black). With the introduction of 2D ultra violet curing printers, it is possible to begin to add texture to flat surfaces. It is also possible to combine colour and texture to create a surface relief, but the height is limited to approximately 1-2mm due to the restrictions of the head height. The file information to do this is based on a vector format. The questions therefore are how can artworks be reproduced with the benefit of printed texture. Can this texture be incorporated that could be used for example as a method for improving visually impared or to reproduce fine detail such as cracks, brush strokes or impasto to the surface of paintings to provide meaningful information to the conservator or assists the artist in new ways for creativity? [5]. Files generated from scanning are not compatible with 2D printing. How can we begin to develop scanning images and artefacts that can be incorporated for a range of uses rather than a single function? eg. currently there are no common file formats between an image file (JPEG, Tiff, PNG and GIF) vector files (.EPS, .AI .CDR .SVG), 3D stereolithography files (STL, VRML, PLY, 3DS, ZPR).