DXF is the basic format in which AutoCad handles data (DWG being mainly a binary version of DXF). So the format incorporates the features that AutoCad assigns to objects, and it is different for each AutoCad version. As AutoCad objects have no native material or texture information, there is no fixed way of conveying that via DXF. Rendering applications working as AutoCad plugins (like its own rendering) generally store their information either in an external file or into the XDATA section of the DXF/DWG file. The contents and structure of XDATA is defined by the plugin programmer, so there is no standardized format, and the data stored is useful only to the plugin that originated it.
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