In AutoCAD 2015, the function of pre-selection of objects when you hover the mouse pointer over them, this function is not always and not for all is convenient and useful. For disabling pre-selection of objects meets the variable
SELECTIONPREVIEW. when calling it from the command line and setting the value to 0, the function of preliminary selection of objects will be disabled .
Quite often there is a need to reduce the size of the AutoCAD DWG file, except for the methods already described in the article, we will consider two more. In AutoCAD, there is a command that allows you to delete Unused blocks in the current file, fonts, layers, etc., which also increase the file size. To call this command, select the File menu, then the Utilities item, the Clear command, in the command window click the «Delete All» button.
Blocks can be used to reduce the size of a DWG file with a large 3D assembly containing duplicate objects (_block command in the Russian version). We place one instance of an object or a group of objects in a block, and use the already created block as the remaining instances. when inserting the next block instance into a file, AutoCAD inserts only a link to it, which significantly reduces the file size .