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# Selecting Objects For Editing

To select a displayed object for editing, press the object illuminate button or select ``Object illum'' from the ***BUTTON MENU***. The object selection is a two step process.

Whenever an object is displayed (using the e command), all paths in the object's hierarchy are traversed recursively, accumulating the transformation matrices. When the bottom of the path (a solid) is encountered, the accumulated transformations are applied to the solid's parameters and the solid is drawn. Thus every solid displayed is really a path ending with that solid. If the object has been displayed using the E command, the same procedure is followed, but only until a region is encountered. Then all members of the region have the accumulated transformations applied and the region is then ``evaluated'' and drawn.

In the first step of the object selection process, the path is selected. Again, the data tablet is divided in as many horizontal sections as there are paths drawn. The path (solid or evaluated region) corresponding to the horizontal section the pen/mouse is located in will be illuminated (brighter on B/W displays and white on color displays). This complete path is also listed on the display. When the pen/mouse is pressed the illuminated path is selected.

In the second step, a member of the selected path is chosen. All editing will then be applied to this member. The tablet is divided into as many horizontal sections as there are path members. The word ``[MATRIX]'' is used to illuminate path members and will appear above the member corresponding to the location of the pen/mouse. Pressing the pen/mouse when the desired path member is ``illuminated'' will put MGED in the object edit state. The editing will be performed on the path member selected.

If a solid is located at the bottom of this path, it becomes the key solid and its vertex becomes the key point. If an evaluated region is at the bottom of the path, the center of this region becomes the key point. All object editing is done with respect to this key point.

The object editing features can be invoked in any order and at any time once an object has been selected for editing. During object editing, any of the viewing features, such as changing views, zooming, and slewing, can be used, and in fact, are usually quite useful. Again, the only way to exit the object editing mode is to ``accept'' or ``reject'' the editing. If the ``reject'' button is pressed (or selected from the edit menu), the object will return to its pre-edit state. If the ``accept'' button is pressed (or selected from the edit menu), the data base will be changed to reflect the object editing performed.

Next: Object Edit State Up: MGED EDITING FEATURES Previous: Combination Editing (OBJECT