AutoCAD: Selection

Many AutoCAD commands will prompt you to Select objects. The following are acceptable methods of responding to the Select objects prompt. Each time you add an object to the selection set, it is highlighted (i. e. it appears dashed). When you are finished selecting objects using any one or a combination of these methods, press [Enter] to continue the original command.


 

TO SELECT OBJECTS:

Click on objects one-at-a-time.

OR draw a window around the object(s). AutoCAD uses a click-click method to define a selection window, rather than the standard click-drag-release. “Standard” selection windows are drawn from left to right, and select only those objects completely within the window. “Crossing” windows are drawn from right to left, and select all objects within and contacted by the window.

crossing_standard_01

OR type F (for Fence), and draw a selection line (a “fence”). Like a crossing window, a fence selects any objects it touches. This method is useful for making precise selections in restricted areas.

OR type P (for Previous). This selects whatever object or objects were previously selected.

OR type L (for Last). This selects whatever individual object was last selected or created.

OR type U (for Undo). Deselects the last object(s) selected. Use this if you make a mistake while defining a complex selection set.

OR type ALL. Selects everything in the current space.

OR type R (for Remove). Switches the selection mode from “adding” to “removing”. Type A (for Add) to switch back. Use this function while defining a complex selection set.


PRESELECTING OBJECTS:

It is possible to preselect objects before issuing commands. This technique is frequently useful in 3D (three-dimensional) work, but it can be used in 2D as well.

To preselect an object or objects, click [esc] two or three times in succession, and then either click on objects one at a time or window several objects at once. As you preselect more objects, they display highlighted (i. e. dashed) with grips. Grips are like “handles” at object corners and other critical points. You can click on highlighted grips to stretch and move objects.

After an object has been preselected, you can issue any modifying command (such as ERASE, MOVE, COPY, etc.).

To clear preselected objects from the selection set, click [esc] two or three times in succession.

Advertisements

Photoshop: Selection

Photoshop allows you to define areas upon which you will apply a tool or command. The act of defining such an area is called selection. The simplest selection tool is the marquee, or rectangular selection tool.


USING THE MARQUEE SELECTION TOOL:

1.  Select the Rectangular Marquee Tool (upper-left-hand corner of the tools palette).

2.  Drag the mouse within the image to draw a rectangular area.

3.  Apply one of the Image > Adjust tools (such as Image > Adjust > Color Balance) to see its effect.

4.  Choose Select > None to clear the selection boundary.


THE LASSO TOOLS:

The lasso tool makes freely curved selections and the polygonal lasso makes polygonal selections.


THE MAGIC WAND TOOL:

The magic wand tool selects adjacent pixels with similar levels of brightness. In the options palette (along the top of the screen), you can set the tolerance of the wand, from 0 (highly discriminating) to 255 (does not discriminate between different values).

Using the magic wand tool:

1.  Choose the magic wand tool from the toolbar. In the options palette, set the tolerance to 30 or 40.

2.  Click within an area of solid color in your image.

3.  Apply one of the Image > Adjust tools to see its effect.

4.  Choose Deselect from the Select menu and then repeat the above steps with different values for tolerance.


SELECTION TOOLS UNDER THE SELECT MENU:

Select > All  selects the entire image.

Select > Deselect  deselects everything.

Select > Reselect reselects the last selection.

Select > Inverse selects any deselected areas while unselecting any selected areas.

Select > Color Range produces similar results as the Magic Wand followed by Select > Similar, although Color Range gives a greater degree of control.

Select > Modify > Border selects a border of specified width along the current selection boundary.

Select > Modify > Feather makes the selection edges soft rather than sharp.

Select > Grow enlarges any selection(s) to include adjacent areas with similar colors.

Select > Similar selects pixels similar in brightness to the currently selected pixels.

Select > Transform Selection allows you to stretch, distort, or rotate a selection boundary.


MOVING AND COPYING SELECTIONS.

Use the Move tool (upper right-hand corner of the Tools palette) to move or copy selected areas. To move selected pixels, choose the move tool and drag the selection with the mouse. To copy, hold Alt while dragging the selection. Hold the Shift key down to constrain the movement of the mouse to horizontal, vertical, or 45 degree motion.


DISTORTING SELECTIONS.

Options under Edit > Transform are useful for scaling, rotating, or otherwise transforming selected pixels. To accept a transformation, press Enter.

To distort a rectangular selection:

1. Use the marquee tool to select a rectangular area.

2. Choose Edit > Transform > Distort. You will see “handles” appear at the corners and sides of the selected area.

3. Use the mouse to move one or more of the corner handles. The selected area will distort to the modified boundary. Press Enter to complete the action.


SAVING SELECTIONS.

Once a selection is defined, it can be saved for later use. (Note that what is being saved is not the content of the selected area, but the shape and quality of the selection border.)

Selections are saved in Channels. Channels are simply grayscale images that correspond to the overall shape of your Photoshop image. The level of gray in a channel corresponds to the “amount” of selection – completely black areas are 100% unselected, and completely white areas are 100% selected.