Basic Drawing - 5

Other transformations.-

In Metagraf it is possible also to scale objects in only one direction, horizontal and/or vertical. This capability joint to the rotation one, allows to produce shear deformations.
In what follows it will be explained how to rotate an object around any point and how to scale it in one or two directions, also relative to any point.
The method that will be explained can be used alone or in conjunction with the simple method explained before. The rotations and/or scalings will be cumulative and so on.
Mg5 allows to place a center-transform point (in short "center-point") on any object, to made a transformation and afterwards to delete it. This point can be moved around the screen, so that the transform will be done having as center point this one.
As almost always, in Metagraf, everything can be done using the mouse or with the keyboard. The "mouse" process to place a center-point on an object is what follows:

A blue cross line will appear in the geometrical center point of the points defining the object (shorter: in regular shapes, "in the center of the object"). The point of intersection is the center-point of the selected object. (If no object is selected, nothing happens).
The center point can be selected as any other point, and, once selected it can be moved anywhere.
The "keyboard-way" of placing a center on a selected object is just to press the INSERT key. Once selected, the center can be moved with the mouse or with the arrow-keys.
Once an object is selected and has a center-point (the center-point can be selected or not), if the ENTER key is pressed once, the object will rotate around its center-point, counterclockwise, one degree.
If the Shift key is pressed, pressing the ENTER key will produce a similar rotation but of a value of five degrees.
If, instead, the Alt key is pressed, pressing the ENTER key will produce a similar rotation but of a value of 0.05 degrees.
In any of the cases just mentioned, pressing the Ctrl key at the same time, will change the sense of the rotation from counterclockwise to clockwise.
If an object is selected and has a center-transform point, pressing the insert key will translate the point to the original place in the center of the object if not already there. The same is true using the mouse and the button for placing centers. A second center-point will not be created.
For scaling an object in both directions, everything said for the rotation is valid but, instead of using the ENTER key, the SPACE key should be used. Each time it is pressed, an increase of 1% will be obtained in the dimensions.
If using the Shift key, the increase will be 5%, and if the Alt key is pressed, 0.1%.
If the Ctrl key is pressed a decreased of the same amounts will be obtained.
To obtain the same amounts of scaling but only in the horizontal direction, the PgUp instead of the SPACE key should be used. The PdDn key produces scales only in vertical direction.
Once the transformation is done, the center-point should be deleted, although not imperatively. It just takes more space in the final file.
To delete the center-point, the simplest way is to press the DEL key that will delete all the existing ones. If just one should be deleted, the object can be selected and the button with the red X over the blue cross, clicked.
The process explained can be used with several objects at the same time, although with different center points its usefulness is doubtful. See the next paragraphs related with groups to learn more useful methods.


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Madrid, January 2006