USING THE SLIDERS
In what follows it will be explained in detail the way of working with the Sliders and specially with the principal one. This one is the biggest, over the drawing-panel with four small buttons at its right.
As has been said before, this slider is connected with the "transformation-button", the one with the thick, short, vertical arrow. The way of using the slider is very similar for all the transformations with some exceptions to make the work easier and simpler. So, lets see how the slider must be used with every transformation, and according with the order that appears in the "transformation-panel" as it is launched.
ROTATIONS
The first four transformations available are related with rotations. For those, the use of the slider is very simple as it is graduated by default in degrees, from 0 to 180. Nevertheless, this values can be extended without limitations. For doing that, it is necessary to use the four small buttons at right, so now the function of this four buttons will be explained:
SHEAR.
For this kind of transformation, the value introduced with the slider is the "percentage" of shear in the direction choosen related with the perpendicular one. So, if the value "X_Shear" is selected and the slider is placed over the number 30, the transformation will be a shear in the X-direction of a 30% of the value of the Y coordinate (referred to the center of the object or group of objects) at every point. Now, it is needed to clarify that, unless in special situations, all the affine transformations are done considering the geometrical center of the object or group of objects as the origin of coordinates (which is the only reasonable way of doing it). We can see that in the upper part of the image (negatives "Y-coordinates") the "X-coordinate" has been moved a 30% of its Y-Coors. value to the left. The same, but opposite, at the bottom part. SHEAR is a fine transformation and very interesting for matters related with text.
CHANGE OF SCALE
Without any doubt, this is the most used transformation. It is extremely versatile as it serves for many purposes. It is of continuous use with "special" text but also when we want to make some use of a "zoom" function or when our drawing is small and difficult. In this last case, the best solution is to work at a bigger scale and, when finished, to reduce the image. For all those reasons, it is the transformation chosen by default when the "transform-panel" appears. The Zoom-button, lately implemented, just uses this capability to zooming objects. (Nevertheless something must be said related with zooming. In its present state, zooming is NOT a strong point in METAGRAF, and it must be used with care. A big problem is that the lines that support text will not be changed in position, so zooming drawings with text can have not very nice results. BEWARE!).
The big Slider works in the same way as with SHEAR, so in percentage. If the slider-button is placed over the number 100 and then the transformation is done, nothing changes. As the biggest number in the scale is 180, it is usual to make use of the buttons at right (most of all in 3-d). Those buttons works in a cumulative way. So if an increase of four times is wanted, after placing the ruler over the number 100 the button "x2" must be clicked twice. Over the small window SCALE can be seen the real value; in this case 400.
It is possible to use the change of the scale only in one direction, for instead the X or Y (the Z direction has no meaning in 2-D). In that case, the object or group of objects will be distorted in the direction choose my the corresponding percentage. TRANSLATION.
This is not a very useful transform in normal use. It is a lot simpler to move the objects directly selecting them and dragging the mouse. The work of the slider is the simplest as the objects are moved by default the same amount in unities as it is written on the scale. On another cases, as working in 3-D it can be useful when moving in directions perpendicular to the screen, but we will speak about that later on. One thing must be said about "unities". The METAGRAF unity is the pixel, and working with a resolution of 1024x768, it means that one pixel is 0.25 mm. We will finish this short chapter with a reference to the other smaller sliders. After considering the "pro" and "cons", I have decided to supress them until the 3D capabilities will be available. For many people, more space is a must.
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The "Y_Shear" as can be thought, is exactly the same idea, changing their coordinates. The "Z_Shear" has no meaning in 2-D.
We can see the result of a "X_Shear" of a value equal to 30% now. Here, is the object before shearing it, and here is the object after the transformation.