DESCRIPTION OF OPERATIONS

INDEX


POSSIBLE OPERATIONS

In this section, we'll present the operations related with objects, once these have been created. Some operations can't be applied to certain objects. So some objects have more operations than others. Even, some operations are specific of a unique kind of object. First, we'll present the operations available for the user. Afterwards, we'll present an abstract of the operations available for each object. But, previous to that, we must state a not so obvious thing: an object, usually, needs to be selected before any operation can be performed on it. To select an object, after pressing the right button of the mouse, that is, in "neuter" state, the mouse is clicked once over the created object. That makes the color of the object to turn red. Moreover, in most cases, if it is filled with color, after selecting it, it turns transparent. Later on, we'll explain in a greater extent the selection of objects, which is important indeed. The ongoing discussion is about selected objects.

COPY or CLONE.- Every object can be cloned as many times as you like just clicking a button. This copy is made retaining all the atributes of the object in the moment of cloning and can be done in the same way with groups.

GROUPING AND UNGROUPING- We can group either objects or groups, even we can group a single object, a very interesting feature sometimes. A group of objects acts like a single object, that can undergo new transformations. This opens many possibilities, because a very same transformation applied to two equal objects doesn't produce always the same result. For example, if we have two circles, side by side, we select them and we apply the "Perpendicular to screen (that is, Z axis ) Rotation" transformation, we'll see no change, because rotation takes as center of rotation the center of the object (the center of each circle). But if we group them before the transformation, if the rotation angle is 90, the circles will change its position, because the rotation center of the compound "two-circles-grouped" object is the center of the group.

LINE THICKNESS CHANGE- The line-thickness-change-operation is done by pressing the button "+" (increasing thickness) or the button "-" (decreasing thickness). Buttons are by side. An small window let us know which is the actual value of the selected line. There's no other options than increase and decrease. The increasing/decreasing is done by steps of 50 %. It can't be lower than 0.1 pt (METAGRAF ignores further decreasings).

OBJECTS MOVEMENT.- Pressing over the objects and dragging. It's as easy as that, no further explainations. Groups behave the same way. Besides with afinne transformations (specially in 3-D ) it's possible to move objects too. Finally with the rules (if present) it is possible to move horizontally or vertically all the objects in the canvas, selected or not. This is useful, for example, when we deal with a real big drawing, then we can scroll and continue drawing. It's like the "scrolling function" but without moving the screen, only the drawings, like a transparent paper.

SHAPE TRANSFORMATION-All selected objects that have "marked" points in the corners and borders can be modified at any time, just clicking and dragging these points. This is very useful in certain objects. It's a "must" for adjusting curves.

TYPE LINE CHANGE- Sometimes we may wish dotted lines or special lines. Pressing the button, a window will appear where we'll be able to choose among six different types of lines.

FILLING AND COLOR CHANGE-Pressing the corresponding buttons the color dialog panel is dispayed. This buttons can be the "fill" one, a circle filled in red, or the "contour" one, a palette of colors. Finally, a third button empties the filling of a colour. Such button is necessary because there's not a transparent colour. Alpha channels are troublesome ( and not only in METAGRAF)..

AFINE TRANSFORMATIONS.-There's a whole series of transformations of this kind. All afine transformations allowed by MetaPost and some other that are interesting for 3-D work. They sum up 14, available for the user and the functioning is almost the same always. Most objects can be used with them. These are the available afine transformations that appears when the selecting button is pressed:

  • X ROTATION.
  • Y ROTATION.
  • Z ROTATION
  • ANY-PREDEFINED-AXIS ROTATION
  • X SHEAR
  • Y SHERA
  • Z SHEAR
  • GENERAL SCALING
  • X SCALING
  • Y SCALING
  • Z SCALING
  • X TRANSLATION
  • Y TRANSLATION
  • Z TRANSLATION

The origin (0,0) is at upmost-leftmost corner of the canvas. The X axis goes from left to right, horizontally. The Y axis goes from top canvas to the bottom. The Z axis goes from origin towards the wall behind the monitor /CRT screen, that is, in the opposite direction of user. It's a right-turning (dextrogirum) axis.

(The text processing operations will be dealt in its own section, not here).

All transformations (with the exception of the rotation around a special axis) use the center of the object as its center, that is , that center behaves like the origin of coordinates. It's like the origin would move into the center of the object and the transformation is done in the axis, and then the axis return back to their corner. (in fact METAGRAF does that internally). Only the PREVIOUSLY-DEFINED-AXIS ROTATION doesn't take such center as has been said.


INDEX