Special Modes

Add Text

The "Add text" mode is a multi-purpose mode for almost everything related to displaying text in a view. Here are the main applications of this mode:

• Add plain text: You click at some position in a view. Then an input dialog pops up asking you to input the desired text. When you exit the window, the text is displayed at the position where you clicked.
• Edit text: When you click on an already existing text you will get an editing window that shows the old text. This text can now be changed. After leaving the input window the old text is replaced by the new text.
• Changing a label: When you click on a geometric element you will also get an editing window, now showing the label of that element. You can now input a new label for the element. However, there is a restriction: The label of an element must be unique in the construction. If you try to input an already existing label a warning message is shown and the label remains unchanged.

Texts are more flexible objects than you may think at first. This comes from two important features, docking and referencing:

• Docking:
  Usually a text is located at a certain position relative to the coordinate system of the drawing. When you zoom or translate the view the text will follow the zooming. This is sometimes desired, but sometimes you might want a different effect. Imagine that you have a description text that should always be shown in the upper left corner of the view. Then you should use "docking." In the move mode you pick a text and move it around by dragging the mouse. If you come to a position close to the boundaries of the window you recognize that the text snaps to predefined docking positions. When the text is docked it stays in its position relative to the window.

  It is also possible to dock a text to a point. Drag the text close to the point until the point is highlighted. The text will then consistently stick to the point.

• Referencing:
  Often it is necessary to have changing parameters inside a text. Imagine a text saying: "The distance between A and B is 25 cm". In such a text you usually want to refer to the actual distance between "A" and "B" and not to a fixed string "25". You can do this by referencing the value of a geometric element. If "A" is the geometric element then "@#A" references its value. Moreover, you usually want to mark the fact that the "A" and the "B" in your text are labels. This forces further changes of element names are reported to the text object, and that the displayed text is changed accordingly. You can use "@$A" to refer to a label. If "dist" is the label of the distance object then the above effect would be generated by the following input string:

     The distance between @$A and @$B is @#dist cm.
  	

  In the case of points, lines and conics the "@#" operator refers to the coordinates. So, you can write:

     The coordinates of @$A are @#A.
  	

Altogether you have three possibilities for referring to the data of a geometric element. If element is the name of the label then you access

• the label of the element by @$element,
• the defining algorithm of the element by @@element, and
• the value or position of the element by @#element.

The texts that are then generated are precisely the ones you can see also in the Construction Text" view. The exact representation of the element's value or position can be influenced by the according settings in the "Format" menu.

If you want to include greek characters you can do so by using @ and the name of the character, like in @alpha or @Omega.

Synopsis

Add and edit a text in an Euclidean view.

Caution

So far, texts are only supported in the Euclidean view.

Locus

A locus is the trace of a point under the movement of another point. A locus is defined by three objects:

• The mover, a free element whose movement drives the generation of the locus.
• The road, an element incident to the mover. The mover will be moved along the road.
• The tracer, the element whose trace is calculated and presented as a geometric locus.

The mover, road and tracer must be selected in this order. However, if the mover is either a "Point on line", a "Point on circle", or a "Line through point" then Cinderella automatically recognizes that there is a unique road and selects it for you automatically. You should watch the message line to check which input is required at a certain stage of a construction. Currently the following combinations of mover and road are supported:

• mover = point, road = line: The point moves along the line.
• mover = point, road = circle: The point moves along the circle.
• mover = line, road = point: The line rotates around the point.

A cycloid

Cinderella also supports the selection of a "line" as the tracer. In this case the envelope of the moving line is calculated.

The envelope of light rays in a circular mirror

Loci of elements are real branches of algebraic curves. Cinderella will always try to generate an entire branch.

Synopsis

Generate a geometric locus by selecting a mover, a road and a tracer.

Caution

Sometimes you will notice a short delay when a locus is being calculated. Do not blame your computer or Cinderella (or, even worse, the authors). These delays can be caused by extremely difficult calculations that are necessary to get the correct result (a complete branch of the curve) or the correct screen representation after a movement. We tried our best to speed up these calculations, but there is a (mathematical) limit where we do not want to sacrifice accuracy for speed.

See also

• Animation

Animation

In an animation you do not move the points by yourself; Cinderella does it for you. An animation is defined by a "mover" and a "road", similar to the definition of a locus.

• The mover is a free element whose movement drives the animation.
• The road is an element incident to the mover. During the animation, the mover will be moved along the road.

Either you select the mover and the road in this order, or you click on a locus, which will select the mover and road of the locus. If the selected mover is either a "Point on line", a "Point on circle", or a "Line through point" then Cinderella automatically recognizes that there is a unique road and selects it for you. Currently the following combinations of mover and road are supported:

• mover = point, road = line: The point moves along the line.
• mover = point, road = circle: The point moves along the circle.
• mover = line, road = point: The line rotates around the point.

After you have started the animation an Animation Control panel pops up:

This panel contains 5 buttons and one slider. With the slider you can control the animation rate. The detailed meaning of the buttons is as follow:

• Start the animation.
• Pause the animation.
• Stop the animation.
• Export the animation to an HTML-page.
• Exit the animation.

When an animation is running all other functions of Cinderella are blocked. The only way to leave the animation is to press the "Exit" button.

In HTML-exports of animations which are generated by Cinderella, it is not possible to interactively drag the elements. All animation is done automatically by Cinderella. The export function exports all currently open views to an HTML page. The animation runs simultaneously in all these views. For further information consult the chapter on creating interactive web pages and exercises.

Synopsis

Start an animation by selecting a mover and a road.

See also

• Locus

Add a Segment

This mode is completely analogous to the "Add a line" mode. By a press-drag-release sequence you add two points and a segment joining them. In addition, segments can also be supplied with arrows at one or at both ends. Unlike a line these segments are not active as geometric elements. This means you cannot use them for further geometric constructions (like generating intersections). The segments are purely graphical elements.

There are two reasons why you would use this mode. The first of these reasons is obvious: You want to create an arrow. The second reason is much more subtle. Perhaps you have a construction in which you want to show more than one segment supported by the same line. Since Cinderella does not allow elements to be added more than once there is no chance of having two identical lines. The usual line clipping mechanism of Cinderella is insufficient for this task. To bypass this problem you have the possibility of using segments. To avoid mathematical inconsistencies they are treated as graphical elements with no further geometric functionality.

Drawing an arrow

To draw an arrow you draw a segment, select it, and open the Arrow Editor by choosing the "Properties/Arrow Type" item in the menu.

The Arrow Editor

The Arrow Editor is analogous to the Appearance Editor. Its choices apply to the currently selected segments. You have the possibility of adding an arrow at either end of the segment. Four different types of arrow heads are provided. Two sliders allow you to control the size and the position of the arrow.

Examples of different arrows

Synopsis

Add a segment by a press-drag-release sequence.

Caution

Arrows are currently only supported in Euclidean views. Segments and arrows are purely graphical elements and they cannot be used for further constructions.

See also

• Add a line