PRELUDE Tutorial begin2: Exploring the details - co-ordinate system representation
In this tutorial you will learn:
- what is the Right-Hand Rule as applied to the co-ordinate system representation,
- how the 'CAMERA0' object controls this, and
- how to change the attributes of this object to get a different representation of the co-ordinate axes.
The first beginner's tutorial (begin1) was rather long, because it described the main components of the Prelude window, and gave preliminary information about the 'gateways' concept and how to start working within the 'Beginner' gateway.
Other tutorials of the 'Beginner' series will provide a new user with information on a single subject only, to facilitate future work with the Prelude Editor.
You can skip this tutorial or any other to return to them when you feel the need.
As you can judge by the title, this tutorial (begin2) is dedicated to co-ordinate system representation.
- First activate PRELUDE in any possible way described in the tutorial 'begin1'.
- Replace 'case0' by typing in the white space, say, 'tut_2', or
any other character string (but WITHOUT BLANK SPACES).
- Click on 'Load Gateway' and then select 'Beginner' to see in the Graphics window the domain limited by a red-outlined box and its co-ordinate system with the origin placed in the bottom distant corner of the domain.
- Click on the 'object tree' icon
toolbar to display all objects inside the domain.
Why are the co-ordinate system axes displayed in such a way? Z-axis is directed upwards, X-axis points to the left and Y-axis - to the right. Is it the only possible way to represent the axes object?
- The answers to both questions can be obtained through the 'Right-Hand Rule'. The default representation of the co-ordinate system in PHOENICS parlance is the Right-Hand one, according to the following picture.
It signifies that the index finger of the right hand points to Z-direction, the thumb - to Y and the middle finger points to X.
- However, it is true only if the observer's eye is in front of this picture and distanced from the origin. The role of the observer's eye is played here by the object which is called CAMERA0.
Let us discuss how the the co-ordinate system representation will vary with the CAMERA0 position.
- Check that the 'CAMERA0' object is selected in the object tree (the sign of this are the words 'Selected CAMERA0 Attached to Domain' in the top right part of the graphics window). Otherwise first click on 'CAMERA0' in the object tree.
- Click on on the 'red-tick' icon to reveal its attributes, mainly its position.
As you can see, to have such representation of the co-ordinate system, co-ordinates of the point where the 'CAMERA0' object should be placed (although dependent on the domain) are positive values.
- Let us introduce the sign '-' to the X-co-ordinate box, leaving all others unchanged. In this case we shall have the following picture.
CAMERA0 is now looking at the domain from the negative part of the X-axis and the origin is closer to it than the X-axis arrow.
- Introduce minus to the Y-co-ordinate box and you will get what follows.
CAMERA0 in this picture is looking exactly at the right angle side from the origin.
Please note that each time when you make changes in co-ordinate boxes, you must click on some other box to activate these changes.
- Now for the sake of consistency introduce minus to the Z-co-ordinate box to get the picture like this.
The above changes have the result that X and Y-axes changed their place as compared with the first picture.
You may proceed experimenting in this direction, however each time representation of the co-ordinate system will obey the Right-Hand Rule, dependent on the CAMERA0 location.