Overview of Drawing

Drawing is the process by which you transform your blank mimics into Menus, Overviews, Process Mimics etc. You can draw in mimic using three different mechanisms.

• Using the Workspace tools, you can create mathematically defined drawing elements (geometric shapes) including rectangles, ellipses, lines, polygons and text. Each element has a wide range of properties that allow you to quickly and easily change the appearance. For example, a rectangle can appear as a button.
• By importing images in particular Windows formats, you can display scanned images, standard Windows’ icons etc.
• Using OLE (Object Linking & Embedding), you can include information created in other applications, such as charts, graphics, and spreadsheet data.

You display the process you are supervising by attaching properties of the drawing elements to the real time value of variable in the variables tree. For example, a polygon representing a valve can change color depending on the valve position. Attaching properties of drawing elements to the real time value of variables is known as animation. Animation is described in a later book.

Using Geometric Shapes

The drawing elements produced by the Workspace tools are defined as a set of co-ordinates plus properties describing color and style. They are, in effect, geometric shapes. The properties of geometric shapes are much easier to change and to attach to the value of variables in the variables tree. The points for and against the use of geometric shapes may be summarized as follows.

For:

• Easy to draw and change.
• Very wide range of possibilities for dynamically changing properties.
• Mimic definition files containing only geometric shapes are very compact.
• Geometric shapes use memory efficiently when they are displayed.

Against:

• Pictures created with just geometric shapes generally are less attractive than those using images.

Using Images

Once an image is created there is very little that can be done to change it dynamically. You cannot, for example, attach an area of an image to a variable so that it changes color according to the value of the variable. The points for and against the use of images may be summarized as follows.

For:

• There are many drawing and paint packages able to produce stunning pictures in image format.
• Images may be created from scanned pictures of real world objects.
• The number of colors that may be displayed in an image is limited only by the capability of the host PC.

Against:

• Images, particularly those with lots of colors, need very large files to store them and use considerable amounts of memory (RAM) when they are displayed.
• Limited possibilities for dynamically changing images according to the value of the variables.

Using OLE Objects

When linking or embedding information from another application, the information is displayed in the mimic in the same form as it would be in the original application. For example, you could display a Microsoft Word document. When you double click on the object in Edit mode the application in which the object was originally created is automatically opened and the object is displayed ready for editing. When you return to the HMI the mimic reflects any changes you have made to the object.

For:

• You can display information in virtually any form as long as there is a Windows application, supporting OLE, capable of editing it.

Against:

• You must use the original application to change the object.
• Very limited possibilities for dynamically changing OLE objects according to the value of the variables.