Design versus drafting
General concepts
Design versus drafting
Design versus draughting

DIAMOND is a design rather than a draughting system. It utilises the computer’s power to "remember" not only a final drawing in terms of the picture as generated by the engineer or draughtsperson, but also the way in which the drawing has been constructed. This includes the way and order in which the drawing was constructed and all the relationships between the various elements placed on it. This information is later used to automatically modify all items that were created dependent or in relation to items modified by the user.

A simple example is the creation of an arc fillet of a given radius between two lines. Most systems treat the created fillet as a normal arc bearing no relation to the line entities selected during its creation. Consequently, subsequent modification of the lines by operations such as ‘move’, ‘rotate’ ‘scale’, ‘stretch’ or ‘transfer’, will leave the fillet isolated and completely detached from the 2 lines used for its original
definition. Similarly, provided the fillet radius can be changed, the fillet will again become detached from the two. In DIAMOND, the consequence of similar operations is an automatic recalculation of the fillet, as if recreated in the newly defined circumstances.

Another example concerns the creation of a mirror image of part of the drawing, or the dimensioning of the entities in it. Most systems allow further modifications of the original geometry but make no attempt to reflect them in the mirror images or associated dimensions. DIAMOND acts differently. A modification made to the original entities will immediately be reflected in their mirror images and associated dimensions. DIAMOND will even reflect, in a similar manner, any modification made to the original mirror axis or axes.

As part of the design facility, DIAMOND facilitates simple handling of parameterised drawings, where required geometry, and their properties, are specified in terms of parameters instead of fixed scalar or angular dimensions. Parameters can be specified in a variety of ways, from constants or simple measurements taken from the existing geometry, to more complex equations including references to other exiting parameters. Again, changing existing parameters will automatically modify associated geometry, as well as the magnitudes of other parameters based on the modified geometry.<

Current items

DIAMOND has the concept of the current entity, which refers to both geometric and administrative items. The current geometric entity is the last item to be created or modified, and can also be a set (or group) of items. The current administration entities are those that are currently in use, for example, the current project and drawing or the menus currently being used.

Most edit operations can be applied to the current entity without the need to select it first. If the chosen edit operation cannot be applied to the current item, then DIAMOND will inform the user accordingly.

Those edit operations that result in the removal of the selected item, for example "delete", can only be applied to the current item by using the current item selection command tilda (or "~").

Edit on the fly

A current mode of operation is maintained whenever possible. Therefore a LINE command issued while in CREATE ARC mode switches the system from arc to line creation, maintaining the important CREATE mode of operation.

Every newly created entity immediately becomes the current item. It can therefore be edited directly after its creation by issuing an edit command with, if required, the "~" option. Once the edit is performed, DIAMOND returns to the important creation mode. If an operation is nominated and an entity implicitly chosen, then DIAMOND will switch to this specified mode of operation and remain there.

A perfect combination

The combination of current mode and current item helps to minimise the number of instructions required to perform draughting tasks.

Once a mode of operation is specified, it can be applied to a series of selected items without an obligation to re-specify the demanded operation. Similarly, if a current item exists, a series of edit operations can be applied to it without the burden of frequent item re-selections.

Saving, saving ...

Parameterised drawings are ideal for the production of any number of variations of the same intrinsic design, without the need to repeat designs or modify a previous one. The same is true with regard to parameterised parts. DIAMOND's steel library contains only fifteen parts - all of them parameterised. This surprisingly tiny library is sufficient to generate symbols required for the display of ‘section’, ‘shaded’ (hatched), ‘outline’, ‘plan’, ‘elevation’ and ‘flange’ views of all standard sizes of universal beams, universal columns, rolled steel joists, universal channels, circular hollow sections, square hollow sections, rectangular hollow sections, equal angle beams, unequal angle beams, castellated universal beams, castellated universal columns, and castellated steel joists. Literally hundreds of different symbols can be created, based on only fifteen parts, all according to the required standard, by a single menu click.

In fact, DIAMOND offers much more. Following any modification of the existing geometry or its parameters, while redefining all the affected entities in light of the new circumstances, it carefully checks the validity of the modified geometry. If DIAMOND discovers during this process that the redefinition of any entities becomes illegal, it will return all items modified so far to their previous stage, thus reducing the chance of design errors.

The above-mentioned examples relate to very simple constructions, but the same principles can be applied to any required design, regardless of its complexity. The power and potential benefits of design facilities become more significant as operations being performed become more elaborate. They allow users to manipulate not only basic entities such as arcs, curves or lines, according to a predefined set of rules, but also newly constructed assemblies behaving according to rules set by the system operator.

DIAMOND fully constructs dependency and relationship information from normal draughting procedures - the process does not require the use of any additional or special commands, nor does it place any limitations on the nature of the assignment that can be carried out. Due to dependency information, DIAMOND is capable of automatically changing a whole design, whenever one of the components on which it was based is subsequently modified. This obviously reduces the time required for creation of new drawings, especially when they are variations of existing ones. It also increases the efficiency of modifying existing drawings, a major part of the work carried out in every design office, and allows operators to test the validity or performance of a design in various circumstances.

Current co-ordinates

The current co-ordinate refers to the last designated position, or the one nearest to an item's selection point, depending on the operation mode.

Current co-ordinates can be end points for lines, control points for curves, hatches and polylines, end and centre points for arcs and sectors, centre points for circles and ellipses, origins for bars, profiles, solids, symbols and texts, end points or annotation origins for dimensions or assigned origins for boundaries, fences and groups.

The current co-ordinate is utilised as the anchor point for operations like scale or rotate, or reference point during formation of new positions. If necessary, a user chosen co-ordinate can be specified instead of the default one.

Entity selection

In general, geometric entities are selected by using the cursor to point to a wanted entity and a mouse button to select it. When the entity is being selected, the cursor can point to any segment of the selected entity. In addition, an item can be selected by specifying its name or quoting its assigned entity database number.

Following any selection using the cursor, the first item of an allowed type found within the current cursor's hit-zone limits is highlighted and incorporated into the current rubber band display. However, if the item is selected for deletion or blanking, then this item is undrawn rather than highlighted. If an entity type has been specified, only entities of the specified type are searched for.

An optional acceptance procedure is available after a cursor selection. If none of the acceptance options is entered, it is assumed that the item has been accepted. The rejection of a selected entity results in the next entity of a permissible type that lies within the cursor's hit-zone being selected instead. Thus there is no need to position the cursor very accurately or to "zoom in" in order to secure a successful selection.

Note that during a wide range of operation, DIAMOND highlights the entity that lies under the cursor as it is moved above the drawing area. If the highlighted entity is the required one, it can be ‘grabbed’ instead of being selected and the selection accepted.

Non-geometric items are generally selected by their allotted name, but some short cuts are available. For example, a layer can be picked via items residing on it, a line-style by choosing an item that already uses it and a group by the selection of any one of its members.

Design versus drafting Design versus drafting Design versus drafting