What's a block
The term block was introduced by Autodesk (AutoCAD) more than 30 years ago. CAD software such as AutoCAD and gCADPlus use blocks in order to increase drawing efficiency. The figure below shows a typical symbol for a plant. The symbol at left is composed of several elements such as polylines, but these have been combined into a single named entity. The symbol on the right looks identical, but is is made up of individual entities.
A landscape plan made by copying the block to create the plan is much smaller in file size and will zoom and pan more quickly than one made by copying symbols such as the one on the left. If as is commonly needed you need to move a symbol. it is much easier to select a block rather than pick all the entities that make up a symbol such as the one on the right. That is especially the case when symbols overlap.
Block can be used for shapes other than planting symbols.
Blocks are not just used for planting symbols, any group of entities can be a block. The figure below shows some examples.
The importance of block Insertion points
When a block is inserted into a drawing it is anchored at its base point. the anchor point of a block is defined at the time the block is created.
Tip: try and define convenient base points when making a block.
Make blocks inside and outside drawings
A block can be made 'inside' a drawing by selecting a group of entities, right clicking and selecting make block.
Selecting that command throws up a dialog box that enables selection of base point and the ability to add a description.
Making new blocks outside a design
A block made inside a drawing is not available for use in other designs. For a block to be used in many designs, start a new drawing and build the design. Save the drawing in an appropriate location and use the BLOCKS command to browse to it when required.
Tip: Make coordinate 0,0 a convenient part of the design for a block. That point becomes the base (or anchor) point for the block.
The figure below shows a design for a block for an existing tree on site that needs to be removed. When inserted into a drawing, the block name is the same as the file name.
Nested blocks and circular references
It is possible to create blocks within blocks. These are often known as nested blocks. The figure below shows importation of a block containing other blocks into a gCADPlus drawing. This can be a powerful tool as it is possible to pick out just the sub block you require from the nested set.
Close up view of the blocks inside imported block.
The use of nested references can be a very powerful tool in the gCADPlus environment.
Block names and AutoCAD
The inherent flexibility of gCAD+ can sometimes cause problems if there is a need to exchange files with AutoCAD users. GCAD+ allows the use of special characters such as brackets () and slash / in block names. However, these are not allowed in the AutoCAD environment and your exported DXF will not load in AutoCAD. The simple solution is to avoid the use of these characters in block names. We have also seen a similar problem where spaces have been left at the end of a layer name. Again, best to avoid leaving trailing spaces in layer names.