As a base for their design work, landscape designers commonly work with architectural drawings. These drawings can take many forms - AutoCAD dwg files, DXF files from a variety of other CAD software and scanned drawings of hand drawn or computer plotted prints. This paper provides some advice on how to handle those in the gCADPlus environment.
We will begin with a check list of recommended steps to take when handling dwg files from an architect. The latter parts of this page describe a case study.
Not all designers working with AutoCAD work in an organized way. It is not uncommon to be sent a very 'messy' dwg file complete with unwanted blocks, missing linetype, fonts, orphan entities, badly named layers and so on.
1. Download a copy of Teigha File Convert from http://www.opendesign.com/guestfiles/teighafileconverter, install it and convert your dwg file to a DXF file. DXF is a very clean CAD drawing standard and the drawing will be cleaned up in the conversion process. The figure below shows an example.
Note that we are converting to DXF version compatible with Release 14 of AutoCAD. that version of AutoCAD was far and away the most stable version. Any extraneous information stored in late dwg file formats will be stripped away.
2. Start gCADPlus
Via tools>Plugins, set the Import characteristics as shown in the figure below.
This is an important step because many AutoCAD users make very messy hatch patterns.
3. Choose File>New an start the new drawing with the your default template, make a new layer (A-ARCHBASE might be a good name), make it current and import the DXF file onto that layer. You have of course made a default temple with all your favourite layers, linetypes, hatch patterns etc.
4. Select all and force all entities to the layer L-ARCHBASE
Save the drawing in its efficient native cd format.
Here is some data you might find interesting;
Original dwg file size - 1.48Mb
DXF file - 8.1 Mb
Resultant gCADPlus lcd file - 0.176 Mb - a huge decrease in file size with a resultant improvement in zoom, editing etc.
If perchance the architects makes changes to the dwg file, delete everything on layer L-ARCHBASE and inport a new DXF file.
Working with AutoCAD files
The ideal situation for a designer is one where the architect (or survey firm) has produced a plan of his building(s) on the site and used AutoCAD software to do that. Because gCADPlus is command compatible with AutoCAD and allows insertion of AutoCAD's dwg files into a new drawing, life can often be very easy. Many entities required for the development of a landscape plan (the base plan) are already present. They will be drawn in model space at full size. [Do be careful, we have had drawings where the information we want has been placed in layout space and not full size]
The figure below shows the Insert option on the File menu being used for that purpose.
This approach is fine if it is certain that there will be no changes to the architects plan. The reason being that by using the insert command, you are breaking the architects plan up into its constituent parts. The figure below shows the result of the use of the insert option with one entity selected. Clearly, the base drawing has been broken up (exploded) to its parts.
If a change needs to be made to the architectural base drawing, then each entity will have to be removed. That can be a tedious operation.
A better approach is to use the blocks command and attach the external drawing as a block to the current drawing. The figure below shows that a single click on the base plan shows that the whole base plan is a single (block) entity.
This approach has its advantages in that if the architect makes changes to their plan, the block can be removed easily and a new version inserted in its place. There are some disadvantages though. In common with most CAD software, it is not possible to snap to points inside a block without exploding the block. The figure below shows us trying to place a rectangle using osnap to an intersection. In its present form, the software does not allow this. You can work around this limitation by keeping the inserted entities on one layer - exploding the block on that layer and make sure that all entities in the imported block are kept there.
Our present approach is a hybrid of the two systems set out above. We first open the drawing in gCADPlus, save it as a gCADPlus drawing, then move all entities to a layer we call L-BASEPLAN. We make the color of that layer one that is easily seen (magenta). Then we use the insert command as discussed earlier. Entity snap now works and if there is a change to the architect's drawing, we can simply remove every entity of the layer L-BASEPLAN and try again. The figure below shows the result.
Osnap now works. There is an added benefit. In this instance the gCADPlus (lcd) file was only 50% the size of the corresponding AutoCAD (dwg) file. General drawing operations are thus speeded up.
Working from scanned drawings.
While not as convenient, it is possible to work with a scanned copy of an architects drawing. The figure below shows an example of what you might receive from an architect.
We suggest that you use the Draw>Insert Raster tool and insert a copy of this scanned image into the gCADPlus environment. It is useful to insert the image at a scale of 1.0 (taking the scale image at insertion option off) because if the original scanning has been done carefully, there may not be much need to re-scale the image to match the dimensions of the 'real world'.
Note that not only can the option to scale the image on entry be turned off, it is also possible to change the resolution of the scanned image at insertion. A resolution of 150 dpi rather than the 300 dpi shown below should be ample to allow accurate copying. The figure below shows the setting we used to insert the scanned image of the drawing above.
Once the scanned image has been placed, we find it convenient to turn off the Properties box so as to have more screen real estate. It is also a good idea to select the image and use the tools drop down to make sure that the image is at the back. Any new lines we draw in the copy process will show clearly (and can be easily selected for editing. In addition, we like to move the image file onto its own layer so it can be turned off later (rather than deleting it).
Finally, the drawing color is to red (use the color toolbar item to do that) and begin to trace over the 'substance' of the drawing.
We continue to trace over the important features of the base plan. In the figure below, we have adjusted the thickness of the line to make it more obvious. Because we are copying (tracing) there is a danger that entities may not quite reflect the true circumstances. For example, the boundary line is not quite vertical (as it should be). We will edit the angle of the line at a later stage to make sure that it is vertical (and that the house walls are also square).
The architectural drawing showed the position of some existing trees. While it was not necessary, we made a new symbol to match the scanned tree symbol. One copy has been placed at the side of the scanned drawing for ease of viewing.
The image below shows the final result (still with the image showing).
Now that the image no longer displayed (layer off), we square up entities using the properties box. In this drawing, most entities should have an angle of 0, 90, 180, 270 degrees. With sufficient skill and foresight, it may have been possible to use Polar settings to archive that during the copy process.
Next we check scaling. The front boundary is 13 meters (13000 mm) wide. it reads 13398.52 so the CAD drawing needs to be scaled by 13000/13398.52 = 0.9702. The figure below shows that we now have an accurate model to work with. How much easier would it have been if the architect could have been persuaded to part with a CAD version of his drawing.
Now it is a simple matter to work on our design. Because the model is full size, the symbols from our library can be placed properly. We decided to emphasize the 45 degree roof angle by reflecting it into the front garden (and use bands of 45 degree planting) to create a secluded sitting area.
And part of the (unfinished) design in layout space.
and the rear garden design. The 45 degree angle is further emphasized. Click on the image to see a PDF version of the drawing. No text or plant schedule has yet been applied.
Tip: DXF files from other CAD software can be used in much the same way as DWG files.