Category Archives: Mesh

3d Lines & Drafting

Our BIM Manual has a description of what we model, when we model elements, and why we model them. The third element, the “why”, is one of the most important parts of managing a high quality model, and producing accurate and well coordinated documents from that model.

With this in mind, a lot of our project teams have been pushing the boundaries of even the most basic drafting elements. One example of this is in site models & plans, specifically property lines and setbacks. Intuitively, it makes sense to use polylines or even fills for this. Thinking outside the box however, it makes more sense to use a 3d element, such as a grid or a morph.



Using a 3d solution allows you to coordinate the property & setback lines on all (or select) stories simultaneously with fewer elements. It also allows coordination of the building in 3d. Since our final CD Site Plans are typically drafted anyway, this is largely a process and 3d solution. But using a morph does allow for boundary line type & pen control, so it can also be incorporated into the final documents.

Simplifying Site Mesh

Some site surveys we get are very detailed, showing contours every foot even for very steep sections of the site. Some of these sites also have a high number of nodes associated with the original DWG file from the surveyor. In the image below, the bold gray line towards the bottom of the survey is actually the same line type/pen as the rest of the contours, but it is selected and all nodes show as gray. The nodes are so close that the line appears as a bold gray line.

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The result of this highly detailed site survey is a very high polygon count for the site model. An easy way to simplify this is to do a little editing before applying the contours. In illustrator you can open the original DWG and select simplify. If “Straight Lines” and “Show Original” are checked you will get a preview of the reduction in nodes/segments that will result from the operation. Adjust the Angle Threshold until you get a simpler but still accurate site survey.

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Next export the drawing from Illustrator back to DWG and place into the ArchiCAD worksheet as normal. A little additional drafting may be required (as is normal for any survey) to consolidate linework & make all polylines continuous. The result is a much simpler topo drawing that can be used for creating site models and for drafting 2d site plan elements.

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Notice the above image has much simpler contour lines. This image also excludes all property & setback lines. These should always be pulled from the original survey and reapplied to the revised topography to ensure all surveyed property line elements are at the original precision.