giovedì 3 agosto 2017

BIM for landscape?


Can the BIM be used for modelling landscape? Before summer holidays I share a research that we made. Thanks to Laura Ferrara and Maria Rita Longo for the support.


Many landscape architects believe that BIM is strongly bound to the building model as the word sais. In some ways the switch to BIM is a bit difficult because it requires a substantial change in the processes, but at the same time BIM don’t creates only a 3D model, it gives to all the component the info you need. In this way you don’t need to create every single detail of the landscape component but you just give them all the information every landscape architect needs to know about. For example you don’t need to draw the tree in every single detail because you can have the info about that tree: which kind it is, how many water does it need; in this way you work with a lighter model. This is also very important during the executive phase because it concern you to avoid every kind of interference because everything is simplified. Thanks to BIM process, also for landscape, we can earn time and money because we can know problems and quantities in advantage.

We are going to talk about the use of Revit instrument. Through this software, the designer exploits the BIM capabilities. For landscape there is no specific system family so, in this way, we have to study different way to work with.






1.Topography 

If the landscape already exists the best way to start is the topography. This can be created by an imported instance, from points file or created by placing points. Another way is to create the topography from model lines drawn at their respective elevations with the help of different reference plans to which the lines are hosted. 

In this way we can have a good control of the topography but at the same time we can have some problems with interpolation issues. 



  • The Topography does not follow the contour lines accurately. This is because Revit does not see the contour line; it only sees the points along the line. It takes all of these points and interpolates the grade between them. So regardless of how many points we have along a contour line, there will almost always be areas where Revit triangulates these points inaccurately. 
  • The Topography can’t be modelled on the top of the building roof without filling it in the entire structure



How can we resolve these problems?



For the first problem the solution is not adding more points along the line, sometimes this will make it more difficult. First you have to identify the elevation of the area that doesn’t follow the contour you need, then you have to add one or two points with a bigger elevation, to the topography, in this area and not to the contour. 


In the second case there is no solution with the single use of the topography tool because there is no way to define the bottom extents of Topography. So while Pads can be used to push Topography down, there is nothing that will push it up or create a void in the middle of it. So how do you model the Topography on top of the structure? There are different way:






















One of the most common used workarounds is using Floors or Roofs. They work quite well if you have a consistent thickness and if it’s combined with an In-Place Void, the Floor can have a varying thickness.
  • We can copy the topography in another revit file, cut the topography with the building pad and linking this one in the model. 
  • Another solution concern the use of AutoCAD. We can cut the topography, then open it with AutoCAD and extrude it down; then put it back in Revit family mass and insert it into the project.
  • We can create a series of horizontal reference planes, or Levels, then from Massing and Site we choose the In Place Mass tool and we can create a mass element. Remaining in the In Place Mass and using the Reference Planes we can draw splines following the contours of the isolines. Creating curves hosted at every level we can select them two at time and Create Form Solid, then we can do the same with the others.

To each level is hosted a line created in the In Place Mass tool
















































2.The ground 


The ground can have different kind of surface such as concrete, asphalt, pavers, curbs, etc. It can be done by: 
  • Subregions
  • Pads
  • Floors 
The subregions work well for quick areas draped over Topography and are fine for large-scale visualization. But subregions do not work well once you move into finer detail graphics and documentation because they cannot have hatch patterns and they don’t have edges. In the end they also don’t have curves, complex shapes, enclosing shapes and overlap. 
The pads require a Topography host, since their main purpose is to push Topography up or down to a specific level. This is a particularly nice feature in section, as there are no gaps between the Topography and Pad. Unfortunately, Pads can only slope in one direction, using the slope arrow. 
The floors can exist without the topography but at the same time they can’t put the topography up or down; they have editable types and structures. They can be given a simple slope with a slope arrow, but they also have another feature that makes them infinitely more flexible: Modify Sub Elements, without a slope arrow. 


References:
http://worldlandscapearchitect.com
https://landarchbim.com

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