This 49 minute lesson offers an explanation and demonstration of creating a site model using the mesh (terrain), slab (hardscape) and object (trees etc.) tools. A prepared survey file is brought in as a DWG and placed as a reference underneath the building to use as base for tracing the site boundaries and recreating the topographic contour lines.
Two versions of the DWG are available here on this page for following along with the video, one in imperial (feet) and the other in metric. An independent Worksheet is created for placing the DWG into the file; in versions of ArchiCAD that do not have worksheets, an independent Detail window may be used, or in version 10, an extra “dummy” story may be created so that the “ghost story” option provides a tracing image similar to Virtual Trace.
Ideally, the scale of the Worksheet (etc.) should be set to the intended printing scale (e.g. 1/8″ = 1′-0″ or 1″=20′-0″ or 1:100 etc.) of the site plan before importing the DWG so that the text appears correctly in relation to the site geometry. The File menu > External Content > Place External Drawing command is used to import the DWG. (In the Start Edition one may use the File menu > File Special > Merge command instead; the effect is different, but for this lesson it will work just fine.)
While placing the DWG, the Drawing Unit dialog offers the opportunity to confirm the size of the internal DWG measurement unit, which will generally be Feet in the U.S. and may be Meters or Millimeters in international usage.
After importing the survey, it is important to verify that a known distance from the drawing matches the distance displayed by the Measure Tool. If it does not, then the simplest way to correct this is to calculate the proportion difference (e.g. the size is 12 times or 10 times too big or too small, etc.) then Undo, and reimport using a different measurement unit. Repeat if necessary until the survey dimensions are verified as accurate.
On the ground floor, a new View is created with the Site layer combination. (Note that the Quick Options palette makes it easy to change layer combinations on the fly.) If necessary (as demonstrated in the international project file) it may be useful to adjust the Site layer combination to include the exterior walls of the building; remember to Update the layer combination after making the change so it is recorded properly.
The survey worksheet is set up as a Trace Reference, then with the Drag Reference command (using the button in the second row, second from the left, in the Trace and Reference palette) the survey image is repositioned to coordinate properly with the building.
The relationship of the current Project Zero – often this is set as the top of the finish floor of the main story – to Sea Level or a standard height datum – is set in the Options menu > Project Preferences > Levels and Project North (or a similar command; this varies in different versions of ArchiCAD). The Sea Level or Reference Level is set to the appropriate offset from the Project Zero so that when the terrain is created it is easy to input and reference grading elevations based on the external datum value.
The Mesh Settings elevation is then set up to reference the Sea Level or Height Datum rather than the Current Story or Project Zero. An initial base is created by tracing the outline of the site boundary, snapping carefully to each node point. After the mesh is in place, it is viewed in 3D – it is a flat slab, floating a bit below the building.
To edit the details of the mesh height values, it is important that the mesh tool be active in the Toolbox, and the mesh be selected. Each node point is clicked on, and using the pet palette Z-height option, set to the appropriate height above Sea Level or the Height Datum. Do not click the Apply to All checkbox when changing the Z-height; do each one of these nodes one by one. The mesh is viewed in 3D again, and now the prevailing grade is clearly visible, and the building is partially enveloped by the terrain.
Before creating each topographic contour, add new node points where that contour line meets the site boundary, then set the height of each node properly. This sets the exterior of the mesh to a more precise representation of the grade.
To create a contour line, click slightly inside the mesh perimeter, then click a series of points to roughly trace the topographic line. Click twice on the last point to finish, and accept the default choice (“match to existing contours) in the Add Points confirmation dialog box. After creating the contour line, with the mesh still selected, press down on any of the interior points of that polyline, and use the Z-height option in the pet palette to set the height of all of the points in that polyline (click the checkbox “Apply to All”).
Repeat the process for additional contour lines as needed, and know that you can add more at any time. Do not overdo it, and don’t put too many node points while tracing – this will add needless polygons (detail) to your model that may slow down the responsiveness as you view and work in 3D.
The mesh element may be set to display all contour lines on the plan, which can get messy as more contours are drawn and ArchiCAD calculates all the triangular surfaces necessary to represent the geometry. To turn this off, use the option in the Floor Plan and Section panel or popup > Outlines to Show User Defined Ridges rather than Show All Ridges. A similar option exists for the 3D model representation, which you may adjust in the Info Box or the Mesh Settings: choose All Ridges Smooth in the Model panel.
When viewing the Sections of the building, use the Design menu > [Connect submenu – in ArchiCAD 15] > Solid Element Operations (SEO) command to carve out the floors from the terrain mesh. Select the floor slab and make it the Operator, select the terrain mesh as the Target, and use the Subtraction with Upward Extrusion command – voilà – the terrain is cut to make way for the floor and walls above.
To add hardscape such as a patio, use the slab tool and set the elevation properly, perhaps by eye-dropping an actual floor slab. If it is buried in the terrain, use the SEO palette to carve out the slab from the terrain. This may be done from the plan view, since it is easy to select each of the elements.
The slab hardscape may be set to a different material, perhaps a concrete or stonework. If you’d like to see a hatch pattern on the plan, you may activate the Floor Plan and Section > Cover Fill option, and either use the Fill that is associated with the material, or set it to an independently selected Fill.
Finally, the object tool is opened and tree objects are located using the Find by Keyword option. To place the trees at the right elevations in relation to the terrain, the Gravity option is turned on, and the sub-option selected to Gravitate to Mesh (rather than Slab, Roof or Shell). Then when the tree object is placed, either on plan or in 3D, it will pick up the height of the underlying mesh and use that as the base height for placement.
NOTES FOR USERS OUTSIDE THE USA
You may need to right-click the following links and select Save Link As to download the file to your computer. Remember to unzip the file before trying to place the DWG into your ArchiCAD project.
You may need to right-click the following links and select Save Link As to download the file to your computer
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