Mesh Editing Tips

by GRAPHISOFT and lnagy · updated: 12.10.2003
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The following contain some useful tips about working with Mesh objects in ArchiCAD.

  1. When you click on a node of the Mesh polygon or one of its ridges on the Floor Plan, you can see its height value. As default, this is shown relative to the Basis Plane of the Mesh. When this option is used the height value of the node/ridge displayed here and its value displayed in the 3D Window may differ. For example, there is a Mesh placed with a base level of 2,0 meters above Project zero height, and there is a ridge in it 2,5 meters above the base level. If the height of the ridge is viewed on the Floor Plan, it will be seen as being 2,5 meters. In the 3D Window, however, its absolution height is shown, which in this case equals 4,5 meters. So a user might need to count a lot because different values need to be entered depending on whether the Mesh is edited on the Floor Plan or in the 3D Window. One simply solution to this is to switch the Mesh Point Height to be relative to the Project Zero height.
    Mesh-1.png
    This way the values displayed in the Floor Plan and the 3D Window will always be the same. Unfortunately, this setting is currently not preserved in ArchiCAD so you need to switch to Project Zero with each new edited Mesh Point.
    There is another solution to this problem. It is to always set the height of the Basis Plane to 0,00 meters; the height of the Project Zero. This way the height of any Mesh Point will be the same relative to the Basis Plane and to the Project Zero. In this case the height of the skirt of the Mesh should be set to a high enough value so it will extend lower than the lowest Mesh Point below zero. For example, if the lowest Mesh Point’s height value is -4,50 meters, then you should set the skirt height to 5,0 meters or so, so there will be some body of the Mesh even at its lowest height points.
  2. It is a fast an effective way of creating terrains with the Mesh tool is to obtain a drawing from the surveyor with elevation lines shown on it. Using these elevation lines, one can draw the outline of the terrain with the Mesh tool. Then, one can SPACE-clicks each elevation line to create ridges in the terrain. Set the value in Tools\Magic wand Settings… to an appropriate value, so the resolution of the ridge lines will be what you need. Use the ‘No Surface Fitting’ item from the drop-down list in the appearing Dialog, as you will later set the height value of all Mesh Points. When you are finished creating the ridges, click on each one and set its height value. Make sure to check the ‘Apply to All’ checkbox, so all Mesh Points on that ridge will be changed to the entered height. After this, enter values for the remaining Mesh Points along the outline polygon of the Mesh.
  3. When using the above method in 2., very large Mesh objects might become created with hundreds or even thousands of Mesh Points. In such a case, there can be a technical peculiarity. ArchiCAD gets the data of the Mesh Points and tries to triangulate the surface from this. When Meshes contain lots of Mesh Points, the distribution of Mesh Points along a ridge can be such that it becomes mathematically impossible for the program to create certain surface triangles. In such a case, ArchiCAD will not be able to generate the 3D of the Mesh. The warning sign of this is when certain ridge lines of the Mesh disappear from the Floor Plan. As soon as you see this, you know that the triangulation of the surface was not successful along that ridge of the Mesh. In such a case you can select the Mesh, and cut it into smaller pieces (e.g. in half or in quarters). This way the number of Mesh Points in one Mesh will be decreased and there will be significantly higher chance of the program being able to find a way to correctly triangulate the surface of the Mesh.
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