The creation of Mesh elements is quite important in any ArchiCAD model.

The basic steps are relatively straight forward – simply requiring the repetition of certain functions at various stages in the overall sequence.
The steps required to draw and edit a mesh are listed below:

1. Draw the Mesh outline, using the mesh tool – it will look like a simple slab to start with
2. Draw the individual Contour lines using Splines, or use imported existing DWG information
3. Highlight/select the Mesh on Floorplan you have just drawn
4. Select the Mesh Tool
5. Hold down the Space Bar (Magic Wand) and click on a contour LINE
6. Choose the option to add 'Fit to User Ridges' (this will imprint the single contour onto the selected mesh)
7. Repeat Steps 5&6 for all contours – the mesh will still be flat but will have the contours imprinted
8. You can now delete the original splines, or preferably put them onto a hidden layer (in case you need them again)
9. Highlight/select the Mesh on Floorplan – you should see all the hotspots on all the contours lines
10. Click on a hotspot on a contour – a pet palette will appear, choose the 'Elevate Mesh Point' option
11. On the subsequent panel, enter the value for the height of that contour - ensure the option to 'Apply to All' is selected, this will apply the height to all points on that contour

12. Repeat 8-10 for all contour lines
13. View the mesh in 3D
14. Select the mesh in 3D
15. Click on a mesh point that is not at the right height
16. The Pet Palette will appear, choose the last option and edit the height of that particular point

Also in the ArchiCAD Help, more inofermation on Meshes can be found in : Contents > Virtual Building > Construction Elements > Meshes