Trimble Business Center

How of curiosity,  what difference is there between “drape object and elevate line”?
One thing I do know about drape object is. That object can not be used after it has been draped to a surface for any other commands.

If you have a linestring below/above a surface, and use "DrapeObjectsOnSurface" you will get the a draped line that follows the contours of the surface.

If you then "Explode" this draped line, it will become a polyline with the same horizontal properties as your original linestring, but with the elevations of the surface - and you can then play around with it.

I haven't used the "Elevate Lines" command, but from what I see, basically it will change the vertical properties of the linestring based on text labels, points, intersecting lines etc within a certain horizontal tolerance.

For example, if you select points and a offset tolerance of 1m, your linestring will gain the vertical properties of the selected points that are within 1m of your original linestring.

Drape Line is a Dependent Object - it takes its path from the source line and its elevation is derived from the surface. If the line changes path then the elevations update based on where the surface says the elevations should be. If the Surface changes then the line changes to reflect the surface. As lasse suggested the Drape Line can be changed to a normal linestring if you explode it, then you can manipulate it again independent of its source objects because the dependency has been broken. You can use a Drape Line in a surface model like any other element, just remember that while it is a drape line it is dependent on its source objects, so if they change it will change. You cannot however add a drape line to the surface that it is referenced to (that creates a circular reference which is illegal like any other application, but you can add it to other surfaces no problem.

The Change Elevation command has a elevate by Surface function that will derive the elevations for a line from the surface and add VPIs along the line where it crosses a triangle side. You can also apply a vertical offset to the line from the surface if you want the line to be Surface Elevation +/- a value. The elevations in this case while derived from the surface are not a dependency - so the end result is like a Draped Line after it has been exploded.

The Elevate Lines command has a number of ways to elevate a line from 2D to 3D. Again this creates a 3D line with no dependency on other data. You can elevate the lines using 3D Points, 3D Lines that cross the 2D line (e.g. elevate a line from contours), Text etc .

So the key differences are the dependency of the objects being present or not.

Alan

So to say there is not any negative reason on using change elevation by surface.  I kept wondering if there was a big impact on using the drape over change elevation.  I have used drape and was not pleased the way it locks the line work from being used.  So I started using change elevation.  just a small question with a big answer.  I was not aware you could explode the drape object.