Command Help wireframe-surface-merge

 

Command Name	Menu	Quick Key	Link to Command Table
wireframe-surface-merge		udt	Click here

 

Description

Surface operation to update one wireframe DTM surface (or partial surface) with another.

This command does not require both surfaces or triangle selection groups to be cleanly/fully intersecting as surfaces will be adjusted to ensure an intersection before volume creation (there is a performance payload for this check/adjustment - if you are confident that both input surfaces are intersecting, you can use wireframe-surface-merge-intersecting instead, which will be more rapid for the same data inputs).

The Update DTM dialog is the user interface for this command.

How to use

Generate a new surface using the second wireframe data to update the surface elevation in preference to the first. The resultant surface area is the union of the first and the second wireframe surface data, so there is no restriction that the second surface be bounded by the first.

The operation of the command can be likened to using a cookie cutter at the boundary of the second surface to cut out the first surface, and inserting the second surface into the first.

Where there is a gap at the interface between the first and second surface, the gap is closed off with triangles, modelling the cut and fill relationship between the two surfaces. This is the key difference between this command and wireframe-surface-merge-intersecting.

Note: This command supports flexible wireframe selection.

Provided the second surface data is bounded by the first the cut and fill wireframe solids can be generated by projecting the two surfaces with the wireframe-surface-project command to an elevation beyond the range of the two surfaces, and then completing wireframe-difference and wireframe-intersection operations on these surface solids as follows:

• project the first surface down to the lower elevation (A)

• project the second surface down to the lower elevation (B)

• project the second surface up to the upper elevation (C)

• create the fill wireframe as the difference B minus A

• create the cut volume as the intersection of C and A

If the surface bounded by one or more closed strings is required, this can be found by the following sequence of operations:

• project the strings up and down to elevations beyond the range of the surface

• link the upper and lower strings into a single wireframe group

• intersecting the original surface with the string surface(s) using the wireframe-merge command

• delete the string wireframe surfaces, and the components of the original surface within or outside the strings as required.

If, instead of the complete result of the wireframe-surface-merge command, it was sufficient to replace the first surface with the second in the region of overlap then the wireframe-verify command could be used to generate the boundary string at the limit of the second surface, and then the previous command sequence could be used to do the cookie cutter operation on the first surface before adding the second. The surfaces are not guaranteed to be coincident on the boundary with this method.

	Related Topics
	Boolean operations wireframe-surface-merge-intersecting