Validate as DTM

You use this function to validate a DTM.

Caution: Do not set a DTM to validated=true by editing the DTM file in a text editor. If the DTM file is manually edited in this way, it does not correct any validation errors that may exist, and so any subsequent processing with the DTM may produce incorrect results or errors.

To run this function: Choose Surfaces > Validation >Validate as DTM, or...

• In the Function Chooser, type VALIDATE AS DTM, and press ENTER.

To validate the DTM, Surpac looks for several types of error shown in the following list.

• invalid edges - more than two triangles share an edge.

Note: If a DTM contains invalid edges, the error is reported and processing stops. To detect other problems, you need to correct the invalid edges and run VALIDATE AS DTM again.

• duplicate triangles - two identical triangles exist in the DTM
• intersecting triangles - two triangles intersect each other
• reversed triangles - these occur because the order and direction of the triangles makes it difficult for Surpac to interpret which side is the inside or the outside of the DTM

Note: This can create a Mobius geometry, meaning that functions that traverse the entire DTM might never find the end of the DTM.

• foldbacks - either a vertical triangle or a point where there is more than one Z value for the same X,Y location

Note: For DTMs created on a non-horizontal plane, the foldback test is performed as though the plane the DTM was created on is the active plane.

• holes - a space in the DTM that is not 'filled' by triangles
• disconnected trisolations - two distinct sets of triangles that share a trisolation number

You can generate a report for the errors encountered in your DTM. This can be written as a .not, .csv, or .pdf file. You can use the report to focus on the triangles with errors, by displaying only these triangles in Graphics. This can be useful when you have a large or complex DTM.

Tip: To help you view the highlighted problem triangles, type FACES OFF followed by EDGES OFF in the Function Chooser. This will erase all the triangles from the screen. Then to recall the triangles of interest back to the screen, type EDGES ON followed by FACES ON.

Fields on the Validate trisolation form

Field	Description
Layer name	The name of the active layer.
Report file	The name, file extension, and file path for the validation report. The file extension you choose determines the format of the report. If you do not want to generate a report, leave this field blank.
Object Range	The objects in the layer that you want to validate. To process all objects, leave this field blank.
Trisolation Range	The trisolations in the object that you want to validate. To process all trisolations, leave this field blank.
Colours for highlighting invalid triangles	The colour used to display each triangulation error in Graphics.

Ouput

Any triangles that contain the errors listed above are highlighted in Graphics , in the colour you define, and the trisolation is evaluated as invalid.

If no triangles are found to satisfy the points listed above then the trisolation is evaluated as valid.

You are advised by messages in the Message window of the following information for each trisolation:

• the object and trisolation numbers
• an indication of the status, that is, open or closed
• messages to say whether any invalid edges, duplicate triangles, and self-intersections have been found for that trisolation
• an indication of whether that trisolation is validated, that is, true or false

Note: The neighbours are removed for each trisolation that validated as false.

If you save the DTM after applying this function, the header record of each trisolation in the object will contain information to indicate:

• whether the neighbour network has been created
• the status (open or closed)
• whether the trisolation is correctly validated (true or false)

Note: This information is automatically removed whenever triangles are added to or deleted from a trisolation.

An example of the header record is:

TRISOLATION, 1,name=substope,neighbours=yes,validated=true,closed=yes

If you entered a name for the report file, it is created in the format specified and contains lists of trisolation and triangle numbers for triangles with errors, divided by error type.

Troubleshooting

Note: If you have defined a range of objects to be processed, or you are processing all the objects in the layer, and you have not input an Object 1 to the current layer, you may receive a warning that Object 1 does not contain any trisolations. This message can safely be ignored (Surpac will create Object 1 as a default object).

Message	Description
Corrupt triangle detected in input trisolation. 1st vertex: x = x1 y = y1 z = z1, 2nd vertex: x = x2 y = y2 z = z2, 3rd vertex: x = x3 y = y3 z = z3	This message informs you that a corrupt triangle has been found and gives the coordinates of the triangle vertices.
Cannot open Solids Modelling validation report file Cannot write to Solids Modelling validation report file	Check with your systems administrator to make sure you have file write privileges on your local network.