In the Maptek Vulcan software, triangulation validity is an
important aspect of the three dimensional shape. The volume of a closed solid and the block
model reserves are both dependent on the triangulation being valid. Invalid triangulations may not return accurate
volume or reserve information.
Triangle validity in Maptek Vulcan consists of three tests:
Closure, Consistency and Self-Intersection.
Two of the tests are fairly self-explanatory. A closed triangulation is like a basketball,
it has no holes in it through which air might escape. A self-intersecting triangulation has triangle
facets that intersect one another.
Consistent triangulations are a little less intuitive.
Triangulations which pass the test for consistency have no triangle
side that is shared by more than two triangle facets. The closure test has a similar requirement
that each triangle side be shared by no less than two facets. Inconsistent triangulations usually happen
when two triangulations have been clipped (or booleaned) against one
another. The intersection has pinched
out and then opened up again. The side where everything intersects is now
shared by four triangle facets. Fortunately,
these inconsistencies are usually found at the edges of the triangulation and
are easily ‘cut’ out of the solid using the Model > Triangle Utility >
Cut tool.
To test a triangulation for validity you can use one of three
menu options: Model > Triangle Utility > Check, Model > Triangle Solid
> Check or Model > Triangle Edit > Check. Interestingly, the Model > Triangle
Surface sub-menu has no Check tool.
Depending on the context menu settings you may also right click on the triangulation
and select Check.
In the ‘Check Triangulation Validity’ panel you may select
which tests to perform and, subsequently, whether to save the boundary of the
failure. All three tests are selected by
default. When I save the boundary of the
error I always select to save to a layer.
The layer is easier to work with than an underlay even though you have
to remember to delete the layer later or have a lingering layer in your
database.
After clicking ‘Next’ the ‘Check Triangulation Stability’
panel is displayed. Stability tests are
not required to calculate an accurate volume or reserve. If you look at the test, the stability tests
intlude a tolerance value. Presumably,
you could set the tolerance to something so small that each of the tests (small
surface area, small angles and coincident points) would pass. Also included in this panel is the option to
select triangulations on the screen or by name. If by name is selected you will be prompted to
browse for the triangulations to test.
That’s it, by clicking ‘Finish’ you can test all the selected
triangulations for validity and stability.
Just a quick tip.
When I test a large number of triangulations for validity I always
de-select the stability tests. These
tests are not required for validity and this way I won’t get a long list of
failed stability tests, just any validity failures.
Hello, My name is Yanko González, I am a 10 years experienced Mining Engineer with knowledge in short, medium an long term mine planning.
ReplyDeleteI´d like to ask you, Have you ever try or check what really happens when we calculate reserves with triangulations are not validated? is there any measure about the accuracy I get with this "several hours of validating job" Sometimes We don´t have the time.
Thanks.
Yanko,
DeletePassing the triangulation validity tests ensures that the volume and reserves you get from that triangulation are correct. Sometimes an invalid triangulation will give the correct reserve results (sometimes it gives an error or a result of zero) but nobody (namely Maptek) will stand by those results unless the triangulation is modified to a valid state.
Thanks,
Tony
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