Volume Definition

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Volumes are defined when they are created. To create a valid volume, a minimum of two surfaces is required. One region is also required, but it is possible to use surface extents for this purpose in some cases. Not all surfaces need to be geometry objects; it is possible to define a constant surface. To create a finite volume, at least one surface must be a geometry object, or at least one region must be present.


SVOFFICE models are created using a series of surfaces stacked on top of each other to form layers. (Refer to the volumes topic for a visual representation of this.) The plan view surface area of the stack is defined by one or more regions that define the stack's planar extents. (Polygons can be converted to regions to achieve this purpose.) Regions cut through all layers by default but can be restricted in scope in SVOFFICE. (Note that region polygons ignore their elevation component, as it is not required.) Layers are formed by the volume bounded between adjacent surfaces, thus the total number of layers in the model will equal the number of surfaces, minus one.


Regions are added by selecting the desired object from the definition dialog. (If there are no region geometry objects in the project, this option will not be available.) Order is important, as later regions (i.e., those with a higher index) will dominate earlier regions (those with a lower index). Thus, overlapping regions are supported. Use the up/down arrows in the dialog to adjust the region ordering as required.


Surfaces are added by selecting the desired mesh or grid for each surface from the definition dialog. Surfaces can also be a constant value, defined by the constant field to the right of the combo box. Surfaces should not intersect each other, but in many cases they can pinch together and still form a valid volume. As with regions, the up/down arrows in the dialog can be used to properly order the surfaces in the list.


After pressing OK from the definition dialog, a volume is calculated and then displayed. (This may take some time for complex geometry, so be patient!) Each region-layer block will receive a unique color, so it is possible to get a good "feel" for the 3D volume being created. Individual region-layer block pairings can be enabled or disabled via the Geometry Properties window to aid in visualizing the interior of the volume. To change the geometry, open the definition dialog again and modify the inputs as desired; this will generate an updated view.


If a preview does not appear, it is possible that there was a problem with the specified inputs. Example problems include:


Region polygon(s) are outside the range of every surface
Surface order is incorrect (for example, Surface 2 is below Surface 1, which is backwards)
Insufficient data was supplied (for example, only one surface was provided)


Upon editing or creating the volume, the "check for surface pinchouts" action will be performed automatically. If problems are found, a warning message may be displayed (see the help topic for the action for more information).