Surface boundaries and boundary types

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You'll almost always want to add an outer boundary to your surfaces.

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Outer boundaries define the outer extents of the surface.

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In prospector select the existing ground surface from the services collection

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right? Click on it

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and select rebuild automatic.

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This is a toggle option and when it's on the surface

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will update automatically when any changes are detected to its definition,

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expand the surface definition prospector,

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right? Click on boundaries and choose add

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set the name to alter,

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make sure the type is set to outer.

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We'll explore other options later,

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a boundary can either be destructive or non destructive.

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A destructive boundary will destroy or delete

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any triangle side that is outside the boundary or is crossed by the boundary.

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The result is that only whole triangles inside the boundary are preserved.

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A non destructive boundary will trim any crossing triangles to the boundary line

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and delete any whole triangles outside the boundary.

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In this example, we are using a non destructive boundary

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and the mid ordinate distance is set to 10 ft.

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When I apply this boundary,

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the surface edge is now tessellated,

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clearly triangle sides cannot be curved.

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So there'll always be straight edges on your surface boundary.

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The tessellation is controlled by the mid ordinate distance.

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If the mid ordinate distance is small,

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then additional triangles will be created to ensure the setting is honored

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for our boundary select non destructive brake line

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and leave the mid ordinate distance set to 1 ft

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click. OK. And in the drawing, pick the white poly line as shown for the boundary,

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the polyline remains linked to the surface.

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If you delete it,

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then you're deleting the surface boundary and the

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surface will revert back to its original size.

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Use grips to edit the boundary.

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When you change the polyline,

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the surface rebuilds automatically and resizes to the bounding entity

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in this area. Here we have a polyline that represents a building outline.

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We don't want to display contours inside our building.

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In prospector under the existing ground,

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there's an item labeled masks,

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masks are not boundaries,

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they can be likened to a wipe out in a

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cat.

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Unlike a boundary

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triangles inside a mask are not deleted from the surface.

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They're just not displayed,

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right? Click on masks and select crate mask,

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select the building poly line in the drawing and press enter

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in the crate mass dialogue, set the mask type to inside and then click OK.

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Contours inside the mask are now hidden

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but the surface is still there inside the building.

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And if I were to perform a volume calculation,

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it would still include triangles inside the mask.

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Now let's create some boundaries for this lake and island

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in Prospector, right? Click on boundaries and choose. Add

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name this boundary. Lake

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set the type to hide.

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We don't want contours inside the lake.

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Make sure that nondestructive brake line is selected,

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accept the default mid ordinate distance and click. Ok.

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Pick the outer lake polyline

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and the surface is now trimmed to our lake.

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Add another boundary and name it island.

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This time set the type to show

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again, it will be non destructive and the mid ordinate distance is 1 ft

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click. OK. And pick the island polyline.

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The surface is regenerated inside the island.

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You can nest,

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hide and show boundaries

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as many times as you want.

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If I review the surface in the object viewer,

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you can see the surface still exists inside the

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mask but has been deleted inside the lake.

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Delete the lake and island poly lines in the drawing and the surface will rebuild.