Forums >> Revit Building >> Technical Support >> Importing / Modifying Topo from AutoCAD

jlevyarchitecture

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Joined: Wed, Dec 10, 2008
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Have a huge resort project where we have tried a number of ways to get the top into Revit 2012

- Island is 4 miles long, approx. 3/4 - 1 mile wide at wides point

- traced the image with both polylines and splines and set them to correct elevations in AutoCAD.

   REVIT can't handle importing the points in either file. (about 10 times the size as allowed)

- have brought it in with exploded topo lines and tried tracing the index contours (5 feet) and creating new surface with points in 

  REVIT but the perimiter of the island is extremely detailed and REVIT does it's "own interpreting" of the exterior shapes and does

  not follow the shape like we want when using points.

Any suggestions???   Really need help on this.

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WWHub

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Joined: Tue, May 16, 2006
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Topo lines and points are two different things.  Remember, topo lines are just an interpretation of what may be there based on some sort of point survey.  When hand drafted, two topos created by two different draftsmen using the same survey information could look very different.  So it is with Revit.  

That is why Revit's topo lines will never look like the ones done by someone in CAD.  However, the modeled surface will be correct for the points given to it.

For the most accurate model, original points information is always best.  If in finite areas you don't agree with the way Revit interpolates between the points given, you could add additional interior points to influence it but recognize that these are now just guesses.

For a model the size you are talking about, I suggest you break this up into smaller segments.  Perhaps using a "coarse" model for overall views, and separate, more detailed models for individual areas.  Just link in the appropriate models for the views you are working with.

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jlevyarchitecture

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OK,

I get that about looking different.  But what I don't get is why REVIT will not trace an accurate surface.  It does not want to create an accurate interior curve.  It always forces the contour to the outside.  Say you were tracing the island and you were creating a bay area or cove that dipped in. REVIT does not want to make a correct interpretation of the line. 

THe only way I can get this to work is if I go back and split the surface and delete the outside part.  I can only do that at elevation zero otherwise I cut holes in the surface at higher elevations.

I will look at cutting up the island and linking them, but when we start placing structures on it, it is going to get quite difficult.

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WWHub

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It will take you some time to understand the dynamics of revits topography.  As you place new points, Revit's topography lines continuously update to reflect the influence those poits give to the model. 

The only way to "trace" topograpy contours is to add enough points along what you are "tracing" but even then, you will probably not end up with Revit contours directly over what you are "tracing".  BUT!!!! The model will be accurate at each one of your points!

As far as your bay goes.... The elevation of the water at the edge and everywhere is theroretically the same elevation.  So you model the whole thing that way and split the topography and assign water to that flat portion.

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mbsteve

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Joined: Fri, Sep 22, 2006
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In Revit if you place topo points, and you only need relatively few of them, you can achieve very close to the topo that you are trying to do with ACad. The cove that you are working on get a soundings map, and take the topo points under the water surface, this will give you very accurate result. If you are working on a resort. You will want to know underwater resources and conditions of the Sea Bed anyway. You will probably need a pier of some sort, for what ever activities you plan boating perhaps guests, and certainly supplies will arrive by ship, you will need a respectable pier for such a purpose, and you will need to know where to put it, water depth and so on. You can fine tune your contour map, by adding points just below, and just above the contour interval, and then moving them around a little.

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