when creating or modifying a sub-region, why the geometry of the terrain surface changed?

[gagebao]

when creating or modifying a sub-region, will the geometry of the terrain surface change?

[barthbradley]

Because the color green is coming from the Topography's "Material" Instance Property.  

[handjonathan]

Hi @gagebao 

Thanks a lot for posting your question to the forums!   Has the solution suggested by @barthbradley helped with your issue?
 
We look forward to hearing back from you with more information so we can help you as a community! 

[gagebao]

Thanks for your reply!What I want to ask is that I created a sub-region on the Topography as shown in the first picture, Then the Topography's elevation value changed as shown in the second picture, And the contour lines also changed. Will the creatiin of the sub-region change the original Topography ?

[barthbradley]

What you are describing and showing is not the result of creating a Subregion. A Subregion CANNOT impact the existing elevations of its Toposurface host. Something else is going on; I'm certain of it.  

Post your Revit Project File here.  

Help | Create a Toposurface Subregion | Autodesk

[gagebao]

I discovered the change in contour lines when I created a Subregion in the Topography. It’s just a simple model. You can try to create a Revit model like the one in my picture. When you drag the Subregion to move, you can also find the change in contour lines.

[barthbradley]

Is this what you are describing?  If so, what are you doing exactly? I don't understand your workflow. 

[barthbradley]

You know that you can edit/add/delete contours via Site Settings; don't you?