Create Cropped Surface from Dref?

[AllenJessup]

Can you create a cropped Surface from a Surface created by pasting Dreffed Surfaces.

I get an "Error creating cropped surface" message each time I try. The command line looks like this:

Command: CREATECROPSURFACE
Select first corner or [Object/Polygon]: O
Select objects: 1 found
Select objects:
Select point in the area to crop:
Point (616864.92,861180.44,0.00)

The Point is the point I picked inside the closed polyline I pick as an Object. The boundary of that area highlights showing it has accepted that as the cropping boundary. I have also tried tracing the polyline point by point. The command line then shows all the points I picked.

Working in 2014 SP-1.

Allen Jessup


Civil 3D 2012 SP 3 / IDSP 2014
Dell Precision T7400, Xeon CPU 3.16 GHz
Win 7 Pro, 64-bit,12 GB RAM, Nvidia Quadro FX 4600

[DaveM]

I believe I have seen an error in the past because the UCS was not set to world. You might varify that it is set to world before you try to crop.

[Neilw_05]

I've never been able to clip a surface made from pasted DREF's. I'm pretty sure it can't be done. Sorry for the bad news.

[AllenJessup]

I had read about that. But that's not the problem in my case.

I'm almost thinking I'll have to go back and crop each original surface individually then Dref and paste them together.

Allen

[AllenJessup]

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@Neilw wrote:
I'm pretty sure it can't be done.

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It would be nice if that were covered in help or the error told you it can't crop a Dref.

Allen

[DaveM]

Sorry Allen, I was not able to do it either. My previous suggestion was based on what I thought I had read on the forums.

[MikeEvansUK · Accepted solution]

You can create a "dummy surface" and paste the dreffed surface into it then crop from that one.

[Neilw_05]

As I mentioned earlier, I can't get that to work. Have you tried it Mike?

[Neilw_05]

I've concluded there are 3 parts to a learning curve:
1) What do the tools do
2) How can you apply them to meet varying scenarios
3) What are their deficiencies and limitations

Unfortunately parts 2 and 3 are learned largely through trial and error and a lot of time researching workarounds.

[AllenJessup]

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@Neilw wrote:
As I mentioned earlier, I can't get that to work. Have you tried it Mike?

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Mike is right. If you create a New Surface and paste the composite Surface that was created by pasting the Drefs in to. Then you can Crop the New Surface. This is the way it would work.
 

1. Dref Surfaces
2. Create the first new Surface
3. Past the Dreffed Surfaces into the first new Surface
4. Create the second new Surface
5. Paste the first new Surface into the second new Surface
6. Crop the second new Surface

That results in a new drawing with the cropped Surface.

Allen

[doni49]

I'm curious what is different about CROPPING a surface vs applying an OUTER BOUNDARY.

[Neilw_05]

An outer boundary only limits the extent of the triangles when you build the surface. All of the data is processed first, then the boundary applied.

A crop (clip) actually limits the data that is used to build the surface. It is a better way to manage a large dataset as it reduces processing.

[AllenJessup]

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@Neilw wrote:

It is a better way to manage a large dataset as it reduces processing.

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Exactly why I wanted to use it!

Allen

[MikeEvansUK]

Yes I tied it on a surface before I posted. First time I have used that command. Only just crossing over to 2014 in production env now we have a service pack.

Sorry it wasn't clear what you meant earlier. I use the dreffed pasted surface workaround all the time to edit the surface (trim back or expand etc) without effecting the original.

I figured it would work here as well.

[doni49]

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@Neilw wrote:

An outer boundary only limits the extent of the triangles when you build the surface. All of the data is processed first, then the boundary applied.

A crop (clip) actually limits the data that is used to build the surface. It is a better way to manage a large dataset as it reduces processing.

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Hmmm.  if that's the case, then I don't understand how it would be helpful to paste the surface in to a new surface and then crop the new one.

When you paste one surface into a new one, doesn't it read the WHOLE pasted surface?  Wouldn't the crop happen to the resulting surface?  It sounds like that would just make for twice as much data to process.

[MikeEvansUK]

I think you are missing the point. The whole surface definition is not taken through to the cropped surface. Only the extents of the crop are.

Creation of the cropped surface is on new or existing file and using workaround of pasted dreffed surface is only to assist in this creation from dreffed surface. Following cropping the pasted surface can be deleted.
Obviously you can just promote the surface, crop and undo the promotion to achieve the same result.

[Neilw_05]

I'm not sure about how the software handles DREF'd surfaces. All I know is I can't clip a DREF'd surface. If C3D can clip a DREF then it certainly has a useful purpose. As in Allen's case we have a very large coverage. If we want to utilize pieces of that large surface we could DREF it and clip it to where we need it.

I haven't tried Allens suggestion of pasting a paste into a new surface.

[doni49]

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@mikeevans wrote:
I think you are missing the point. The whole surface definition is not taken through to the cropped surface. Only the extents of the crop are.

Creation of the cropped surface is on new or existing file and using workaround of pasted dreffed surface is only to assist in this creation from dreffed surface. Following cropping the pasted surface can be deleted.
Obviously you can just promote the surface, crop and undo the promotion to achieve the same result.

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Ok thanks -- just trying to understand this.  I always thought that when you pasted a suface into another surface the ENTIRE source surface would be processed.  And I didn't think it would look at the cropping until after the paste. 

I like learning new stuff!  🙂 I can certainly see how something like this would be useful.

[AllenJessup]

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@doni49 wrote:

I always thought that when you pasted a suface into another surface the ENTIRE source surface would be processed.  And I didn't think it would look at the cropping until after the paste. 

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The entire Surface does come through to the Surface it's pasted into. The point of the operation is that you can't create a cropped Surface from the Surface you've pasted the original Dreffed Surfaces into. Once you've pasted the composite Surface into an new "dummy" Surface. You can create a cropped surface.

So to end up with a cropped Surface you first have to paste all the smaller Surfaces together. Then you need to paste that large Surface into the dummy surface. That creates another large Surface. Then you can crop that version of the large Surface to get a smaller Surface to work with.

Also the cropped surface doesn't end up in the drawing you're working in. You have to select or create another drawing to create the cropped surface in. The cropped surface behaves like a Snapshot.

Allen

[doni49]

Ahhhh.  That's the part I was missing.  When I DRef a surface, I usually leave it dynamically linked to the source.  It hadn't sunk in that you were promoting it -- in essence removing the dynamic link.

Having read your latest post, I went back and re-read some of your earlier posts in this thread.

Thanks for helping me understand and sorry for hijacking your thread.