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Clip Surface Command

Benson Shaw


The 2d clipped surface command creates a special and edit challenged object. For a clipped surface consisting of a closed outer boundary polygon or poly line "pierced" by one or more polyline or polygon holes:

1. Split by point tool does not effect interior shapes.

2. Split by line tool does not split interior shapes unless it also splits boundary at two or more places.

3. Clipped surface cannot be returned to the boundary poly with one or more interior polys. (a double click enters a group, an extrude, a solid addition, etc to reveal the original objects).

4. Selection of clipped surface does not reveal vertex count of interior shapes - only the boundary object is counted, although 2d Reshape tool does reveal the verticies.

5. Clicking through the verticies in the OIP never "enters" the interior shapes.

6. Removal of interior polys is not intuitive. Here is one way. Anybody know other ways?:

Select clipped surface with 2d reshape>option select (drag the lasso) the interior shape>move the shape outside the boundary>clip tool (remove inside mode) to delete the shape. Only the boundary and other interior shapes remain.

7. Convert to polygon command of the clipped surface creates a group of polygons with enough vertical edges to "split" each interior poly (why always vertical?)

8. Sometimes additional clips to a heavily clipped surface result in a change to some of the earlier clips.

I wish for an update to this command. Allow me to enter and edit the original set of objects from which the clipped surface was created.

Why do I care? To make a 3d extrude with holes (a steel plate with letters or other holes cut through it), one needs a clipped surface to extrude, (or a bunch of extrudes to create a solid subtraction- also tedious). If the rendered extrude reveals a need to remove some of the holes the process is non intuitive. If there are many holes, it is tedious to reclip all the holes from a copy of original polys (if available), esp because the clip tool clips only a few polys each command.


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That does work, and thanks for mentioning it. I hope there are more ways.

But the decompose command breaks the polys into their component segments. So then I have to select and recompose. If the internal polys are close together, the lasso select is required to recompose a single entity. If the clip command caused a bunch of stacked points in the internal polys, then the recompose may not work.

That's another bad thing about the clip surface command - complicated polys sometimes clip with increased point count, including stacked points. That can mess up an extrude and cause looooong renders. I did one recently which created 12 stacked points where only one corner point existed prior to the clip surface.

OK, keep em' comin.


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So then I have to select and recompose.


Not when I've tried it. You recompose IMMEDIATELY after decomposing. Everything that is decomposed is already still selected, you don't have to re-select anything as far as I can see. It's a quick step. Then you delete your polys after recomposing.

Doesn't solve your other issue though. One thing I've often wished for is the ability of VW to do operations on groups - your cutting objects would be in a group, and you would use the group to cut.The you can edit the group. Other applications have this ability, and it would be useful in lots of situations. How many imes have I been caught out trying to o something that VW tells me I can't do, then to realize that it is because one of the operands is a group?

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Try using a scratch sheet set to Lo-res for Clipping and trim procedures.

Thanks, islandmon & David. Most of my files have a "Sketch" design layer to test operations on copies of objects. And there is usually a separate test file on my desktop. I will set that one to 2d and 3d low rez in Prefs. Of course, I don't always start there when I should. Anyway, I will try both the Decompose/Recompose Cha Cha and the Lo Rez Hi Rez Two Step in my next VW Clip Surface Dance.


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Why do I care? To make a 3d extrude with holes (a steel plate with letters or other holes cut through it), one needs a clipped surface to extrude, (or a bunch of extrudes to create a solid subtraction- also tedious).

Tedious, huh? Tell me about it - I think I have something like 10 levels in some of my solids!

However, while I think I understand what you are after, I'm not quite sure if the tediousness should be extended to 2D-polylines. A Boolean chain (that's the tedious part) should be introduced and all of us doing simple 2D drafting would be seriously edit-challenged - with up to 10 levels to deal with.

Having said that, especially your points 1, 2, 4 and 5 are most valid.


Oh bugga! I'm supposed to teach Am'rican Hist'ry and Practical Maths to avoid the wrath of newbies, ignoramuses and Western Australian carport extension designers...

Right-o, here we go: cover the offending hole with a polygon and say "Add surface" and presto, it's gone! That should be easy enough for all other mentioned groups than the Western Australians.

Edited by Petri
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I use Petri's method to remove voids in the poly, very efficient.

I wouldn't care to have each modified 2d poly carry with it it's history of clipping, adding, etc. I think it would add too much overhead to the file size. Besides that, if you notice, 3d boolean objects are no longer extrudes, they are a different object type (a necessary complication, if you think about it). So if your idea were implemented, once you clipped a 2d poly it would then become a different object type and couldn't be clipped or otherwise modified with 2d reshape, etc.

With Petri's method and with multiple-vertex reshaping, I think there are sufficient methods to deal with the issue. And a solid subtraction isn't a bad way to go, by the way. Just extrude all your holes or cutting shapes at once to make a single subtraction solid. Then you can add to, subtract from, or edit the set of 2d objects to make changes in your hole pattern. I do it all the time, and no complaints!

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Thanks all - for providing several ways to do the edits without need for reengineering the clip surface to carry along its formation history as I suggested. Always more to learn!

I still think that users will benefit if the command includes a way to access the interior verticies through the OIP. Perhaps a mode option in poly edit for mouse click to indicate which vertex I want the IOP acknowledge.

Also, I find that after many clips are made into a surface, additional clips may delete or alter previous clips. If this is common experience, the command needs reworking.


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