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jbrhwy

Polyline Problems Remain in VW2009?

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I am starting a new post for this item in General Discussion as there has been no response to my previous post.

"Does the new arc tangent mode solve a long standing problem with Vectorwork for 15 years I have been requesting an additional vertex method that would insert a symmetrical curve between two intersecting lines that is not constrained by an artificial mid-point. The current problem is if the tangent distance of 1 curve is greater than 1/2 the distance between the intersection points , VW moves that vertex (disaster)".

As a road designer arc polyline objects are the basis of my work; most drawing objects are parallel offsets from the design road centre-line (curbs, sidewalks, pavement, etc & these objects are combined to create a filled surface). Because of the limitation above, the only way the correct arc can be obtained is by regressively adding a vertex at the mid-point, very tedious exercise & has to be done for every offset polyline so they remain parallel. I will not comment on the nightmare that occurs when I have to revise the design road centre-line. All I want is the ability to place a symmetrical arc, change it's radius when necessary, between intersecting lines. This is how roads are designed. Road design & COGO software are not controlled by a mid-point vertex.

I have posted & sent tech support numerous drawings with this problem, I will post another file demonstrating this problem if needed.

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Frank

I did looked at the movie the day that VW2009 was released & it appeared that the offset polyline had added additional vertexes! After using this product since 1990 I find your remark very condescending, all you had to do was draw a polyline with the above condition to determine if 2009 had resolved the problem.

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The attached file "Polyline problem.mcd" shows that it takes 5 steps to be able to have an arc radius of 80 metres for the first intersection point. If the first radius needs to be changed then the polyline has to be redraw if the required radius is greater than 61.801.

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Bruce,

I'm not sure I understood your problem. For polyline #2, I would just use the 2d reshape tool to convert the intersection point into a corner point. The next step would be to use the fillet tool to get the 80m arc. No redrawing necessary.

I came up with a polyline with more vertices than what you had in polyline #5 though.

Ariel

VW2008 SP3

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Ariel

I think the steps below sent to Frank Brault will show why 5 steps are needed to use the reshape tool.

Yes the fillet tool will work, but you would have to use it twice & reset the radius preference & then end up with 8 vertexes instead of 5. If you need to revise the first radius to 90 metres you can not do it because Vectorworks inserted corner vertexes & if you delete them to change the radius, the PI (intersection point) moves. This defeats the original requirement to have total control of placing a radius between intersecting lines. Now try use to Offset tool to set the edge of curb at 4 metres, the first radius becomes 83.615 not 84 & the second radius becomes 23.875 not 24.

"Frank

1. Connect road intersection points using polyline tool, all roads are designed from points of intersection & bearing to the next PI.

2. Change vertex corner points to arcs, the first will not accept the required 80 m radius, defaults to 61.08, the second one is changed to a radius of 20 metres.

3. Add a default corner vertex between PI1 & PI2.

4 Add a default corner vertex between the corner vertex created in step 3 & PI3.

5. Delete the corner vertex created at step 3 & now the radius of the first curve changes to 80 metres.

The problem with this is that, if the design radius has to be changed then you have to start all over again because of the corner vertex placed at step 4 will not change with a new radius.

What is required is mode that allows placing an arc between intersecting tangent lines.

The Road tool has the same problem you can not create a road where the tangent distance of the curve is greater than 1/2 of the distance between the PI's.

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Bruce - Sympathy for the problem with the poly arcs. Ignore this if irrelevant, because I do not exactly understand laying out roads from PIs. But I am not sure that after all your machinations, you actually achieved tangency and coincidence between your two arcs. My drawing shows your orig lines and final poly in pink. I added angle bisectors and tangent arcs in blue and green using point A as the start.

Point C1 is your corner point btw your two arcs.

Anyway, if you strike a 3 point arc on top of your 80' radius arc, it does pass through point A, but does not pass through point C1. It does have center on the angle bisector. Perhaps there is a straight segment in there?

No need to school me on road layout, I assume you know what you are doing, and I do not. I just thought your final poly did not look quite tangent.

-B

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Benson

Thanks for taking the time to look at the problem, yes there is a short section of tangent between end of the first curve & start of the second curve. When I check the coordinates of PI's against the coordinates of the arc vertexes they are the same & the bearings to each PI, therefore, tangent.

Did you look at what happens when you try to offset the polyline?

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Right, Bruce - I guess your starting arc PI is not actually on my point A, but rather up the leg a bit. Decompose your final tangent poly (pink) to reveal two arcs and 4 straight segments. Offset your poly and, as expected, find two arcs and a bunch more straight segments (blue). That cluster of 3 new segments between the arcs destroys your curve/line/curve tangency, although the end segments seem tangent top the arcs.

As oft noted, any operation (split, extrude, etc) on an arc poly places corner vertices on all those interstitial line segments which were hidden during poly creation. Offsets don't hide the straight segments.

Maybe the VW2009 arc poly modes can be of help. Anyone apply it to this situation yet?

-B

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Has anyone had the opportunity to check the result of offsetting the polyline created at step 4 in version 2009, is the resulting offset polyline no longer parallel to the original? Note: the polyline at step 5 can not be offset correctly with the Offset tool, but is correctly offset when using Manuel Garcia de Paredes Offset Path tool!

Benson

The problem is not unique to designing roads, any polyline with more than 2 arcs where the tangent distance of 1 arc is greater than 1/2 the distance between the intersection points can not be offset correctly & there is no warning that the new radii is not what was set in the preferences.

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Just got back from a VW 2009 conference. Sorry, if what I am going to dewscribe is not what your issue is but I would post in case it was.

We were shown three examples of the extra detail and accuracy that Parasolid would give when offsetting 2D polylines with the offset tool. As far as I could tell, 2009 got them spot on, where as the 2008 examples the lines drifted or even kinked in what could only be described as a non uniform path.

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Hello Ian

Discussions regarding this problem are ongoing with Frank Brault of Vectorworks, but it appears Vectorworks 2009 doesn't address this problem & possibly never will be able to.

In the mean time I am attaching a design drawing HPGCTerasen.mcd that shows how dependant I am on the polyline objects & will demonstrate the magnitude of the problem if I have to increase the radius of only 1 curve due to a design change. All polylines would have to be redrawn.

Thanks to everyone for bearing with me on this issue, but I have spent thousands of hours trying to work around this limitation.

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Bruce,

Unless I misunderstood the problem, from what I can tell in examining your file, VW2009 is able to work perfectly well.

I opened your file in VW 2009, selected the road centerlines, and offset them (pick-drag) on top of the road edge you had drawn. The new offset lines matched perfectly.

The new Parasolid engine adds much greater fidelity to 2D offsets and boolean operations.

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Jeffrey

Thanks for looking at the file. What happens in VW2009 when you try & increase the radius of one of the arc vertexes using the object info pallet? In all previous versions it is not allowed even though it is mathematically correct, the "quietly placed extra vertices" prevents increasing the radius & the only work around is to delete the extra vertex & then add recussive vertexs until the new radii is accepted.

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Bruce,

This does appear to be the case. I would add to the Wishlist forum a desired Polyline mode and offset behavior for your desires. I understand your issue and see its relevance, especially for road layout.

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Bruce,

This does appear to be the case. I would add to the Wishlist forum a desired Polyline mode and offset behavior for your desires. I understand your issue and see its relevance, especially for road layout.

Um ... according to the OP, he's been requesting it for 15 years ... seems like it should have been addressed by now ...

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Bruce,

This should be a simple task for NNA and do not understand why it has not been fixed yet. As a road designer myself, I abandoned the idea of using polylines because offsets were converted to polygons back in VW 11. I opted to work around this limitation by using simple lines and arcs and composing segments into a polyline if needed. I say it should be a simple fix because I have created the scripts to calculate and draw the offsets using vector math which is included in their script language. I do hope NNA gets it right in the next service pack because it is long overdue.

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This feature now works perfectly in 2009, as the 2D operations in Vw now benefit from the Parasolid engine.

True offsets are now created instead of getting polylines that are not only incorrect but also with multiple extra vertices.

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M.CH

In VW2009 when you attempt to increase the arc radius of the polyline where the tangent distance of 1 arc is greater than 1/2 the total distance between the points of intersection - due you not get the error message "The arc radius is set to the maximum radius allowed" even though the selected radius would be mathematically correct?

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I opted to work around this limitation by using simple lines and arcs and composing segments into a polyline if needed.

ditto...

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