# Offset surface with errors

DELFTship forum Hull modeling Offset surface with errors

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Posts
• #44563
Felsentreu
Participant

Hi,
I have a small problem with the function “Offset surface”.
Some points have different values. A new point at the stern deletes the mark of the corner point.
See attachment.

Greetings

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• #44566
Terrance Egolf
Participant

Welcome to the wonderful, exciting—and unpredictable—world of the Offset Surface!

I don’t pretend to understand the mathematics underlying DELFTship’s surface modeling engine. However, I have attempted to do the same operation on a similar hull as well as some experimenting and the results were less than spectacular or expected.

Any location in your model’s surface where there is a fairly significant change or discontinuity in the orientation of the surface normals, you can expect some unusual behavior of this feature. For example, I have found that along the centerline of the model (y = 0), the new offset points will tend to wrap across the centerline in the –y-direction, as if the engine is trying to accommodate the average direction of the surface normals at this discontinuity.

Elsewhere, if you have crease edges intersecting at corners , or in close proximity to each other, the resulting offset surface can be really bizarre.

Here is my example that I faced in my brigantine model. This shows the moulded hull and transom. The transom is on a separate layer.

Next, I turned off the transom so I can just offset the hull surface by 3 inches/0.25 feet (sorry, I’m in the US).

Then I offset the selected surface (I don’t think it’s necessary to actually select the surface; the dialog has you offset the selected layer.):

So you can see the nasty details where the rail line converges on the transom.

All I can tell you is that after offsetting the surface, you should expect that you will need to do some cleaning up especially around edges that change direction or shape.

Terry

PS: The program puts the offset surface in the layer at the top of your layers list for some reason, so if it doesn’t appear after commanding the offset, then look in that layer, especially if it’s turned off.

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• #44571
Maarten
Keymaster

Interesting.. Offset surface is not a feature that we use often, but it seems quite unpredictable indeed.

I hope we can find the time to look at what happens, and why, and maybe include a fix in the next release..

• #44572
Felsentreu
Participant

Hi,
@Terrance wrote:

Welcome to the wonderful, exciting—and unpredictable—world of the Offset Surface!

Thanks for the welcome!

PS: The program puts the offset surface in the layer at the top of your layers list for some reason, so if it doesn’t appear after commanding the offset, then look in that layer, especially if it’s turned off.

Good hint, I was looking for a way to put the surface on a new layer.

Interesting.. Offset surface is not a feature that we use often, but it seems quite unpredictable indeed.

I think this feature is probably mostly used by your fan community of model makers.

Greetings

• #44574
john truelove
Participant

Sorry guys, this is off topic but I cannot find a relevant topic and I am getting desperate.

I am taking off construction drawings from  a delftship model using the “print” command in the lower rhs of the menu ribband, then entering the image into libredraw and adding text.  This worked well on a previous project, but now when I try to print a front view / port side only (say to give a traditional body plan: bow to the right, stern to the left) I get an error message “invalid enumerator” and the program freezes.  Crashout and start again.

This appears to be occurring only since I last updated the program.  Relevant circumstances are

1.  front view
2. wire frame (?)
3.  showing one side only

It may relate to the stations/waterlines/buttocks grid as entered by “intersections”.  Sometimes deleting these enables me to print, sometimes not.  Sometimes reloading the model appears to carry with it the error othertimes it does not.  The stations input seems the worst offender.

I have been able to proceed via prtsc>Paint.NET>LibreOffice Draw but it is a clumsy way of doing business

Can anyone tell me what “invalid enumerator” means and suggest a way ahead?  PLEASE!

Jaytee

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• #44576
Terrance Egolf
Participant

Hi jaytee.

I just installed v. 14.20 (342) of the program and tried to duplicate your problem with my own project file. I got nothing unusual. (See the attached Print pdf.) The only difference between my situation and yours is that I have moved the midpoint of the model in Project Settings about 50 feet aft of the AP. I did this so I don’t have issues trying to move control points in the Front or Aft views, but I also only get one side of the hull in these views with Both Sides turned off.

It may be an issue with your .dbm file itself. I suggest you submit it to Maarten so he can evaluate it.

Terry

DELFTship-Front-view

###### Attachments:
• #44579
Maarten
Keymaster

Hi JayTee,

I can also not reproduce the error you are reporting. What version are you using?

Is it a structural problem? Does it happen in other projects?

• #44580
john truelove
Participant

Thanks for replying Maarten.  As I have just responded to Terry , I am using version: 14.20 (341).

There is another update that I have yet to install, I have tried but (I think) got called away and forgot about it – I presume that would raise my version to 342.

John

• #44881
Anneler Ruedi
Participant

Hi

is there anything new to this? I’m running version 350 Pro, and I have strange results from trying to use offset surface too. Check Model shows no errors. Offset surface produces wrong locations of the lower points a both ends of the strake (see attachment). I tried to offset + 10 mms to the outer side, and -20mm to the inner side. The directions of the offset are correct, but the lower control points at both ends of the strake are not. Can please someone have a look on this and fix it? The function could be useful to e.g. find plank landing points for a lapstrake hull.

Besides this I dislike the behaviour of “Offset Surface” to attach the newly created surface to the very first layer in the layers list. I’d prefer to have the option to define the target layer by myself – or, if done automatically, the creation of a layer qwith the same name as the origin used for “Offset Surface” with a suffix, e.g. “inner”  / “outer” or something else letting me know the origin and the direction of the surface I’ve offset.

###### Attachments:
• #44884
Anneler Ruedi
Participant

Any ideas to this? Plaese let me know. Thank you.

• #44888
Marven
Keymaster

The new surface is created using the surface normals of the old surface. The new surface will be incorrect when there are errors in the calculation o the surface normals.

• #44889
Anneler Ruedi
Participant

Marven, thank you, and yes, I know. Are there any errors of this type in the Delftship file I’ve attached? If yes, which ones, and how can I get rid of them, please? “Check Model” does not show any errors.

• #44896
Marven
Keymaster

Hi Anneler Ruedi,

I’ve checked your file and it’s just fine. It helped us to identify what caused the problem and we have fixed this for the next scheduled release. See also the screenshot below.

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• #44900
Anneler Ruedi
Participant

Dear Marven,

great service, many thanks for your quick and useful action and response. Your kind help is highly appreciated!

Ruedi