small surfaces

[hoover33]

I've been doing a lot of surfacing using ISDX and have found that when I get to smaller surfaces in the model they don't always behave as they should. I am trying to fill in a "gap" in a surface model using the style tool. I can't really post a good picture or model due to the nature or the work, but I can say that I know what I want to do is geometrically possible. But when Pro constructs the surface it is all rippled and refuses to merge or thicken. My gut tells me that on a much larger scale I would have no problem here, since I only usually run into these problems on a small scale.


Is there anything I can do to make these surfaces construct better?

 

[appinmi]

Sometimes changing your accuracy to .0001 will help with smaller surfaces.

 

[hoover33]

Is this the option "accuracy_lower_bound" or "default_abs_accuracy", or something else? Both of those are already set at .0000001.

 

[appinmi]

On the top toolbar, select Edit, Setup. Then in the "PART SETUP" dialog box, select Accuracy. This is the part accuracy which defaults to (.0012). If the distance between vertexes or edges is equal to or smaller than this will cause a problem when creating geometry. If you set it smaller, it allows for smaller surface creation.


Imagine if you were trying to do a cut that is only .001 deep. Proe cannot create this cut because of the accuracy. In my startup file, I have the accuracy set to .0001 by default. This creates a larger file size, but eliminates almost all of the "geometry checks". Adding rounds seem to be easier and it will also create better "step" or "iges" files when exporting.

 

[hoover33]

Hmm. I actually solved my "small surface" problem by another method (eliminating the need for the small surface). But I was curious about the accuracy thing so I played around with it.


We're talking about the "relative accuracy" setting, right? (choice between "relative" and "absolute" when I follow your directions)


I first tried .00001 (I figured I'm 10 times better than you

) but that caused some very simple features (rounds) to fail, features which worked fine at the .0012 setting.


Then I tried your recommended .0001 setting, and some style curves failed, but this is very common I've found and all I have to do is click the "unlink" buttons in the failure resolve thing and then they work fine again (a strange quirk in the style tool). It worked and the filesize did indeed increase largely. Didn't seen any huge changes in my model but then again I don't have any small surfaces now since I eliminated the one set I had.


Thanks for your advice.

 

[appinmi]

You won't visably see much change in the model. What does change is the accuracy of all surfaces. This requires a lot more data, that is why the file size changes and is why you get more accurate exported files.

 

[hoover33]

What's the diff between relative and absolute? Any idea why I'm seeing failures when changing these to smaller (ostensibly "better") numbers? Changing relative caused rounds and style features to fail (I was able to repair the style feature) and changing absolute caused a swept blend to fail (not able to repair that one either).


Thanks again.

 

[appinmi]

If you are changing to "absolute", I cannot help you because I never have used it. If you are changing to "relative" when you get this problem, then I might be able to.


When features are created, Proe uses the "accuracy" to try and "fit" the surface if it doesn't exactly match. What I mean is a surface can vairy

 

[dojo]

When modelling plastic parts, or work with skeletons which are 'large' in size, always use absolute accuracy. You'll have less problems with rounds, with gaps, with curve endpoints not lying close enough to each other to form a closed boundary etc. Just put your start parts on absolute, and you will work more troublefree. Changing from relative to absolute mid modelling i would not suggest or you could get a weird outcome like features not regenrating anymore.


Relative accuracy is related to the coordinate system, when you create a part which lies far from the coordinate system (for example a roof for a truck where the default coord system is on the rear transaxle) you'll notive that the gaps between surfaces are becoming larger the more complex your model is, that rounds just dont work, that composite approximate curves are not continous although they are created etc etc.


I think absolute is per feature and defines the accuracy of that feature based on its own size. (dont shoot me if the explanation is wrong, its just out of experience what i tried to explain)


Also aiding with troublesome parts in relative acc. is adding 3 tiny tiny curves along x y & z at the start of your model


All our start models and assemblies are set to abs. accuracy of 0.01


Regards,


Nick

 

[hoover33]

Thanks Nick, the "3 tiny tiny curves" idea sounds pretty clever, I'll give it a try.

And Allan thanks again for your help. As I said before, I can't upload any files due to the proprietary nature of what I'm working on.