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Re: The thread for silly Alias questions...

Postby Cyberdemon » March 24th, 2012, 12:23 pm

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Modelling 1/4 is fine - but if it's giving you that result it more than likely means that where your gen curve is not G2 across the curve you are trying to create G2 across.

If you can post a screen shot of your 2 curves with the orthos and the CV's on, you can probably see one CV isn't lining up across your second symmetry plane.

Re: The thread for silly Alias questions...

Postby eobet » March 24th, 2012, 1:34 pm


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Curves are made sure that the 2nd CV is aligned to the 1st. I've repeatedly snapped them and they seem fine.

Still, no go.

So, I remember that if the 2nd CV is normal to the mirroring plane, I only need tangency to get curvature across the surfaces.

Still no go.

As a last ditch attempt, I duplicate the curves off the failed surface, set up support surfaces and create a new square.

Again, no go.

Anyway, this was an exercise and not really needed for my final model. I'm going back to modelling 1/2 of it instead. Still weird, though.


EDIT: Going really overkill and making sure the 2nd and 3rd CVs were aligned in both corner curves, then duplicating these to form the other corner and building a square with implied tangency(!) from those did produce a proper curvature aligned mirrored surface... but man, why couldn't it just work from the start? :P

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Right but remember when you are sweeping a curve, the rail it moves along wants to rotate that curve in such a way that may cause the CV's in the opposite direction to no longer be where you think they will be. When you force them to, it can break the continuity along the opposite plane because of that transformation.

I model stuff in quarters all the time, you just need to make sure the curves you start with want to allow that.

Re: The thread for silly Alias questions...

Postby eobet » March 25th, 2012, 4:20 am


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Ah, right. Thanks!

So next I should go looking for the equivalent of "keep normal constant" from Solidworks's sweep feature. :)

Anyway, looking back to the first question of the first page is really a facepalm on my behalf. :D Not since that first page have I ever needed to do what I asked about. One should really not be allowed to use Alias without taking a few courses first (which is a statement which really takes an effort for me to write, being a former interface designer).

Re: The thread for silly Alias questions...

Postby eobet » May 1st, 2012, 10:13 am


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I think I may have screwed up a setting, and I can't find it.

When I align two surfaces, and then start moving the controlling surface's CVs around, the aligned surface's CVs slide alongside the edge freely (see attachment).

This differs from the behavior when I've straight up built one surface from another (the CVs along the edge are locked on top of each surface then), and I want to get back to that behavior.

The positional influence is 1.0, so what other setting am I missing?
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If you build a surface off an edge, it uses that edge as is (CV's should be locked on top of each other).

If you align something to an edge, and then start to move something, it will allow them to move differently as long as it achieves the requested tolerance.

I'm not sure you'll ever get to what you're asking, but I'm not 100% sure if I follow why you'd need to?

Re: The thread for silly Alias questions...

Postby eobet » May 1st, 2012, 1:05 pm


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Because I did not know about the option I just found, and tried to achieve it manually for DAYS now:

The colinear continuity option.

God DAMN!

Why isn't that enabled by default?

The only reason I found it was that I enabled the patch precision drawing of curves within a surface, and evaluated their continuity and discovered that they were really breaking, despite the surface coming up as green, and even the shading lining up (although with bumps which I could see in the CV mesh, but didn't know now to straighten out without turning to manual tweaking... and hence me dabbling with various align options which enabled me to retain some of my tweaking).

The levels of complexity to be discovered behind every option in this software is just mindboggling.

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Keep in mind the continuity indicators that turn green only indicate the boundary is within tolerance. If you are using the wrong tolerances (IE tolerances that might be OK for a truck, but not a handheld product or vice versa) you'll either wind up never getting continuity (without heavy complexity) or you'll have a false sense of continuity.

Re: The thread for silly Alias questions...

Postby eobet » May 1st, 2012, 2:03 pm


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Unless I managed to screw up my settings, I believe I'm using tolerances of car body fidelity:

Max gap: 0.005mm
Angle: 0.1 deg
Curv: 0.1

(Got them from my teacher in alias and he did car industry work.)

EDIT: It just hit me that I'm designing a toy right now, that measures in millimeters instead of meters...

Re: The thread for silly Alias questions...

Postby engio » May 2nd, 2012, 1:43 am


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Cyberdemon wrote:Keep in mind the continuity indicators that turn green only indicate the boundary is within tolerance. If you are using the wrong tolerances (IE tolerances that might be OK for a truck, but not a handheld product or vice versa) you'll either wind up never getting continuity (without heavy complexity) or you'll have a false sense of continuity.


Interesting, do you have the applicable tolerances for handheld products? Any others would be useful as well.

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engio wrote:
Cyberdemon wrote:Keep in mind the continuity indicators that turn green only indicate the boundary is within tolerance. If you are using the wrong tolerances (IE tolerances that might be OK for a truck, but not a handheld product or vice versa) you'll either wind up never getting continuity (without heavy complexity) or you'll have a false sense of continuity.


Interesting, do you have the applicable tolerances for handheld products? Any others would be useful as well.


Tolerances are a bit of a beast with a few things to consider:

1: Scale of what you are designing
2: CAD Software your data will be translated to.

I use the default Pro E settings (since I am translating to Pro E) but have modified the curve fit and maximum gap to .001mm from .002 - have found some small surfaces get gapped when importing otherwise.

Re: The thread for silly Alias questions...

Postby eobet » October 26th, 2012, 7:15 am


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So, Alias fun again!

This time, I managed (I think) to screw up a file, and in the process, I've discovered that there actually several different kinds of pivot points in Alias. The problem is, in their explanation on how to move them, they forgot to mention that there is more than one type.

So, now I have a file, in which they move separately for some reason I have not been able to figure out. I also have not been able to figure out why this happened in the first place, or how to get it back to the behavior I've had for the past three years (and no, it's not in the Pivot tool options, where one would think to look).

Anyone ever had this happen to them? How did you get the normal behavior back? Where did they hide those options?
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Re: The thread for silly Alias questions...

Postby Cyberdemon » October 26th, 2012, 8:22 am

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So I've never ever had that happen, but it looks like you somehow managed to separate the scaling and rotation pivots.

When you go to any of the move pivot, set pivot or any of the pivot command option boxes there should be a checkbox for "Rotation and Scaling" and they should both be checked. Then if you center the pivot it should put them both back at the same point.

I'm not sure how you got that to happen, the only reason I could see it moving that geometry is if you have some construction history on that surface that is related to the pivot (like a revolve for example).

Re: The thread for silly Alias questions...

Postby eobet » October 26th, 2012, 8:54 am


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Thanks for the reply, as always. :)

When both are checked, they move at different speeds. When the scaling pivot option is unchecked, the small round pivot moves without affecting the geometry. However, whenever the scaling pivot is checked, the geometry moves with the pivot. The surface does not have construction history and it doesn't matter if I cut and past it into a new file.

If I, however, start from scratch, the same thing doesn't appear to happen. Also, even if I press "zero transform" and then duplicate the surface using the "duplicate object" tool, it gets seemingly non proportionally scaled by more than half of its original size. Luckily, I did manage to figure out that if I pulled an old Solidworks trick and used offset surface with a distance of 0.00, I got an identical surface and so far, that seems to have resolved it!

What can I say? Alias... :)

PS. I recently accidentally deleted all my preferences and had to transfer them again from my old OS X install, like I've done many times before. Only this time, whenever I launch 2013 I must manually make the shelf appear from the Windows menu, and I can no longer create curves using the "cv curve" tool, because they get locked in a -1 span setting, so I have to use edit point curves instead... I tried to go back to 2012, but that no longer allows me to save my settings and always complain about it when I try to exit the app.

Re: The thread for silly Alias questions...

Postby Cyberdemon » October 26th, 2012, 10:45 am

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Honestly not sure on any of that.

You should have been able to just center the pivot to put the scale/rotation pivots back at the same point.

Without looking at your wire file it's hard to debug why something is behaving a certain way. Also keep in mind groupings or construction history can cause things to freak out. Try deleting your construction history and making sure your node is completely ungrouped and then see if you still get strange results when duplicating. You may have an operation (projection, trim, etc) that's causing your issues because it's doing something weird in the background that you've forgotten about.

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