Bug - Snapping lost

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 From:  PaQ
2120.1 
Ok, sorry if it was allready reported, or if it's 'normal' and I just miss something (I'm a bit tired ;))

I just want to create a circle, using the existing center circle 'trimmed' in the model.



but after clicking on the center snap, none off the snapping element work when I try to define the radius.



Hope it's clear enough ;)

EDITED: 4 Dec 2015 by PAQ

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 From:  Frenchy Pilou (PILOU)
2120.2 In reply to 2120.1 
Why not use a simple "Helper's line" as diameter : middle is automatic ;)
So circle can be drawn :)
Damned a little more complex I had not seen that surface was curvated!



System of Helper's line is terrific in Moi!

But of course maybe a bug should be escaped :)

PS It is a new model of Football shoes? :D

EDITED: 28 Oct 2008 by PILOU

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 From:  Michael Gibson
2120.3 In reply to 2120.1 
Hi PaQ - that's actually normal behavior, it is part of the new "direct drawing on surface" functionality for v2.

When you snap the center point of the circle on to a surface, it will take on the orientation of that surface and snaps off of that plane will be suppressed. If they were not suppressed you would not have a very natural circle drawing method because of all the snaps getting projected down to the plane cause the circle to jump wildly in size instead of moving smoothly in size when you move the mouse.

This suppression only happens in the 3D view, you could probably get what you want by setting up a CPlane and then using the Top plan view which will not have snaps suppressed.

It could help me understand the problem some more if you could show the desired result that you are looking for.

- Michael
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 From:  Frenchy Pilou (PILOU)
2120.4 
Curiously in the case of PaQ snap works on new other circles drawn!

EDITED: 28 Oct 2008 by PILOU

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 From:  PaQ
2120.5 In reply to 2120.3 
Hi Michael

>> When you snap the center point of the circle on to a surface, it will take on the orientation of that surface and snaps off of that plane will be suppressed. If they were not suppressed you would not have a very natural circle drawing method because of all the snaps getting projected down to the plane cause the circle to jump wildly in size instead of moving smoothly in size when you move the mouse.

Make sence, I didn't notice it earlier so I was surprised :)

>> This suppression only happens in the 3D view, you could probably get what you want by setting up a CPlane and then using the Top plan view which will not have snaps suppressed.

Thanks for the tip, I'm not used yet about the cplane hehe

>> It could help me understand the problem some more if you could show the desired result that you are looking for.

For that example, I want redraw the 'trimmed' circle by a new one, to create some fillet manualy (using the donut boolean technic).
Sorry for the trouble, I should not post so late after a long working day :)

EDITED: 28 Oct 2008 by PAQ

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 From:  Michael Gibson
2120.6 In reply to 2120.4 
Hi Pilou - yes that is normal for the first point, the first point of a circle can be snapped on to any snap point as per normal.

But if you have picked a first snap point that aligns the circle to a surface normal plane, then the second point will ignore snaps that are not on that same plane (while picking in the 3D view).

Otherwise if it did not do that, there are 2 other choices -

#1 - allow any other snaps. This has a bad consequence of basically eliminating the ability to sketch a circle normal to a surface because you'll get a whole bunch of snap points such as "on srf" ones that would be off of that surface normal plane.

#2 - allow any other snaps but project them on to that surface normal plane. this allows for drawing the circle aligned normal to a surface, but tends to cause major jumps in the size of the circle as snaps on the back side of the model are targeted and projected to the plane.

I could possibly incorporate some setting to avoid the suppression, but it would help if I could see what is the desired final circle in this particular case.

- Michael
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 From:  Michael Gibson
2120.7 In reply to 2120.5 
Hi PaQ, it's no trouble, and it is helpful for me to know when some of the new v2 things are causing confusion in certain situations.

Can you possibly post the model so I can take a look at your trimmed circle?

If that trimmed circle is on the same plane as the center point you snapped on to, then it is supposed to snap on to it, so that could be a bug or perhaps a tolerance issue where I'm using a slightly too tight tolerance to suppress off-plane snaps.

It may be something that I can tune up if I can examine the case more closely.

EDIT: Oops, I see that you did post it, I'm not sure why I didn't see that, I will take a look.

- Michael
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 From:  PaQ
2120.8 In reply to 2120.7 
So My goal here is to rebuild a donut, so I just want to rebuild a circle as a sweep path for a donut, to have something like that :



Because if I use the existing trimmed one a have more section in the donut, and I want to keep it clean for the boolean I wan't to do later.



Again, it was more a 'surprise' that I can't snap the circle radius after picking the center (in the 3d view), but I fully understand why now, and it's not a problem anyway ;)

Edit:

Maybe you could rename the thread to something like 'snapping question' ... there is no need to have bug alert for nothing :)

EDITED: 4 Dec 2015 by PAQ

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 From:  Michael Gibson
2120.9 In reply to 2120.8 
Hi PaQ, on closer examination it looks like there is a bug in here.

It actually should not be trying to align to the surface normal in this case at all, because the center point of that trim edge is not actually on the surface.

This case of an edge being an exact arc but the surface not being planar is not being handled correctly right now. It assumes that the center point of the edge is on the surface as it would be on a planar surface like a disc, and it is getting the surface normal at the closest point on the surface to the edge's center point.

It should not be aligning to the surface here at all, it should either not try to align it or it could align to the plane of the trim edge instead which probably makes sense.

I got a little confused from your initial image because I thought there was a filled in planar disc there instead of just a hole. And actually if you put a planar disc in there the snaps on a disc like that will work as you were expecting.

I'll see if I can fix this up, I think once it is fixed it should behave in this case as you originally expected if I can add snap plane alignment to a trim edge on center snap.

So thanks for reporting it, you can see an even more striking instance of this same bug if you draw a cylinder, rotate it around to an odd angle, then delete the planar end caps and draw a circle snapped on to the edge's center in that case. Since the closest point to the cylinder is way far off it is a more noticeable effect. It was kind of masked previously because it was handled fine if the cylinder caps were in place.

- Michael
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 From:  Frenchy Pilou (PILOU)
2120.10 
Yes but if I want stop my circle at a point of this curve line intersection ? ;) (button and the planar circle)
I must make the intersection first for have a point!
So draw twice the circle ;)
But maybe your previous post crossing answered this problem

EDITED: 28 Oct 2008 by PILOU

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 From:  Michael Gibson
2120.11 In reply to 2120.10 
Hi Pilou,

> I must make the intersection first for have a point!

Yes, that's correct - you could either boolean or trim those surfaces to create an edge there, or you could use Construct / Curve / Isect to create intersection curves between them.

It's not really feasible to do an automatic surface/surface intersection for snaps, it is just too slow and processor intensive to attempt to do it between all surfaces automatically. It would make for very slow interaction while you were trying to draw.

- Michael
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 From:  Frenchy Pilou (PILOU)
2120.12 In reply to 2120.11 
I Understand :)
---
Pilou
Is beautiful that please without concept!
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 From:  PaQ
2120.13 In reply to 2120.12 
>> So thanks for reporting it, you can see an even more striking instance of this same bug if you draw a cylinder, rotate it around to an odd angle, then delete the planar end caps and draw a circle snapped on to the edge's center in that case. Since the closest point to the cylinder is way far off it is a more noticeable effect. It was kind of masked previously because it was handled fine if the cylinder caps were in place.

Ok, happy (if I can say) to find this one :)
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