projected points don't maintain a linkage?

[Anonymous]

I ran into an interesting case yesterday. I'll admin that I'm a tinkerer and hobbyst, so my knowledge of Fusion is closer to whatever I need to achieve a particular project.

I was working on an element with a 4-sided point. A square, extruded to a cube, then lofted to a point which is in the center of the top face. Sorry I don't have a video of the design, but it is really simple.

All well and good. I create a point centered via creating a corner-to-corner line in the first sketch, using the midpoint constraint to create the point in the center (let's call this the centering point). Then I can create the construction plane a distance above the top face, sketch on that, then project the point to the sketch (let's call this the loft point), close the sketch, and loft the top face to that point. All good.

When it comes time to change the design a little - love that parametric modeling, because I keep screwing up! - I go into the original sketch and change the base, and I see the center point stay in the center of the original square, but when I closed the sketch and the timeline rolls forward, the loft point doesn't move, so the "tip" of the loft stays in the old location and is asymmetric. Thus, the link between the "loft point" and the "centering point" doesn't exist, and this surprises me. ( I know there's an option to turn it off, I didn't do anything but the default when I projected ).

I found a bunch of ways around this. The cleanest seemed to be projecting the entire square of the original sketch, then in the destination sketch draw a new line and center point, those maintain their link. I might have found a more minimal method by projecting only the "corner to corner" line, but it's basically the same idea - the line geometries are keeping their linkage correctly, when the points don't seem to. I also found cases where my "corner to corner" line wasn't constrained properly to the corners in the first sketch, thus the source point wasn't moving right, but that's what learning Fusion is about!

Is there some way I should think about this, to better understand Fusion? Did it matter what kind of lines or points I was using ( construction vs regular )? Is it a matter of points vs lines maintaining links while projected? Or is it supposed to maintain a link on points like this, and I messed something else up?

Using this project ( like many others 🙂 ) to better understand fusion, so look forward to that kind of discussion, as I've already figured out how to do what I want ( project lines not points ), just interested in some insights.

(Version is whatever "latest" is, I saw a new release roll in a few days ago. OS is Win10 if that matters.)

Thanks!

[davebYYPCU]

Simple or not, you are asking about unexpected behaviour.

We need to see how you got to that point with file or screencast.

That said, Projected points should be associative.

Where is the Document Origin in this simple example, centre of the cube or in a corner?

Loft to a point symmetric, use the Origin to be centre of the cube, can’t go wrong.

Couple more things, second sketch does not need anything other than the projected point.  Should be a purple point in my colour scheme.  

project with or without linking, is likely culprit, it is a toggle switch will remember last setting, so relying on default is not a good move.

Might help....

[laughingcreek]

I had a hard getting through that rather long description.   you can take screen shots with "shift-windows key-s" key combo.  you can also go to the file menu and export as .f3d to attach example models.

Your various descriptions of how you achieved your shape sound like you are taking more steps than necessary to achieve your goal.  more steps=more chances to screw up.

Let's see what your doing.

[Anonymous]

Thanks for the tips! Sounds like it should work, I'll look for the colors, and see if I can get a screenshot, and look at executing the project operation without defaults to see if they are linked.

The simpler mechanism of using the center of the cube for the projection makes sense; I'll see if that has the same behavior that I observe by using the center of the square in the sketch used to create the cube. They both should obviously be equivalent, the center of the sketch makes slightly more sense to me logically, but I should be able to master projecting in all the cases (since this is about learning).

I am sure there are simpler ways, and will see if I can put some screenshots together. I haven't built the tech to do a video from my screen yet, but I'm just fine with screenshots.

[laughingcreek]

a lot of us use this to produce screen casts.  it's nice for trouble shooting b/c it captures key strokes and mouse clicks.  and all the commands used are shown along the bottom.

https://knowledge.autodesk.com/search-result/caas/simplecontent/content/download-autodesk-screencast...

[Anonymous]

That program doesn't install on my version of Windows 10. It says a version of some particular microsoft library wasn't installed.

However, you've shamed me into getting hip with the screen video. Turns out the Xbox Game Bar does this, and pretty well too. Will follow up with video.

[Anonymous]

Here is a screencast of me doing the operations. It's not an autodesk screencast because that software did not install correctly on my machine, I got DLL errors when it tried to launch.

https://www.youtube.com/watch?v=Gn67mbrTkRU

The audio should be explanatory. I create a basic sketch and a rectangle, and put a point in the center. I get out of the sketch and extrude the rectangle into a cube. I create a point in a new plane projected from a point was in the first sketch, and loft to it. Then I decide I want a different size box, so I go and move the initial rectangle, expecting the point in the first sketch stays centered ( it does ) and but finding the projected point does not move, so the loft is no longer centered.

Sorry the audio is bad and the menus are missing. 

Although you can tell me how to make it so it's centered, I've already found ways to do that! For example, if I project the box and make my loft point based on the projected rectangle from the base, that linkage holds and it all does what I want.

My question is: why doesn't the projected point stay linked to the point I projected from? What do I not understand about Fusion?

Thanks for any tips!

[davebYYPCU]

I can't reproduce that.  You need this tick.

As you are in a new file, why not a Centre Rectangle?  

Using the centre rectangle means the projected point does not have to be made.

I'll call it a quirk of the system, a new sketch on orthographic planes projects the origin into the new sketch automatically.  In your case you now have a sketch, drawn nothing into it, and your model is always keeping the top point in the centre of the bottom profile.

Using the 2 point rectangle, your diagonal midpoint, project the point to a second sketch.  Updates as expected here.

Just as Screencast works here too, (Windows 10) so 

Cant help further, can you break my file?

[laughingcreek]

Yeah, once I saw the video I understood immediately what was happening.  This is a quirk (or a bug) of how fusion handles plane and sketch creation.  you thought you where selecting your projected point.  but the origin of the sketch was there first, and that is what you selected.  The "quirk" is that once a sketch is created on an offset plane, it's origin doesn't change, even if the underlying geometry that was used for the offset plane reference changes.  You can see in my screen cast (my turn to be shamed, I don't even HAVE a microphone) that I long mouse click the point and select the second point on the list, which is the point that was projected.

How did I know this? reading these forums.  now you know.  The logic of why the origin doesn't move has been explained before by someone from AD before, but I forget.

link to screen cast-

.sketch origin doesn't move 

[davebYYPCU]

Yeah, but that only happens when you select the body face to make the plane. 

Offsetting the origin planes has a higher recommendation, and I sometimes forget, what I take for granted.  His screen cast does tell you clearly what he selects for the plane to be offset from, certainly that's the why... and it wont show up in my file, as I bypassed the box for demo purposes.  Bonus is there was no opportunity to fall into that trap.