3D sketch is incredibly buggy and dumb

[dabra015]

What can I do to prevent Fusion from being incredibly dumb when it comes to using constraints and dimensions in 3D sketch? I get that it's a complicated thing for a program to move things around like this in 3D space and calculate where all the points even can be, but when we're talking about a line that's fixed in place and one like that's free to move wherever it wants, and trying to restrict the angle makes the damned program break, then there's clearly something wrong. This isn't the only dumb thing Fusion does. I can have two lines on a plane and try to combine the tips with the Coincident constraint and it just goes "Nah. That's not possible" when I can literally drag the points together manually..

(You can probably tell from my language that I'm incredibly frustrated after working for 3+ hours with repeated dumb error message after dumb and just flat out wrong error message)

I know I could have just made this simple design using extrusions, 2D sketches and other solutions, but I wanted to do it all in one go. So, is there a better way of treating 3D sketch, what are the limitations, some bad and good habits and so on?

[davebYYPCU · Accepted solution]

I know I could have just made this simple design using extrusions, 2D sketches and other solutions,

Design Differently is a marketing slogan, not an instruction.

but I wanted to do it all in one go. So, is there a better way of treating 3D sketch

Nope.  Excellent demo of the reason we don’t use them.  (Dimensions and constraints are unreliable.)

Might help…

[dabra015]

Dang. It's clear it doesn't have to be that way though, ideally. Like you said, excellent demo that fusion's algorithm isn't perfect, although I have no idea what the perfect algorithm would be.

Followup question though. If dimensions and constraints are unreliable, what other options are there? What is the most reliable way to model such that if you change parameters that were set early in the history, you'd rather consistently get the expected model out the end? I hope you have a more reliable solution and that when you said unreliable you meant compared to something else.

[davebYYPCU]

If changing parameters with blue articles, you are in for the next nightmare.

Fully constrained 2d sketches and modelling tools using those sketches, works for me.

Might help…..

[TrippyLighting]

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@davebYYPCU wrote:

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Fully constrained 2d sketches and modelling tools using those sketches, works for me.

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Have worked for me as well for the last 25 years with parametric 3D CAD.

3D sketches have their purpose for some surface designs and perhaps frame and piping design.

[dabra015]

"Blue articles"? Like, undefined lines and such? If so, yeah, that totally makes sense, since it seems Fusion is pretty selective with what it grants "black", but I guess a line is blue and locked in place because there could be another valid spot for it to be, just not somewhere you can drag it, and "black" means fusion knows for sure where it's supposed to be. Is this what you meant?

[davebYYPCU]

Black denotes fully constrained, a red pin on the sketch label denotes all sketch articles in it are effectively black (purple or green).

Blue, Orange lines and White points - Fusion sees as still able to move from here.  Add Change parameters involving undefined articles that have no anchor to work from - generates the nightmare.

I guess a line is blue and locked in place…. - is not possible.

Might help….

[dabra015]

I've had blue lines that are "locked in place" as in I can't drag them around, and the constraints logically show that moving them should be impossible, but I'm guessing they were in a bi-stable state, where it had multiple possible immovable and stable places, which isn't "locked" locket. Just a finite amount of stuck locations rather than an "infinite" gradient letting me drag them. Anyway, thank you both so much for your help. I appreciate it tons