@jeff_strater wrote:
I have been following this thread very intently. Some amazing sketch-free models here. The part of the thread that is most interesting to me is the "parametricity" (not a word, but it should be!) of the models, or lack thereof. Since a lot of these sketch-free models rely on solid primitives, the core of the "is it parametric" question comes from the fact that you cannot accurately constrain the sketches that are used to build Box, Cylinder, Torus. So, if you alter the face that, say, a Cylinder was placed on, there is nothing that will keep it "in the right place" after the update.
Ironically, the solution that has been discussed within the team is: ... Keep the sketch around! We use sketch tools to place the initial geometry. You can tell that from the UI. But, to keep primitives simple, once the primitive is created, we discard the sketch, so it does not complicate the timeline, etc. The goal was to keep Primitives primitive. But, the loss of editability (you cannot change the plane a Primitive is placed on, for instance, or change the origin position of a Cylinder, and parametric nature of the Primitives means they are less useful.
So, I am interested, for those that claim these designs are fully parametric, how you were able to achieve that. Or, is it just a question of "what kind of parametrics?"? And also, going forward, where should we go with Primitives? Make them more parametric (meaning, probably, keeping the sketch and allowing it to be edited), or keep their current "sketch-free" (kind of) nature?
Jeff
And this is the very essence of the issue. What is the most efficient (minimum information input) way to fully define/constrain a 3D model? Sketches do work well no doubt, but I think what makes primitives attractive is that the sketches are discarded and therefore don't clutter up the timeline and the design tree. If the sketches are kept, then there is no benefit to using primitives as opposed to standard sketch and extrude. So how to add parametric position control? I would envision what is basically a 3D version of the existing sketch dimensioning and constraint system. Interestingly what you would end up with is almost exactly how the Solidworks mate system works for assembling parts at the assembly level. Fusion (not being Solidworks) would probably want to instead do something like the joint system used for components (or possibly the new move command?), except make it work for body primitives, which can then be later *combined* to form a single body. Now ironically, If such a system were implemented, it would not simplify the timeline at all because instead of sketches we would have positioning commands.
Therefore, whatever the mechanism is to add parametric control to primitives, would need to be done in such as way as to be contained within the primitive command itself, much like the hole command. Hopefully this parametric control would also include some basic geometric constraints (coincident, midpoint, etc.) as well as dimensioning.
C|
