I can add a few more details here, especially around the "not always" part.
As Bob says, those "dots" are the endpoints of sketch curves (and other sketch points - arc centers, even points added by themselves). And the purple geometry indicates that the sketch curve has been projected from other geometry in the model (either by sketching on a face, or specifically using the Project command).
So, there are two aspects that determine the "not always" part - Fusion only draws the dots in certain cases, for user-created geometry:
- standalone points
- arc or circle centers
Second, for projected geometry, Fusion does show the endpoints more often, for instance if you project a face into a sketch:
There is one relatively new behavior, though, that can cause some confusion: When you sketch on a face, Fusion does not automatically show the projected geometry from this face. The reasons why this is done is to reduce clutter in the sketch. Those curves are there, but just not shown. But, when you "use" one of those hidden curves, Fusion will draw it. For instance:
So this can cause some head-scratching, because these purple lines and points can "appear" sometimes without obvious reason.
Hope this helps clear up some of the questions about this area.
Jeff
Jeff Strater
Engineering Director