..and I always thought it meant, you're getting warmer?
The sketch origin is useful for two things:
- So you easily know where the 0,0 point of the sketch is, especially in the case where you are not on a plane that intersects the global origin (see Kelvin's reply).
- So you know which direction is horizontal (short arrow on the origin) and vertical (long arrow) for sketch relationships.
In most cases, the sketch origin is projected directly off of the global original of the part/assembly so the centerpoint of the sketch origin is the same as the centerpoint of the global origin when looking normal to the sketch plane. However, the short and long arrows of the sketch origin are only directly aligned with the global origin arrows if you are sketching on planes parallel to the front view. So the sketch origin is almost always useful for the vertical/horizontal orientation reference.
Also, the sketch origin does not always lie in a position projected from the global orientation. There are several commands that can move and rotate the sketch origin (and geometry in the sketch) such as:
In these cases, it is especially important to understand the sketch coordinate system since the sketch origin point and horizontal and vertical may not be aligned to the the global coordinate system at all.
I hope this helps,
I half agree with you - the red sketch origin is not always selectable. If you have the blue global origin hidden, then you cannot select the red origin to dimension to nor to attach a relation to.
With the blue global origin visible but with the model oriented so that you're not viewing normal to the sketch plane, then you get the same result: you cannot select the red origin to dimension to nor to attach a relation to. See pic 1. The dimension shown is between the global origin and the line but is displayed as if were connected to the sketch origin.
As Kevin indicated, you CAN attach geometry to the sketch origin. See pic 2.
Why can geometry attach to the sketch origin but not dimensions nor relations?
I thought this was a bug. I thought the sketch origin was always selectable. But I found this in SWx 2015, 2016, 2017.
It would be nice to have the red sketch origin always selectable.
If you can't select the red origin, sometimes you need to turn the model, I think SW gets confused at times, especially since there are so many automatic selecting tools used, so when you try to get the red origin, maybe SW thinks you would like to select a surface, or did you try and select the point of origin in the feature tree, see where that pops up.....
Yes, I failed to point that out .... that you can always revert to picking the origin in the feature manager. You get the same results that I show in pic 1 of my previous post.
In my (albeit, limited) experience you can always select the part/assembly origin if you expand the tree in the screen or select it from the history window.