Line Angle plane: angle to what?

laird_broadfield

The implication in the help for Plane (https://cad.onshape.com/help/index.htm#cshid=cplane) is that the angle is to the plane that hosts the line.  My experiments, however, suggest that the angle is to the global system.

Here's my experiment:


I put a line on the Top plane, a plane at 30 deg to that, a second line, and a line at 60 deg to that.  What I want is to specify that "plane on second line" is at X degrees from the plane that hosts Second Line, so that if I adjust the first plane, the change follows.  What I'm getting is that plane on second line is at X degrees from global flat.

How can I get what I want... or how am I conceptualizing this wrong?

(Experiment at https://cad.onshape.com/documents/27349a7d22794a6a993806f6/w/744e07fcdbd144cdace550d7/e/c3147f1d0e1e439b89174b52 if anybody wants it.)

andrew_troup

Bug or feature, it's well short of Onshape-quality, to my way of thinking

andrew_troup

I entirely agree with you, @laird_broadfield : to my mind, this is a serious deficiency, one of several in the current implementation of planes in Onshape.

I've previously raised this under "Feedback" with the folks at Onshape Support, and I suggest others do the same if it affects them.

It's a major stumbling block for me, since the current lack of 3D sketch capability makes planes indispensable in models which would otherwise not require them.

I think that the default reference plane for the angle should be the plane on which the sketch line lies (as you suggest), but ideally it should alternatively be possible, using the same tool, to select an arbitrary plane or face as the ref or datum plane, and/or use a linear (solid) edge rather than a line.

For me, this is the most commonly used plane creation tool, and it needs to work as well as possible.

I would personally prefer the default angle (measured from the sketch or reference/datum plane as above), to be 90 degrees for a newly created plane (rather than, as in Solidworks, the last angle used), but this is a minor consideration.

laird_broadfield

@andrew_troup: Oh, good -- given that I'm largely self-educating my way into this, I tend to assume that I'm thinking incorrectly, rather than finding genuine issues or shortcomings.

Given that the Create Plane object selector already accepts multiple selections, one could just add both the line and the line's host plane as a way to specify the preferred reference without losing backwards compatibility.  (Indeed, in the midst of typing my note, I thought of that and went back to check if that was the method, because it seemed so obvious once I'd thought of it.)

shanshan

I think if we creat a plane by "line angle",it is not a steady plane.now let me try !
step1: creat sketch 1, draw a line on the front plane ,and give the value 60 degree for the angle between this line and X axis.
step2: creat plane 1 with this line and give 0 degree for angle value by "line angle".
step3: reedit sketch 1,change the angle from 60 degree to 30 degree
step4: we can see the vector of plane 1 will rotate 90 degree.

_Ðave_

I was a bit frustrated trying to anticipate the direction that a plane would take with the plane/angle option. Had to continually experiment to get want I wanted. @shanshan Glad you identified this apparent bug. 

3dcad

@lougallo @jakeramsleyI would like to see some comment of Ons people for this plane issue.

I would really like to set also angles when creating a plane in offset to another plane. I don't like to create sketch for driving a simple say 45 deg to normal plane.

traveler_hauptman

The line-angle plane angle problem has to be a bug.....

jakeramsley

3dcad said:

@lougallo @jakeramsleyI would like to see some comment of Ons people for this plane issue.

I would really like to set also angles when creating a plane in offset to another plane. I don't like to create sketch for driving a simple say 45 deg to normal plane.

Looking at the code, it isn't random but not easy to predict what the 0 degree plane is.  We are essentially looking for what the dominant unit vector is of the line, be it [1, 0, 0], [0, 1, 0] and [0, 0, 1] and get the cross of that for the normal of the plane.  From here, we start rotating about the line with a right hand rule (I believe).

andrew_troup

Bug or feature, it's well short of Onshape-quality, to my way of thinking

traveler_hauptman

@jakeramsley Thanks for sharing that. It makes a whole lot more sense now. It's a natural way to attack the unknowns global angles create. Not a bug, just coding the wrong feature.

If it's not clear from the above comments... We want local angles.

With local angles it's easy to create the effect of global angles using the core reference planes. With global angles it's not easy to create the effect of local angles.

robert_uhrik

still after 9 years this is wrong in onshape... so big shame...

_anton

While I used to use planes a lot, I've converted almost exclusively to mate connectors now. They're far more useful. These days, I only make a plane if I need to put one through three points.

NeilCooke

robert_uhrik said:

still after 9 years this is wrong in onshape... so big shame...

Select a second reference to define the angle parametrically.