Face relative coordinates for a sketch

marena_richardson

I have a feature script feature where the user has selected a face, such as one side of a cube. I want to draw a sketch on that face. I can draw a sketch on that face but it still originates from world coordinates. How can I make the center of my sketch the center of the face I am drawing on? 

marena_richardson

I tried evFaceTangentPlane by the way which will make a new origin but returns a plane, not a query, which the sketch will not accept as an input for "face". 

ilya_baran

newSketchOnPlane (instead of newSketch) will accept a Plane as a sketchPlane and won't recenter it.  If your face is planar, you can also use evPlane to get the plane centered on the face middle instead of evFaceTangentPlane.

marena_richardson

Thanks Ilya. newSketchOnPlane and evPlane both work well. What I am struggling with now is how to make a sketch appear the same on all faces despite their different orientations relative to the global coordinate system. 

ilya_baran

Not sure what you mean by "the same" -- evPlane returns planes in a "canonical" orientation, but if you rotate them, newSketchOnPlane will use what you give it.  If you are referencing geometry outside the sketch (unlikely but...) and simply using a different plane wouldn't work, keep in mind that you can also use opTransform and opPattern with qCreatedBy(id + "sketch", EntityType.BODY)

marena_richardson

Hm. I wasn't very clear. What I really need is a sketch on one face that appears mirrored on another face so that the two sketches would line up if the bodies were moved into contact. 

kevin_o_toole_1

Note that if the rotation of the plane returned by evPlane is arbitrary. You can specify a plane with a different rotation like:

newPlane = plane(oldPlane.origin, oldPlane.normal, newXDirection);

lana

@marena_richardson
Planes have right-handed coordinate systems, so you can't get symmetric sketch by manipulating sketch planes only. If the faces are in the same plane, you can use MIRROR constraint in the same sketch. You probably will be using sketches to make extrude. It might be easier to build the body you are looking to build and then mirror and transform it.

ilya_baran

@lana
I think it's easier to just have the sketch normal point opposite the face normal -- the default extrude direction will be wrong, but that doesn't seem like a big deal. The other possibility, like I said above, is using opTransform or opPattern on the sketch itself, which can take transforms with negative determinant.