opMoveFace distance & direction?

MichaelPascoe · October 2020

I'm trying to move a face 1" in the direction of the zAxis of the csys that I created. What I have now moves it 1" from the world origin... How do I do this?

opMoveFace(context, id + "moveFace1", {
                    "moveFaces" : faceToMove[5],
                    "transform" : transform(-toWorld(selectedCoordinateSystem, vector(0, 0, 1) * inch))
                });

Jake_Rosenfeld · October 2020

@MichaelPascoe

You could just use this overload of `transform`:
https://cad.onshape.com/FsDoc/library.html#transform-Vector

which takes a translation vector. Then your transform would just be:

transform(zAxis(selectedCoordinateSystem) * (1 * inch))

When passing a transformation into interfaces like this, it is helpful to keep in mind that what is happening is:
eachResultPoint = givenTransformation * eachPointOnTheInputGeometry
the key here being that the input points are multiplied on the right of each transform (which can be thought of as a matrix). So if you give multiple transforms, it is:
eachResultPoint = xformA * xformB * xformC * eachPointOnTheGeometry

With this in mind an appropriate way to do the transformation that you want, but for any arbitrary translation in the selected coordinate system, would be:

const selectedCSys = ... your coordinate system
const translationInSelectedCSys = ... a translation that you want to occur, in the reference frame of `selectedCSys`

const xform = toWorld(selectedCSys) * transform(translationInSelectedCSys) * fromWorld(selectedCSys);

opMoveFace(..., {..., "transform" : xform});

What this transform does (reading right-to-left as described above), is take each point on the desired face, apply a fromWorld to change the point from world space coordinates to selectedCSys coordinates, apply the desired translation, then apply a toWorld to change the point from selectedCSys coordinates back to world space coordinates.

Let me know if you have additional questions.

Jake_Rosenfeld · October 2020

@MichaelPascoe

You could just use this overload of `transform`:
https://cad.onshape.com/FsDoc/library.html#transform-Vector

which takes a translation vector. Then your transform would just be:

transform(zAxis(selectedCoordinateSystem) * (1 * inch))

When passing a transformation into interfaces like this, it is helpful to keep in mind that what is happening is:
eachResultPoint = givenTransformation * eachPointOnTheInputGeometry
the key here being that the input points are multiplied on the right of each transform (which can be thought of as a matrix). So if you give multiple transforms, it is:
eachResultPoint = xformA * xformB * xformC * eachPointOnTheGeometry

With this in mind an appropriate way to do the transformation that you want, but for any arbitrary translation in the selected coordinate system, would be:

const selectedCSys = ... your coordinate system
const translationInSelectedCSys = ... a translation that you want to occur, in the reference frame of `selectedCSys`

const xform = toWorld(selectedCSys) * transform(translationInSelectedCSys) * fromWorld(selectedCSys);

opMoveFace(..., {..., "transform" : xform});

What this transform does (reading right-to-left as described above), is take each point on the desired face, apply a fromWorld to change the point from world space coordinates to selectedCSys coordinates, apply the desired translation, then apply a toWorld to change the point from selectedCSys coordinates back to world space coordinates.

Let me know if you have additional questions.

MichaelPascoe · October 2020

Thank you Jake for the quick response! I will give this a try.

opMoveFace distance & direction?

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