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# coordinate system with one of its axes directed toward plate

Member Posts: 20 PRO
Hello,
I start my adventure with feature script and need some help.
I wanted to create coordinate system with one of its axes directed toward plate.
My input data are two plate edges - long edge and plate width.

Here is what I thought feature script should do:

1. get end points of plate width - point 1 and point 2
2. create plane that contains long edge and is perpendicular to plate width - checkPlane
3. check distance from point 1 and checkPlane
4. create vector - if point 1 lies on checkPlane vector should be from point1 to point 2 - otherwise vector should be from point2 to point1
5. then create coordinate system based on long edge origin, long edge direction and  previously created vector

Until step no 4 everthing works, but created vector always points in the same direction, no matter which edges I choose.

I would appreciate pointing my mistake and way of fixing it.

Here is script of point 4:

var gVector;
if (checkDistance==0)
{
gVector = normalize(gPoint1-gPoint2);

}
else
{
gVector = normalize(gPoint2 - gPoint1);

}

• Posts: 1,921
I haven't looked at your code, but you could assume that the thickness is always going to be less than the front face area, then use qEdgeAdjactent to find both faces then qLargest to get the front face then create a plane with a normal opposite to the face.
Neil Cooke, Director of Technical Marketing, Onshape Inc.
• Posts: 888
Hi,

I can see two possible issues:
First, checkDistance is a length, and 0 is a number.  They will never compare equal.  You can use 0 * meter instead.
Second, you should do a tolerant comparison in case checkDistance is not exactly zero because of floating point roundoff error.  The check I would use is something like:
``if (tolerantEquals(checkDistance, 0 * meter))``
Hope this helps.
Ilya Baran \ Director of FeatureScript \ Onshape Inc

• Moderator, Onshape Employees Posts: 1,921
I haven't looked at your code, but you could assume that the thickness is always going to be less than the front face area, then use qEdgeAdjactent to find both faces then qLargest to get the front face then create a plane with a normal opposite to the face.
Neil Cooke, Director of Technical Marketing, Onshape Inc.
• Member Posts: 20 PRO
Thank you very much @NeilCooke !
Your way works great and is so much shorter

Although for the sake of learning purposes I would love to know, why my way hasn't worked as expected. So it would be great if somebody has some free time and could explain it to me.
• Onshape Employees, Developers, HDM Posts: 888
Hi,

I can see two possible issues:
First, checkDistance is a length, and 0 is a number.  They will never compare equal.  You can use 0 * meter instead.
Second, you should do a tolerant comparison in case checkDistance is not exactly zero because of floating point roundoff error.  The check I would use is something like:
``if (tolerantEquals(checkDistance, 0 * meter))``
Hope this helps.
Ilya Baran \ Director of FeatureScript \ Onshape Inc
• Member Posts: 20 PRO
Yes, this helped a lot - writing  0 * meter solved my issue. Thank you for explanation