Adjust arc with fixed radius

[miguelmachadoecosta]

I am not being able to get an action to work as I wish. I have a block (attached) with three line segments and two fixed radius arcs connecting their ends.

I want to be able to rotate the extremity segments and adjust the arc accordingly. I tried two different approaches (one in each extremity) but each has it's faults.

The first approach consisted of rotating the left segment illustrated in the following image about the point of intersection of the red lines. Graphically it works but the problem is that when I also rotate the parameter that measures the distance from the extremity to the point of intersection of the segments the distance gets wrong because I am not able to stretch it.

For the second approach I did the rotation about the point of intersection of the blue lines. In this case the distance parameters are alright but radius of the arc is changing. I tried to constrain it's radius but in that case I cannot get its center to move.

The mechanism I need is the one illustrated in the figure. The rotation is about the intersection of the blue lines, the arc's radius remains unchanged and its center moves, as well as the end of the horizontal segment. Is it possible to achieve this?

As secondary less important problems I am having with this block: (i) when I stretch horizontally the middle upper text isn't moving, unlike the other texts, and (ii) when I flip the arcs are getting the opposite curvature of what they should.

Thank you in advance.

[MetalFingerz]

Hi Miguel,

I can't really help with your arc issues as I'm not good enough with parametric constraints an also because I'm not sure about what you want to do.

However I can help with your secondary issues :

 - Your attribute doesn't move with the stretch actions because it is not in locked position. When editing your block, in its properties, put "lock position" on yes, then attsync it. Create a move action with a 0.5 distance multiplier, include the attribute and that will work.The "lock position" is for the attribute not to be moved independently.

 - The flip action acts that way because of the coincident constraints. As the arc and the lines must be tangent and coincident, as you designed it, your left arc has to curve "to its right" (from the center of your block) and the right one to its left. When flipped, the arc can't curve as constrained and has to do that weird curve which is it most likely it creating a tangent to the direction is has to go when the lines aren't aligned at 180°.

[miguelmachadoecosta]

Thank you very much. You've been very helpful.

For the arc problem I didn't find the solution I was looking for, but I found an alternative that seems to fit my purposes. Since the rotation about the center was the arc was working well except for the distance dimension, I replaced that dimension with an attribute that measures a straight line lenght. Your answer now helped me moving that new attribute.