Stretch simple line with object at midpoint; dynamic block

[townest]

I want to create block thats a simple stretchable line with an object (say a circle) stuck at the midpoint no matter where the grips stretched to.  The circle would not scale, but would move/stick to the midpoint.   The line could be stretched to a rotated position.  

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Preferable with stretchable grips at both ends of the line, but just one side would work to.  Any pointers would be helpful.  Thank you.  Tyler  

[Libbya]

Add a linear parameter so its endpoints are at each end of the line.  Add a stretch action to each end of the parameter, place the stretch window around each respective endpoint of the line, and include the line in the selection set of each.  Add another stretch action to each end of the line, put the stretch window around the circle, add the circle to each selection set.  Select both stretch actions, go to properties and change the distance modifier to 0.5.  Done.  

[townest]

Thanks.  Almost there, but I need it to be able to stretch to a rotated position also, or stretch and rotate.

[j.palmeL29YX]

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@townest wrote:

   The line could be stretched to a rotated position.  

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I'd use a Polar parameter and a Polar Stretch action.

[Libbya]

Use a polar parameter instead of a linear parameter.  Use stretch actions, *not* polar stretch.

[townest]

Okay.  I got it working with polar parameter and stretch action on the line and polar stretch on the circle.  Since circle was just an example I need it to rotate also.  Imagine it's a triangle instead that needs to rotate.  

Final question.  What should I do with the basepoint.  It seems like eventually it will become rather disconnected with the block.  Is there a way to affix it to the midpoint, or center of circle/triangle?

Thank you,

Tyler

[Libbya · Accepted solution]

Add a basepoint parameter to the 0,0 point in the block (as a general rule that is the only place to put one) and adjust the block as necessary to accommodate that location.  You can move the base point parameter directly with actions, but there are a couple glitches that can occur especially if the block contains chained parameters.  Instead of moving the base point directly, it is better to add a chained point parameter, add a move to that chained point and move the base point parameter with the move action.  Any other actions you want to affect the base point parameter position should have the point parameter added to their selection set and *not* the base point parameter.

[townest]

Thanks @Libbya .  I got lost in the chained point but since my block doesn't have any chained parameters I went with your first solution.  I'll have to dig deeper if the need arises.