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Thread: Any ideas how to build this family (scalene triangle formulas)

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    Any ideas how to build this family (scalene triangle formulas)

    I'm struggling here for some time now, and started to loose the hope this is actually possible in Revit.

    Basically I'm trying to build the family, 2 folding arms, one shorter than another. I want it to automatically change all the angles when the total length of the component changes. Because I have the arm lengths as the only given, fixed data, I can't figure out how to make it work. Any ideas how to resolve it, or maybe any of you seen similar Revit family done so I can have a look?

    https://snag.gy/IYSR7p.jpg

    I tried to use the percentage value (if 340 is 100%, then 200 is x%), but for some reason it doesn't come out accurate, so I'm totally lost

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    Forum Co-Founder Twiceroadsfool's Avatar
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    Its possible in Revit.

    All you need to do is make angle constraints, on reference lines. Then make parameters that calculate the angles based on the three lengths given (you have three pieces of information given: Total length, and length of each arm).
    cganiere likes this.

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    Quote Originally Posted by paidpal View Post
    I'm struggling here for some time now, and started to loose the hope this is actually possible in Revit.

    Basically I'm trying to build the family, 2 folding arms, one shorter than another. I want it to automatically change all the angles when the total length of the component changes. Because I have the arm lengths as the only given, fixed data, I can't figure out how to make it work. Any ideas how to resolve it, or maybe any of you seen similar Revit family done so I can have a look?

    https://snag.gy/IYSR7p.jpg

    I tried to use the percentage value (if 340 is 100%, then 200 is x%), but for some reason it doesn't come out accurate, so I'm totally lost
    will take some trig I think. The problem that I see is that there are more variables to the equation than you have presented. The angle of each "arm" can be anything between 0 and 90 and each can be different. So you could vary the angles at one side or the other or both to get your width result. How do it know? (old joke punch line, sorry). I'm sure that some of the more math intelligent people around here will steer you in the correct direction.

    Edit: see, I was 1 minute late

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    Quote Originally Posted by Twiceroadsfool View Post
    Its possible in Revit.

    All you need to do is make angle constraints, on reference lines. Then make parameters that calculate the angles based on the three lengths given (you have three pieces of information given: Total length, and length of each arm).
    It would be super nice if you could provide some simple example, as I have tried everything I could come up with and still couldn't achieve desired result.

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    Last edited by cellophane; December 28th, 2016 at 07:21 PM.

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    Forum Co-Founder Twiceroadsfool's Avatar
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    Three parameters, with 2 reference lines. Dont even need the trig, to make the simple rig that moves and flexes when the overall length (L_Main) is changed.

    FWIW i would still build the trig in, and constrain them with Angles, if it were me. But this method works, and took about 2 minutes to do.
    Attached Thumbnails Attached Thumbnails Any ideas how to build this family (scalene triangle formulas)-2016-12-28_13-41-29-sample-simple-2.png   Any ideas how to build this family (scalene triangle formulas)-2016-12-28_13-40-55-sample-simple.png  

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    As Aaron says, here it is... You can change the dimensions of each arm as you wish. If you move the refence plane on one side, the whole thing will adapt and change its angles.
    Attached Files Attached Files

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    Moderator cellophane's Avatar
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    I made one a while back that allows the adjustment of any side's length that seems to work fine. I actually didn't need any reference lines either...
    Attached Files Attached Files

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