Problem while creating parametric truss design using surface pattern

[dkevin77]

Hello everyone. I wanted to ask whether someone could tell me what is wrong with my design and how to fix it (as it does not behave appropriately I guess). 

The first picture is the revit family file in which I have loaded it in to the project (metric mass) file (second picture). I created a parametric surface using the create form features, and it gives the grid perfectly until I switched the pattern to the revit family file like the first picture. 

It looks like the family member does not adapt accordingly to the surface pattern, and still leaves a lot of spaces between the points. The correct version (the one that I am expecting to have) is supposed to be like the third picture.

Really hope someone could help me. I am quite new to Revit and these exercises are based on youtube tutorial videos... As for the template, I used the Metric Generic Pattern Based for creating the revit family member, and Metric Mass for creating the Parametric Truss Form. Any opinions would be highly appreciated. Thanks a lot!!

My Revit Version: Revit 2020.

 

  

[barthbradley]

Post the file.  

[dkevin77]

Here you go. Attached is the family member (named "Truss Family") and the parametric truss design (named "Parametric Truss System"). Many thanks!

[barthbradley · Accepted solution]

Is this what you are after?

Open the "Truss Family bb" in the attached RFA and examine how I did it. Note Parameters "H", "Radius", "R" and "RR". 

[barthbradley]

... you don't mean you want the trusses to overlap like this?: 

If this is what you want, then delete the formula for "R" in my family, and then enter zero ("0") for the "R" value.  But obviously, that's not the way the truss will be constructed in the real world.  Two masses can't occupy the same space. 

[bin]

Maybe think about how this is going to be constructed? 

Maybe model the truss as a single element? Something like this?

[dkevin77]

Oh yes!! Thanks so much for it. Your attached file is the one that I am looking for (i.e. the circumference of the parametric system is connected smoothly by the upper square cylinders of the family). As for the parameters, I am not quite clear what do R and RR refer to. I understand you use "Radius" as a reporting parameter in which "R" would have a value of 3/2*R and "RR" = -R. I tried to change the value of the parameter; however sometimes the results reported an error about the constraints between the members, hence it is quite difficult for me to know what range of "Radius" so that R and RR could have a reasonable and appropriate value.

And may I look on the family file of your "Truss Family bb"? I am still not quite clear about how yours could bring the correct pattern on the divided surface, which is not the case for me. What is the issue on my original truss family file? Does it have something to do with constraints? 

[dkevin77]

Hello! I tried to create what you have recommended to me and end up with this result. The left one was the family file created by @barthbradley, which is the one I am expected to have. As you can see, all the "upper square" or "prism base" are all connected to each other and adapt to the surface curve. However, when I tried to use my own family file (the right one), it seems like they wont connect and enclose smoothly on the circumference. Any ideas what is wrong with my family file? I originally did not include any parameters to control my family (yeah, my big mistake), but I believe there is something I am missing out here.

[barthbradley]

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@dkevin77 wrote:

may I look on the family file of your "Truss Family bb"?

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It's in the family I posted. Didn't you open it?  I think you opened the wrong one, but both are the same as I recall.  Just a hiccup.  Check and see if there's a difference.  

Also, use XRAY Mode to examine the family. Select the Reference Points and look at there Offset Parameters to see what Family Parameters control them. You should be able to figure it out from examining those associations and by flexing the Family.  

[barthbradley]

It's all about hosting Ref. Points to other Ref. Points.  

https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2015/EN...

[dkevin77]

Isn't the one you attached is the mass file? I was asking about the generic pattern based file (the one in which you create the individual part). Still not sure about what is wrong though, I checked my generic pattern based file again and it seems that everything is fine. The top element (inverted prism base) is a square, but somehow when I load it into the mass file, it got distorted (not a square anymore, more like a trapezium). 

  

[dkevin77]

I see. Let me try and see whether I could spot something. Thanks a lot

[barthbradley]

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@dkevin77 wrote:

  

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You opened the wrong family. I did forget to associate one of the Ref. Points in one iteration.  That would explain this deformity.  

[bin · Accepted solution]

If you open your truss family, flex your family by changing the pattern size. You will find that point 3 and 4 is not moving properly. 

Simply create them again using the work plane of Adaptive Point 3 and 4 will fix everything.

To avoid the stacking framing, simply create the member 1 and 2 as separate elements and give them instance visibility parameter with default unchecked setting. After loading it into your mass, select the edge ones and turn them on accordingly.

The final result will be something like this:

[dkevin77]

Hi Bin, thank you so much for the reply. I have followed your steps to create separate elements on member 1 and 2, and put an instance parameter on it. However, I was still not being able to achieve the final result you have attached. Here is the screenshot of where I am now.  

I am not quite sure what did you mean by "select the edge ones and turn them on accordingly." What do you mean by "select the edge ones"? I have tried to re-turn on the Side1 and Side2 parameters, and I ended up to no avail. As you can see on my first picture, Side1 and Side2 members are not featured on the circumference. 

Attached is the Revit file I have progressed on.

Really appreciate if you could tell me what I am missing on. Thanks so much!

[bin]

First, flex your family. You will find there is still 1 point not following the adaptive point.

After you fix this point, load it back.

Then use your Tab key to select the single family on the edge, and check those options.

[dkevin77]

Really grateful for your thorough guidance! I finally could achieve a more proper one. Although I still see on some part of the edges are not arranged smoothly, I think it is pretty adequate already.

 Thank you so much!

[dkevin77]

Hi again! I think I understand my mistake now. On the file you have attached, the outer square circumference corresponds to the adaptive points, whilst for my case, the centre point of the circle (which I used to create the cylinders) was the one aligned to the adaptive points. Hence mine has so many overlapping members, which obstruct the final result. 

Really thankful for your effort in providing me the corrected file. Thanks so much