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## Strand/curve roll - similiar to bending

22 REPLIES 22
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Message 1 of 23
1768 Views, 22 Replies

## Strand/curve roll - similiar to bending

Hi!

Anyone tried to implement curve roll/unrolling?

It is similiar to per axis bending, but you execute the rotation on a per point basis relative to the previous point as a pivot. More description here: https://www.tokeru.com/cgwiki/index.php?title=CurveUnrollTutorial

I tried to implement the vex code presented on the page, but gave up after couple of hours...

Thanks

Dan

22 REPLIES 22
Message 2 of 23
in reply to: kmdaniel

Imo it would be easier to re-apply the logic rather than trying to convert the VEX code 1 to 1.

You'd need to an iterate loop compound. current_index start at i=1. Subtract all the points i=2 to i=n from the previous point position (i=1), so that the rotation can be applied locally, rotate these points around the binormal at i=2, add the previous point position back to move the rotated points back to world space, re-set these points inside the array. Repeat the process at i=3 to i=n... subtract from i=2....etc. Until the end of the strands.

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
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Message 3 of 23
in reply to: mjcg91

I managed to do this. Here is the maya scene if anyone interested:

Video:

https://drive.google.com/file/d/1WD3qwBubb-2psz4ZUztKwaPJOTwxfN1s/view?usp=sharing

Sadly, doing this one strand versus doing it on multiple strands is way more complicated to figure it out than I thought. It is really frustrating to handle the curve-offsets, and handle all that jazz, although I just want to do the same per strands. But it is there, the per strand version and the version for multiple strands.

Message 4 of 23
in reply to: kmdaniel

Nice! Your implementation works great but I see some unnecessary steps which might cost a lot of performance. You could put the implementation into a for-each compound, slice the necessary data (position, binormal, ratio...) for each strands, and then process it into an iterate loop. output from the for-each, flatten the new position array and finally re-save the geo property.

I gave it a quick try yesterday. I didn't use the angle calculus from the vex code but tried something different. I attached a wip scene file using a straight curve. You could take a look at the implementation and use the same fashion to implement your roll algorithm. I believe it's going to run much faster this way.

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
https://discord.gg/bifrost-addicts
Message 5 of 23
in reply to: mjcg91

You can try this compound.

Message 6 of 23
in reply to: morten.bojsen-hansen

@morten.bojsen-hansen  Wow that's amazing!

Your implementation is so clever. Updating the prev_point_orient at each iteration is far more efficient than what I had in mind to do this. Thanks for sharing !!

Maxime Jeanmougin - Technical Artist
https://maximejeanmougin.com

Join the Bifrost Addicts community on Discord:
https://discord.gg/bifrost-addicts
Message 7 of 23
in reply to: morten.bojsen-hansen

Cool thanks!

Message 8 of 23
in reply to: morten.bojsen-hansen

Morten, could you show me how to isolate the "rolling" functionality from this? Where I can set the angle, curve ratio (start of curvedness) ?

Message 9 of 23
in reply to: kmdaniel

You can control the angle by changing either the spatial_distance or curl_speed on the compound (unfortunately, the compound is not resolution independent - oh well). The actual "code" for this is in for_each2 inside. It's using the same exponential formula that everyone else seems to be using. 🙂

Message 10 of 23
in reply to: morten.bojsen-hansen

I downloaded both the example files, roll_strands and roll_strands_01. Jason file is inside the compound folder and I can bring it in to graph. But when I open the roll_strands_01, how do I complete graph? Help is much appreciated.

Message 11 of 23
in reply to: kmdaniel

I love people shares stuff that seem easy for you, but not for all. Thanks

Message 12 of 23
in reply to: morten.bojsen-hansen

I've encountered in a problem. Using roll strands compound. i slide the value accidentally to negative for the spatial distance and maya is calculating. No esc option works so after some minutes it close without error.

So how to set a value were i don't want accidentally go negative or a very little value?.A limit for value entry?

Thanks

Message 13 of 23
in reply to: darioOrtisi

@darioOrtisi To set a limit on a value:

• make the roll_strands compound editable
• click on the "pencil" icon to customize the UI
• click on the spatial distance parameter
• set the min field in the Customize UI dialog to 0
• Exit edit mode

Ian Hooper
UX Architect
Message 14 of 23
in reply to: ihooper

Thank you @ihooper

It's definitely been a long time since I've opened bifrost despite having upgraded it to latest version.

Thanks edit UI works really well.

Good job

Dario

Message 15 of 23
in reply to: kmdaniel

Just tried this, it works real nice, after I replaced some nodes.
The question is what would be the best way to resample strands, but not to lose the shape. If I add resampling, it shrinks the size.

Message 16 of 23
in reply to: mjcg91

Downloaded roll_strands_01.zip
and after loading maya has warned about some python script, in line 227 there is some vaccine.py.
Not sure what this is ?
Thanks.

Message 17 of 23
in reply to: kmdaniel

@stigla If Maxime's compound doesn't work for you, you could always try mine https://area.autodesk.com/m/morten-bojsen-hansen/assets/usermortenbhroll-strands

Message 18 of 23
in reply to: morten.bojsen-hansen

Hi,

I was trying to rebuild the adv version, like in your tutorial
https://www.youtube.com/watch?v=7X1rgzVU6E8
but got totaly stuck.
Could you share the advanced version or the link you've sent is the one just not called that ?

Thanks

Al

Message 19 of 23
in reply to: kmdaniel

@stigla That's not my tutorial, unfortunately, so you'll have to contact the author.

Message 20 of 23
in reply to: morten.bojsen-hansen
Sorry, my mistake.
Thank you for the script, I'm trying it, it will be fine.
Just a small question. I have svg file, what would be the best way to change curve/strand normalsto stay oriented to the screen, like 2D vector file.

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