create mesh from strands? not extrude along strands

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anhungxadieu
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create mesh from strands? not extrude along strands

Post by anhungxadieu » 21 Jan 2016, 14:13

hi there,

i don't know i set this title correct or not so bare with me :ymblushing:
i want to ask a question: how can i create a mesh from the strands (this case is a grid mesh) ... like this image below, i know we already have one compound "extrude along strands" but my question i difference.

thank for your attention :)
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rray
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Re: create mesh from strands? not extrude along strands

Post by rray » 21 Jan 2016, 16:34

There's a Build Topo node that you can use, you give it a list of point positions, and a list of indices from that list of what points it should create the polygons (separated by -1's)
When you execute it, you get the mesh.

So for the positions you would do this:

Get empty polymesh->Create ICE tree
Get Strand Positions->Build Array from Set->Create Topo->Set Topology->ICETree

For the list of indices the goes into the Create Topo it gets more complicated

If your strands have n points you'll have to generate this array:

0, 1, n+1, n, -1, (<<--- this is the bottom right polgon in your image, ended with the -1)
1, 2, n+2, n+1, -1,
...
...
...
n-2,n-1, n+n-1, n+n-2, -1, (<--- end of polyong strip between first two strands)

n, n+1, 2n+1, 2n, -1, (<----- first polygon of second strip)
n+1, n+2, 2n+2, 2n+1, -1,
...
...
...
...

Not sure yet how to create this in ICE, maybe some modulo calculations combined with some of the array nodes

Maybe there's a simpler solution, too :-s
softimage resources section updated Feb 7 2019

anhungxadieu
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Re: create mesh from strands? not extrude along strands

Post by anhungxadieu » 21 Jan 2016, 17:12

rray wrote:There's a Build Topo node that you can use, you give it a list of point positions, and a list of indices from that list of what points it should create the polygons (separated by -1's)
When you execute it, you get the mesh.

So for the positions you would do this:

Get empty polymesh->Create ICE tree
Get Strand Positions->Build Array from Set->Create Topo->Set Topology->ICETree

For the list of indices the goes into the Create Topo it gets more complicated

If your strands have n points you'll have to generate this array:

0, 1, n+1, n, -1, (<<--- this is the bottom right polgon in your image, ended with the -1)
1, 2, n+2, n+1, -1,
...
...
...
n-2,n-1, n+n-1, n+n-2, -1, (<--- end of polyong strip between first two strands)

n, n+1, 2n+1, 2n, -1, (<----- first polygon of second strip)
n+1, n+2, 2n+2, 2n+1, -1,
...
...
...
...

Not sure yet how to create this in ICE, maybe some modulo calculations combined with some of the array nodes

Maybe there's a simpler solution, too :-s
hi,
i'm not sure i understand well but i will give a try
Thanks rray! :ymhug:

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rray
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Re: create mesh from strands? not extrude along strands

Post by rray » 21 Jan 2016, 23:54

Couldn't resist a try ... :ymblushing: her's how the index array could be constructed:

Image
softimage resources section updated Feb 7 2019

Bullit
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Re: create mesh from strands? not extrude along strands

Post by Bullit » 22 Jan 2016, 00:27

My give some ideas.


NNois
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Re: create mesh from strands? not extrude along strands

Post by NNois » 22 Jan 2016, 00:38

Couldn't resist too ! (the fact you need to keep moving on and xsi is dead)

That's how you do it in Houdini... one single node ;-)

Cheers
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anhungxadieu
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Re: create mesh from strands? not extrude along strands

Post by anhungxadieu » 22 Jan 2016, 02:05

hi,
it's interesting, i think it's possible to achieve a some effect like this one (a movie below, i think thing he create it in Houdini)

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FXDude
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Re: create mesh from strands? not extrude along strands

Post by FXDude » 22 Jan 2016, 03:20

Indeed everything possible with curves should have been (natively) possible with strands.

Yet this might be of help,



You should then be able to loft the (live) curves.

anhungxadieu
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Re: create mesh from strands? not extrude along strands

Post by anhungxadieu » 22 Jan 2016, 05:37

rray wrote:Couldn't resist a try ... :ymblushing: her's how the index array could be constructed:

Image
hi rray,
i used your way, here is a result very nice i think :), but still have a little problem (you can see it in a movie below) i think i need to delete the last strip mesh at that time i create a first strip ..
thank you very much! :ymhug:

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rray
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Re: create mesh from strands? not extrude along strands

Post by rray » 22 Jan 2016, 20:13

Hi anhungxadieu
I'm not sure what is happening, it's difficult to say from the video, can you send the scene here/or instant message?
softimage resources section updated Feb 7 2019

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mattmos
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Re: create mesh from strands? not extrude along strands

Post by mattmos » 22 Jan 2016, 22:15

Do you really need the strands? If you're just wanting to create a polygon trail behind an object or curve, could try this (link to scene file on vimeo page):


Bullit
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Re: create mesh from strands? not extrude along strands

Post by Bullit » 23 Jan 2016, 01:23

I don't think that is what been asking since it requires strands.

anhungxadieu
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Re: create mesh from strands? not extrude along strands

Post by anhungxadieu » 23 Jan 2016, 04:23

rray wrote:Hi anhungxadieu
I'm not sure what is happening, it's difficult to say from the video, can you send the scene here/or instant message?
@rray __ sure! this is my scene softimage 2015 sp2, please take a look, thank you! :x
@mattmos __ yes i already checked this before but it's quite difficult for me to understand what going on ... :-s
--> i want to create the trail effect like Yujaeho's movie, it think he create it in Houdini but i want to try it with Softimage
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Mathaeus
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Re: create mesh from strands? not extrude along strands

Post by Mathaeus » 23 Jan 2016, 11:21

anhungxadieu wrote:
--> i want to create the trail effect like Yujaeho's movie, it think he create it in Houdini but i want to try it with Softimage
There's sort of cloth simulation in this movie too. Probably maximum, what Houdini cloth can do :) (now I couldn't resist...).
Now seriously, cloth sim gives idea for another trick, to use just a plain grid primitive and stick to strands. Where strands are generated as particle trails, with appropriate factory nodes, using fixed strand count. Particles should be generated from curve, attached to moving object, to get an nicely ordered distribution of first row. Modulo formula should be something like point ID of mesh, divided by count of second row, to feed into ID to location. Later, select in array of strand positions (had something similar in some compound, for attaching strand extrusions back to point cloud with strands).
Grid comes later as an target for Syflex Mimic constrain - which could be animated to zero weight in pre roll phase. That is, thing should have a pre roll of at least the same number of frames, as strand trail have segments.

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rray
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Re: create mesh from strands? not extrude along strands

Post by rray » 23 Jan 2016, 20:14

I'll have a look at the scene. my suspicion is that the point order gets messed

If the number of points stays constant, Mathaeus idea with simply moving a poly grid's points around is better. Then you'd be able to use motionblur too.

Here's a nice related video (ofc made in Softimage)

softimage resources section updated Feb 7 2019

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rray
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Re: create mesh from strands? not extrude along strands

Post by rray » 23 Jan 2016, 22:25

@anhungxadieu issues were:

* The points (IDs) were in order, but the "build array from set" node doesn't use this order anymore after points have been deleted. So "build array from set" has to be used on the IDs, and then that as the key to sort the other array (plus some messy tricks in this case because the strandpositions are arrays themselves)

* there was a multiply node missing in the screenshot I posted :ymblushing:

* "thuy strand create loft" needs the pointcloud's nbPoints attribute plugged in the nb strand input
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softimage resources section updated Feb 7 2019