Vellum's bend-stiffness control

[tagosaku]

hi, I try to use vellum in order to create TreeFX. Then I took two tests with Lsystem, and vellumsolver with wind and standard gravity:

1 - apply polywire and vellumCloth. 

2 - apply just vellumHair

I set bend stiffness a very large number for the both tests, but branch still bend so much, cannot make stiff well. Setting more substep helps not to bend, but not enough.

Does anyone succeed to control bend parameter very well?

 

 

vellum_v0002.hipnc

Edited January 3, 2019 by tagosaku

[Noobini]

low res geometry bends less than high res geos.

Same idea as if I ask you to bend for me a 1x1x1 box. If the box has only 1 segment in any direction....you'd say how the hell can you bend it ? Yes 1 segment is a bit extreme...but it illustrates the point...so lower the segments count of your branch...upping the segcount is a mistake.

Simple comparison, same Hair settings for both lines, since it's simple....I even left substep at 1...for other cases, upping the substep can help too.

vu_BendStiffness.hiplc

Edited January 3, 2019 by Noobini

[Noobini]

Bush.....not George Dubyah...

So if you play with resample, even upping the segments by just ONE...it makes it that much harder to keep it stiff..

vu_simplevellumbush.hiplc

Edited January 3, 2019 by Noobini

[tagosaku]

To Vusta

Thanks for you reply. Yeah, I tried your hip file. Motion is very unstable and animation never stop. I think we need something new ideas to make a wire simulation. Otherwise I need to cheat to set gravity zero.
Of course, the stretch prevention is so much better than a traditional wire sim. I was thinking vellum could replace the wire sim but maybe not...

[Noobini]

well obviously it's the wind...if you don't like the wind....simply disable/delete it in the solver....

Just thought I'd add some 'spice' to the scene that's all.....

[Atom]

I like this solution, it seems to respond to stiffness fairly well.

I added a slight sin based wind along the z-axis.

sin($T*55)*2

 

ap_vu_simple_vellum_bush.hiplc

[tagosaku]

To AtomicPerception 

Thanks for your reply. I took a look at your file, too. So far, important parameters to keep not-bending are:

resample node > max segments 1 or 2 (more than 3 are bending a lot)

GroupExpression node > @P.y<0.25 0r 0.5 (How many particles to pins also effects a lot. In other words, Pinning only a root particle is not enough)

vellumconstraints(hair) > stiffness 1e+10 and dampingRatio=0.1 is pretty good. (1.0 makes bend a lot. 0.01 makes to keep moving/shaking.)

VellumSolver node > set constraintIte and substeps larger numbers make less bending

After that, I added subdivide node, instead of resample. Then wire gets smooth&curvy. 

 

 

Edited January 4, 2019 by tagosaku

[Neeson]

How would you go about attaching objects, like berries or leafs to the branches? 

Edited January 10, 2019 by Neeson

[Noobini]

well it's just an attach to geo constraint.

OR cheat....after the sim has finished, simply randomly select a few points out of the branches....copy 'fruit' to points...

[anim]

if you want branches and fruit to mutually affect each other you can use stitch constraint or glue constraint

attach to geo is just one way constraint 

[Noobini]

20 minutes ago, anim said:

if you want branches and fruit to mutually affect each other you can use stitch constraint or glue constraint

attach to geo is just one way constraint 

oh yeah, ok, never considered that '2 way action'...

[tagosaku]

On 2019/1/11 at 8:34 AM, anim said:

if you want branches and fruit to mutually affect each other you can use stitch constraint or glue constraint

attach to geo is just one way constraint 

yes, that's true. Question would be how to attach leaves/fruits on tips of branches. If anyone find tutorials shows how to create/construct real tree, instead of using the speed-tree, it would be great!!

Or if you can just tell me how to detect the end of wires or tips of branches, it would be very helpful, too. I think I have to use VEX like a primvertexcount in order to find points that share only one vertex, which should be tips or beginning of root. 

 

[anim]

8 minutes ago, tagosaku said:

...Or if you can just tell me how to detect the end of wires or tips of branches...

 

[Noobini]

here's my foolin' around.....certainly cannot claim to know what I'm doing...just exploring...(prolly extremely inefficient method)

 

vu_treetips.hiplc

[andehpandeh]

another thing that helps with lowering bending is to scale up your geo (x100) before simming, and scaling it down after caching