Procedually unfolding

[dynamoanders]

Hi guys.

I´m trying to grasp the procedual understanding of Houdini and it somehow feels like it´s possible to do an procedual unfolding of, say a folder, without rigging and skinning it with bones?

Like creating groups and controlling it with chops? It feels like my biggest issue comes to how to procedually place the pivot at the right place. (I´m thinking thickness to the geometry too).

One more idea is doing it with L-Systems, attaching geometry to it?

Kind of like this,

//Anders

[hopbin9]

lol, I can remember a couple of years ago I had to animate a box rolling around in 3ds Max. After reading several tutorials on the subject, it was a complex task of animating the pivot points and moving objects.

Houdini makes this kind of task so easy and flexible it's not even a challenge. You're learning the right tool if this is the kind of stuff you want to do.

I've attached an example of unfolding in a straight line. You could easily create a subnetwork of the line and repeat for changing directions.

unfolding.hip

[Macha]

I like hopbin's method.

For more organic unfolds you could also use a cloth sim with a rest position, but is likely to go wonky very easily.

[dynamoanders]

Hello again.

Yes, that´s kind of what I was thinking of, thank you, hopbin9.

Coming from a 3DS Max and Maya background, I´ve been doing these tedious things before (as you), but what dragged me towards Houdini is the procedual workflow and it feels like some many problems I used to have, and had to learn MEL, is just somehow integrated into Houdini. There´s just soo many possibilities of speeding up complex tasks. Just love Houdini.

One question though, this feels like it wouldn´t work with UV:s (having the same on every box?). Some further testing I will do.

@Macha, yes that would give it an interesting look, maybe baking out some bgeo and try later, just trying to get my head on the workflow in it.

Thanks again guys

[hopbin9]

What do you mean by UVs? You want different UVs on each box, then add that in the Copy SOP or apply UVs in the box animation for all of them to be the same.

Rather then is a DOP network to smooth the animation. I'd use a simple chain of bones and animate it by hand. Giving it a soft curl as the box turns (if you want a page turn effect).

[breadbox]

I have been working on this problem for a little bit now. I have a few references:

The second one is by myself, was created with a python script in maya that works by turning an edge selection into a joint chain, it automatically detects the rotation orientation based on the edge and the angle of the previous and next joint. also I range mapped all the joints to one global slider so you have a fold control that will roll the entire joint chain.

I have looked at the C4D one, and it has some similarity, you create a hierarchy of faces and an xpresso controls the fold degree of each face. The C4D one does not account for angles that are not 90 degrees though which is no good.

Now my attempt in Houdini. I have a pivot position and a point normal vector to rotate on. some things are working pretty decent so far, what I need is to figure out what the best way to create a kind of recursive hierarchy among the faces. I thought to use an ordered face list and maybe a for loop would do it.

what I'm doing in the for loop is trying to calculate the rotations of the previous face and apply that rotation to the next face in the loop. but I think i need to apply rotations for all the previous faces like a joint chain would.

A-B-C-D

A=A

B= B+A

C= C+B+A

D = D+C+B+A

I think you can write a shorthand if the faces rotation matix are calculated in the correct order.

D=D+C

C=C+B

B=B+A

A= A

I'm not sure what the best way to merge or stack rotation matrices together is im assuming the vopSOP is the way but I need a method to store all the information so each face can access it properly?

BW_recursiveRotate_v5b.hipnc

[yesyes]

can foreach loop provide us some help to achieve this easily? we can find centroid easily of each plane. pivot can be placed at some distance from centroid maybe