[solved] How to transform a sphere to a planar grid ?

[sebkaine]

Hi guys !

I am trying to transform the point of a spherical object to match a square 2D grid.

I have succeed to do the invert operation , i have a square grid and i transform it into a sphere with the creep node.(cf attach file)

But i can't figure for the moment how i could achieve the invert op ?

If you guys have any idea , it would be great !

Many Thanks

E

spherical.hipnc

Edited November 21, 2013 by sebkaine

[Milan]

I'd try creating nice polar uvs on the sphere first and then copying 1st and 2nd uv component into X and Y position of the corresponding point (and 0 z of course), that should give you correct result.

However poles on your transformed grid have 100 points in the same spot so if you need to do it from standard sphere which these merged into one, you'll need to split the sphere poles on either end first, to get matching number of point compared to your grid.

[acey195]

You could also use a cube, if you first UV-map it and then subdivide it to create a sphere you can easily go back and forth between 3d and planar.

using the UV coordinates, like Milan suggested. But by using box UVs, you will generate less overall stretching than with polar UVs.

note that you may want to incorporate a ray node after subdividing, after that you can simply store the point/vertex positions in an extra attribute.

Also note that by using vertex attributes you get better results at the borders of the UV map.

[sebkaine]

Guys This is Brillant ! Many thanks for your help , i will try to make things work and post the scene after it works correctly !

Cheers

E

[magneto]

You can also turn a grid into a sphere using 2 bend operations. You might have to implement your own bend though

[anim]

depends on what you want to use it for but

in your scene you have planar grid wrapped to sphere, if you add rest position before Creep SOP they after creep you can sample rest at any location on that wrapped sphere and you'll get original grid position back

[sebkaine]

Thanks for the inputs guys , i will try all your ideas and see what works best for my case.

Basically i am shattering a sphere so

- i draw my shatter in illustrator

- i shatter a planar grid with cookie sop and a for each

- then i transform my grid to spherical coord with the creep

All this works , BUT like you guys mention when you warp a grid like i do with the creep you get a really bad topologie in the pole area where all points are merge together !

so i have to figure now , and i haven't solve this yet , how to

- convert a 2D grid object where you can work your shatter in UV space (you use the UV layout of your sphere in polar projection to draw)

- convert it to a sphere by keeping your shatter in the good place ,

- but when you apply the sphere transform you find a way to get a decent topo at the pole of the sphere ...

so the only 2 way i guess to solve this are

- Modify the method to go from planar to sphere (creep...) ?

- Modify the topology of the 2D grid by deforming the topology to anticipate the deformation ?

I let you know if i find something good enough ... if you have any idea ... it would be great !

Edited November 20, 2013 by sebkaine

[sebkaine]

I think that starting the shatter from a grid that has the topology of my UV layout is the easiest way , but i am facing one new problem.

The exact same than this dude :

http://forums.odforc...ote#entry102500

Thomas on this one you solve the problem, but not the Vertex to Point promotte problem.

I know that UV should be vertex @ but it doesn't help my buisness , so if someone has an idea on how to

- take the uv Layout of an object at vertex level

- create a planar grid that has the exact same topology than this UV layout ( and not the messy poly at the edge ... with point promotte )

- store the rest pose in each point of this grid

- then reapply the orignal posistion

My problem would be 100% solve !

Thanks for your lights guys !

EDIT :

pb solve, i post a scene in case someone has the same PB

Thanks again for driving me in the right direction !

unfold_refold.hipnc

Edited November 21, 2013 by sebkaine