Subdivided sphere issue

[Skybar]

I got a couple of spheres I want to render with refraction. They are pretty low res, and I wanted to subdivide them at rendertime. However the poles get all screwed up (see pictures) and this is clearly visible in the refraction. I've noticed this lots of times before but it never really was an issue. 

 

Is there an easy fix for this? Probably a noob question but I have no clue really. I could go back and use the "polygon"-sphere (made up of only tris) instead, but then I'd have to resim and all that.

 

Cheers!

 

[Atom]

When I want a sphere without pole issues I will use a sub-divided box.

Edited January 11, 2016 by Atom

[f1480187]

You can idealize bad-shaped sphere with something like this:

vector min, max;
getbbox(min, max);

vector center = avg(min, max);
float radius = avg(max - min) / 2;

// Spherify.
@P += center;
@P *= radius / length(@P);

// Spherical normals.
@N = normalize(@P - center);

Replacing geometry completely with NURBS sphere using Match Size SOP is the best solution, probably. Why have to resim?

spherify.hipnc

Edited January 11, 2016 by f1480187

[Skybar]

That's great! Thanks a lot

[acey195]

When I want a sphere without pole issues I will use a sub-divided box.

or use a geodesic "Polygon" in Houdini sphere topology

 

 

if you want to subdivide afterwards,

I would still do this in combination with something like the vex wrangle mentioned before.

 

especially if you are using the subdivided cube approach

[Noobini]

i gotta admit...noobs like me got it easy these days...just take a look how easy it is to Spherify something in H16...and set normals in the same node...but what if the object is not at Origin ? well dive in the file and see...

 

more shenanigans in video..

 

Spherify_H16.hipnc

Edited June 23, 2017 by Noobini