topic Re: How to Slightly Squish a Sphere? in Fusion Design, Validate & Document Forum

How to Slightly Squish a Sphere?

Anonymous — Thu, 15 Jan 2015 06:13:20 GMT

Noob here. I'm trying to create a t-spline 3D sphere and then alter its shape to be more of an oval. Any suggestions?

Re: How to Slightly Squish a Sphere?

jakefowler — Thu, 15 Jan 2015 08:46:35 GMT

Hi David,

Welcome to the Fusion 360 community!

The way I would do this is by using the Edit Form tool. Once you have made your T-Splines sphere, open the Edit Form tool, and select the whole body (either window-select the whole thing, or double-click a face to select the whole body). You'll see the manipulator triad come up once you've made your selection. To scale the selected objects (in the case the whole body) in any one direction, you can use the line-shaped manipulators from this triad:

The lines I've highlighted are near the arrow pointing upwards, so these are for controlling the scale in the up-down direction. There other similar-shaped pairs of lines will scale in their corresponding directions.

So to flatten the sphere top-to-bottom, left-click and hold this manipulator, and drag downwards to squash the shape (upwards to stretch it back again). If you want the sphere to be squashed in two directions, you can let go, switch to a different manipulator, and do the same thing.

Here's a video showing this (BTW I'm using Shift + Middle Mouse Button to rotate the view):

The corner-shaped manipulators where two lines meet will scale in 2 directions at the same time. And the circle at the very centre of the triad will actually scale the selection in all 3 directions at once. I'd recommend playing around with these, and the other parts of the triad, to get a feel for what they do. In T-Splines modelling you'll spend a lot of time (maybe most of the time) using Edit Form to mould and tweak the shape, so once you're comfortable with how this tool works you'll be well on your way!

Hope this helps, and if anything's still unclear do let us know.

Thanks!

Jake

Re: How to Slightly Squish a Sphere?

jeff_strater — Thu, 15 Jan 2015 16:17:42 GMT

One small related opinion: I have generally had better luck using a Quadball instead of a Sphere, unless I really want to get radial symmetry. The vertices at the north and south poles of the sphere have a tendency to "come apart" if you are not very careful with selections in Edit Form.

Re: How to Slightly Squish a Sphere?

TrippyLighting — Thu, 15 Jan 2015 17:42:11 GMT

I'd add that for this particualr purpose a Quad Ball has much better topology. Vertices that join more than 4 edges such as the poles of a sphere almost always generate som topology problem during editing.

Re: How to Slightly Squish a Sphere?

Anonymous — Fri, 16 Jan 2015 04:45:56 GMT

wow thank you so much, that was perfect!

Re: How to Slightly Squish a Sphere?

Anonymous — Fri, 16 Jan 2015 04:46:39 GMT

Thanks I'll give that a try too.

Re: How to Slightly Squish a Sphere?

O.Tan — Fri, 16 Jan 2015 05:36:43 GMT

It'll be nice if F360 tutorial will tell why would we choose a quad ball over a sphere for example as sometimes when I look at certain models, I thought a rectangle would be better but turns out they'll pick a quad ball.

Re: How to Slightly Squish a Sphere?

jakefowler — Fri, 16 Jan 2015 14:52:33 GMT

Hi Omar,

That's not a bad idea, we'll see if we can put something together like that.

The quadball and box primitives are actually effectively the same thing, topology-wise; choosing between these is mainly a preference on which form makes a more sensible starting point is for your project. Both have nice evenly-shaped faces which makes for intuitive modelling.

The sphere primitive allows for precise rotational symmetry, and is technically smoother (as it has no star points - the quadball, like a box, has 8 star points). On the downside, as Jeff pointed out it's more difficult to work with because the regions around the two 'poles' are tricky to control, and the face sizes are not evenly-distributed across the body (so the initial orientation of the body is important).

For me, the difference in edge arrangement is usually the deciding factor. If you're modelling something where the main feature lines are longitudinal or latitudinal in nature, a sphere makes more sense because its edges run in those directions. If you're modelling a freeform shape that isn't clearly circular in nature or doesn't require circular symmetry, a quadball might be easier to work with. For this shape, I agree with the comments that a quadball might make most sense here if this is going to be subsequently sculpted into a freeform shape (the shape I ended up with in the video probably won't be that easy to work with downstream).

Hope this helps,
Jake