How to Create Perfect Cubes with Conic Corners?

rhino
rhino5

#1

Hi!
I’m having trouble to create conic-corner-cubes with perfect curvature.
I used “rounded rectangle - conic corners” and “rail revolve” to create a few rounded cubes in-between a sphere and a cube. The curvature of faces parallel to the revolving axis (as shown in front view) looks perfectly smooth; but the curvature of faces perpendicular to the revolving axis (as shown in top view) has sharp turns. In rendering mode, it looks slightly edged.
Is there a way to create these cubes with perfectly smooth curvature at all faces? Thanks!


#2

I think this is maybe a step back from what you want, but it’s how I made a curved cube. Perhaps my approach can spark a better way. I cut away a square section from a sphere to make the faces of my cube. Bring the faces mid points together and trim them, then use variable radius fillet.

After starting to write this I realised the quicker way to make the cube is to use six spheres and boolean split them. That leaves you a central cube that is perfectly trimmed. That is the cube with zebra stripping below with radius edges.


#3

Forgive me I do not write and speak English well. How do you position the 6 spheres to make the bolean?


#4

The spheres (170mm approx dia) are placed so they overlap, about 50mm in this example, that produce a cube with 3mm bulge to the surface.

x4 polar array from top can produce the sides, then a copy rotate x2 to do top and bottom. Now boolean split the lot and pick out one of the cubes in the middle, delete the rest.


#5

I can play it. Great to know


#6

You’re not limited to just cubes, you can use elliptical shapes or different parts of a sphere to generate some great shapes then apply different radiuses to the edges.


#7

naturally. Thank you


#8

Wow, it’s really interesting to think of a curved cube with six spheres!
I’ll try creating some conic curved bodies first, then place and boolean split them.
I’m a little obsessed with all kinds of conic curves recently haha.
Thank you for the inspiration, Bill!


#9

Just realized my circular reasoning…
I want to create a curved cube with conic corners like this:


The conic corners have identical rho (a parameter of conic curves. If it’s 0.5, it’s parabola; larger than 0.5, hyperbola; smaller than 0.5, ellipse) and tangent in the mid point of the cube faces. So boolean seems won’t lead me to these corners.
I tried “Blend” yesterday, but it has a different parameter, so that though it can continue the curvature, it won’t keep the conic rho, unless I know how to translate and equal these two different parameters.
A bit OCD here lol… Grasshopper may do the job?


#10

@Bill_Carson i can’t seem to manage your method, whats the best way to pick out one of the ‘cubes’ in the middle after boolean split ?


#11

Select the centre section and drag it out… Otherwise switch to wireframe view and select a cube edge and drag out.


#12

Rhino needs a Superellipsoid object. Check out the Wikipedia article on Superellipsoids.