How to improve this subd?

This piece of a bigger project is bothering me because of the dimples at some of the intersections. How can I lay this out better so that I don’t get dimples?

dimples.3dm (104.3 KB)

Hi Peter - I am not your huckleberry for this - @theoutside, @BrianJ - over to you…


Here’s an example. I removed the creases and changed the topology to all quad. Tightened up the edges you had with bevel. Not sure if this is what you’re after, but it’s an option.

dimples.3dm (81.2 KB)

Hi Mark,
I really need to keep those hard edges, especially the inside edge. Or do I have to get rid of those creases if I want to pull this off?

If you need to keep hard edges, you should try to have them be complete edge loops/rings. If they end in a pole or starpoint, you will always end up with pretty bad wrinkles. Does that help?

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Ok, thanks

Can’t we “weight” edges in a SubD to make it look like creases (actual creases)? Should be pretty much self-sufficient as a replacement. Actually, it will be even better than a replacement.

There should be a different term for inner and naked hard edges: ridge (!?). Crease is more like a small (narrow) G2 fillet.

Peter, could by any chance export the control point wire-frame of the SubD object?

Here is the concept in MODO (from 2018):
(MODO - SubD edge weight)

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I did some experimentation with “weighted edges/verticies” in another program. Could not find any “weight edge” command in Rhino 7 regarding SubD, so… this is a fast mockup from your poligons.

I know that weighted edges are on the wishlist for subds, so maybe that will help down the line.

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Keep in mind though, that you would still need close proximity edge loops (the rule of three edges/points to make a sharp corner on a surface/curve respectively) to the weighted edges, otherwise there will be “flat” areas around the weighted edges… as you can see from my mockup.
Weighted edges are ideal to make creases (actual creases). Hard edges (ridges) do not exist in reality anyway, unless we are talking about knives and sharp blades.

Anyway, who am I to talk about proper terminology… actually the word ‘edge’ is more than enough to describe ‘hard edge’ or ‘naked edge’ and not a crease.

Sharp edges in the real world may be rare, but I need them in 3d models. In any case, I know my part doesn’t follow the rules of subds, which is mostly why I’m asking for help.

Yes, I understand that. But then if you really need sharp edges in that layout, you will experience shade artifacts at “star points”.
If you are not doing it for 3D printing or any sort of ‘real production’, only for visuals, I would suggest building two objects one without the ‘sharp edges’ details and one only with ‘triangles + sharp edges’ and overposition them on top of the smooth object.

Quick SubD tweaks in Rhino 7 of your file:

  • most likely not what you have in mind, but it is difficult to understand (car modelling with creases is not done this way anyway)
  • have to play with insert loops
  • every “crease” should have its own face loops: to make them disappear/merge with flow just make the end verts of end faces closer together
  • so, mine is also not correct in that respect but I wanted to show you what is the usual way
  • hence, you will nede three main face loops to “host” each of the “creases”
  • the perpendicular one you will have to figure it out yourself at the end of the task

dimples1.3dm (59.8 KB)

I’ll do some more experimenting. I’m not modeling a real car, this is plastic ride-in car for kids fwiw.

Thanks for your help!

SubD sharp (weighted) edges were recently added to Rhino and are available in the current Rhino WIP. More information here:

Rhino WIP feature: SubD Sharp Edges (weighted edges)

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