8 replies to this topic

[ScottishCpt]

Greetings to all.

I have a whacky question here that I have been unable to get a good answer on.

When I learned how to model with subdivision surfaces (well, I wouldn't say "learned"- I'm still learning), I did so with the aid of a few tutorials and basically made up my own mind on the rest. In retrospect, this may have led to a few bad habits.

What I've noticed when modelling mechanical parts (basically, anything with a flat surface) is that I need to double-edge everything if I want to assign that mesh a highly reflective material and expect the reflections to look perfect. If I don't, then the resulting reflection "looks wrong" in that what should be a flat surface has a slight bit of warping to it near the edge of the geometry, which is readily visible in any reflection.

As far as I know, I'm probably the only person on the planet who does this (which makes me think I'm wrong). I've also been told that this is wrong by other more successful modellers then myself. Yet, if I want a nice uniform surface that has an uninterrupted reflection- I can't think of any other way to handle it.

So I'm wondering what your opinions are.

Am I wrong? Is my modelling form incorrect? Should I only be using one edge loop? The imperfections this seems to introduce are visibly undeniable, so is it simply something that most people ignore on the basis of things being that much easier to model?

I've attached two pictures highlighting this issue.

In the first, you can see the surface of the left model warp slightly near the edge of the model. The right model does not share the same imperfection because everything is double edge looped.

The second picture is just a wireframe render of the first, so you can see what the geometry looks like.

Cheers,
-SC

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[Anthony Owen]

I think the one on the right looks best.

[Fastbee]

Double edging should not be needed. Both reflections look perfect to me.

[rustEdge]

Actually you're correct. You need to double that double edge to get flat surfaces. P=

Two parallel edges will curve down that fillet, but there would still be a bit of warping between the supposed flat edge and the fillet. Basically HyperNURBS behaves like a 3-dimensional B-spline. The curvature of each face is affected by it surrounding edges, plus the edges surrounding adjacent faces.

That is also one reason why people create edge loops that run parallel to edges they want smoothed, to isolate the curves from the rest of the mesh.

[CollinBishop]

Have you tried setting the hypernurbs subdivide UV'S to "edge" detection? This will allow for proper smoothing without the need for the extra loops Add ing extra loops is not the correct way. I have attached a tutorial I have made showing the process of UVing and this smoothing is spoken about when I unwrap it and apply a checkered pattern. You can clearly see how it affects the edges.

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[Fastbee]

If you are talking about having the geometry of the object be perfectly flat after putting it in a Hypernurbs object doing a second edge does make it a little more flat, but not perfectly flat. When using a hypernurbs object I am not sure it is theoretically possible to get a perfectly flat surface even with 5 or more edges. The best way if you do want the flatest surface possible when using a hypernurbs object would be to select the edges of the flat surface and use hypernurbs weighting. Next select the surface you want flat and make hypernurbs weight that, but not all the way or you will get intersecting geometry that will cause glitching. This would be the best way to get the flatest surface possible.

Cheers
Fastbee

[rustEdge]

Yep, it's practically impossible. Unless you use HN Weighting, The only way to get a completely sharp edge/flat face is to have edge loops lying exactly on top of each other. Of course it's not good practice to do something like that...

[hulaboy]

Increasing the overall mesh density in open areas to get a more uniform topology can also help with 'flattening' under sds. Too little geometry can sometimes be as problematic as too much, especially if there's a wide variation within a single mesh.

Mark

[mikeynz]

Use the Bevel Tool!! (convex 5x subd atleast)

I don't think there is a need to be using hypernurbs at all for this.


If I was to model this in Rhino or Solidworks I would just fillet the edges I want rounded.