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Old 21-01-2010, 03:45 PM   #1
El Burritoh
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Default A couple of questions about hard-surface best practices...

I have a couple of question I'd like ask our hard surface modelers. I know John has been posting around here so maybe he has some insight... Anyone else who has experience to share, please do so!

I'm a modeler at a studio in the U.S. and although I "can" model just about anything, I do better with hard-surface assets.


1) Edge Weighting

Whenever I'm sharpening up hard edges, I always use actual geometry to do so, by either adding edge loops or sections of edge loops. I've been tempted to use edge weighting, but it never works into my workflow (where geometry will pass between apps and the edge-weighting data would be lost). In the context of a larger studio like Weta, how are edge-weights viewed? Are they frowned up for pipeline reasons (or other?), or are they a perfectly acceptable modeling tool?



2) N-gons

This is still related to hard-surface modeling... I have always heard that n-gons are of the devil and must be avoided at all cost (and for organic stuff, sure). But in actual practice, for surfaces that aren't going to deform, I have found that some 5-sided SubDs actually render better than if the patch had a triangle in there somewhere. It's not always the case, but frequently I will try to make a section all quads and tris, only to delete an edge and find that as an n-gon, the tension balances out and the darn thing actually looks better! I have heard from other hard-surface modelers in the industry that n-gons on non-deforming surfaces, especially if the surface is flat, is okay in many situations. Is this the sort of thing that depends on the studio? Or now that Catmull-Clark type SubDs are the norm, are n-gons pretty much okay?
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Old 21-01-2010, 05:22 PM   #2
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here is a cool video from Greg Petchkovski about topology to avoid smoothing artifact etc.

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Old 22-01-2010, 03:22 AM   #3
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Thanks, Nicolas. I've seen that vid before and it's very helpful, especially for the puzzle work of getting rid of unwanted 3-5-sided polys. Very good stuff.

I guess I'm just wondering if the use of n-gons is strictly prohibited in some studios, or if it depends on the usage of the model, or if there aren't any artifacts on a hard-surface model, does it even matter? I know the discussion is still ongoing as technology progresses. Just wondering what the philosophy at the higher levels of the industry is.

And I am referring specifically to hard-surface modeling because those surfaces don't really deform like organic models who need to be rigged to flex and bend.
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Old 02-02-2010, 07:35 AM   #4
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Anyone else?
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Old 02-02-2010, 10:00 AM   #5
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Hey El Burritoh

1) Edge Weighting
I know of it but I rarely ever use it for Hard-surface models, And this is due to the reasons you pointed out, to many different part of a studios pipeline and to many different tools. Sometimes the simplest option is the best option. So I tend to lean toward keeping everything a geo.

So really it just down to the studios pipeline and the best way you work with it

2) N-gons
You do pick the dangerous topics . From what i have found and heard its very much down to either the studio having a preference or the modeller themselves.

Personally I try to avoid n-gons and just replace them with tri's where ever we can. There are some render related issues that can arise from using these as well.

So yet again its really just down to the studios pipeline or the modeller.
I kinda feel like I haven't answered your questions, but at the same time its very hard to give an answer considering the amount of variables, what use, what pipeline etc...
Just my 2c, Hope it Helps,
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Old 02-02-2010, 11:14 AM   #6
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Thanks John, that answers quite a bit actually!


You've piqued my interest about n-gons causing memory problems for spherical harmonics. I am familiar with spherical harmonics as a solution for image-based lighting, but I'm not familiar with how n-gons affect that. Is this an obstacle unique to certain rendering engines, or is this an issue with spherical harmonics in general?
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Old 02-02-2010, 01:18 PM   #7
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To be honest I am not sure on the technical aspect of it.
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Old 02-02-2010, 02:53 PM   #8
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Hey thanks John, that did answer a lot, I would like to know why you guys sub-d your stuff at render times? is it because of Stand alone render engine?

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Old 02-02-2010, 03:15 PM   #9
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Its down to a few reasons, not all related to the Models dept. Cant speak for the other dept, But for us anyway, modelling hard-surface in polies is alot easier and quicker then true subd's. No reason to model in subd when your render engine will just convert polies for you?
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Old 02-02-2010, 03:24 PM   #10
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yeah that does make sense. I just didn't understand why you guys would subd it at render times.

Thanks so much

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