Theoretical SUB-D

#841

Hello everyone …! I’ve been newly working on modeling and I have a simple problem again but it’s crucial for me to understand this to get the principles and basics of polygonal Modeling. If you look at the images below you’ll get the idea . . .

I applied solid chamfer to an edge group and it gave me 4 pentagons.
My question is : What cuts do i need to quadrify it to a stage where it doesn’t give me the slightest pinching when meshsmoothed?
I really need to figure this out. Thanks everyone . . . Take care !

#842

I know exactly what you’re talking about, check this thread out:

http://forums.cgsociety.org/showthread.php?t=308658&page=1&pp=15

The conclusive answer seems to be to build it as cleanly as you can, then just fiddle until it hopefully doen’t pinch.

#843

custinyakis:

You have ngons at the corners. Tie-off those ngons with quads or tris and it will eliminate or reduce the effect.

-Dave

#844

A Lovely Thread !!! . . . Thank you so much Unkle Bunkle.

Dave Black, can you show me what I can do to reduce the pinching of the edges ??? with some simple lines in photoshop on the image ? I would really appreciate that. I’ve been reading this thread for a very long time and I learned a lot from it. To make a square hole on a sphere for example( This is a very similar problem with this one isn’t it ? )

By the way I changed the previous images’ resolutions . . . they were disturbing the overall design of the page. Sorry about that : )

Some people are using Rhinoceros NURBS for complex industrial designs instead of Sub-divs. Why are they using Rhino ? Are NURBS tools in Rhinoceros better than the NURBS tools in Max ?
And what what happens if I animate, bend, twist a NURBS model ? Are they animation friendly ?

Thanks everyone who type even a single word to this thread. Take care !

#845

I would try this (see image). What appears to be a tri is actually a quad. The edge running through the center of your chamfer terminates there giving it its 4th vert.

#846

Methinks that cut will create pinching, that’s a very narrow polygon within the rest that are mostly quite huge.
I’ve found that you want to keep all the faces as similarly sized as possible, this way when it smooths it won’t pinch so much.
Think about it this way, when it smooths it adds lot’s of divisions between edges, if you have wide spaced out edges then 2 that are really close, when it smooths this’ll pinch (unless on a flat surface).

#847

Option-cg thank you … I tried that but it did not prevent the pinching. Moreover by this way you only make the triangle a quad polygon but others remain pentagons. Through this conversation I come up with a new question . . .

As I’m reading the tutorials in some 3D CG Websites I see that lots of the modelers use triangles & ngons in mechanical polygonal models. See the images below . . .

What about the ‘‘All-Quads’’ ? Can we use traingles & ngons in some cases ?

Unkle Bunkle you’re right !! The same-sized polygons are definitely better.

** Actually I don’t have permission to use these images. They are from the tutorials of Munkmotion and David Melchor Diaz. Hope they don’t get mad ( :

#848

custinyakis: I think that in certain situations it works just fine. The examples you give show poly’s which are in a co-planar <? (parralel / uniform surface) with which any distortion in the resultant subdivision would be pretty much flat and hardly visible if at all. Reflections may be distorted though? I think…

#849

Hi, i resently started to try using sub-divisions for some technical illustrations, but the results arent what i expected. isnt a box supposed to turn into a perfect sphere when subdivided? my problem is, that i need to create a cylinder shaped plug and i wanted to use a subdivided box(since modeling with a box would be much easier) to create one but it does not turn into a cylinder. =/

#850

Awesome, this is a big help for me… i was having some real tough issues figuring out how to make this sort of geometry. Thx

#851

This is a very great thread, i’ve spent all day reading this valuable resource

my only concern is, the first 20-30 pages arealmost useless since most of the images are already gone.

i guess it will be very useful if anyone use image attachment so we can still see the image
all the time (i know it will be hard on cgtalk server though).

#852

Thought this may help http://www.tweakcg.com/forum/viewtopic.php?t=251
middle of the page.

#853

Following on from what Tony Richardson has been posting, how about this arrangement for extruding a square shape on a curved surface etc and keeping everything 4-sided? Such a tricky thing to achieve without distortion! Interesting thread though. Would love to see some more options.

#854

Time to revive this thread again…

I’ve been doing a lot of technical modeling lately, and to make things worse it’s for Mental Ray which in our current pipeline won’t support n-sided polygons. Cool :slight_smile:
(another fun part is if you want to use Zbrush on the result… :P)

Some notes…

  • In general, it’s very important to choose a right level of detail for your control cage. Everything is fine and cool as long as you’re trying it on a cube, maybe even on a cylinder; but build something more complex and you’ll discover that the techniques explored in this thread can fall apart very quickly. Drilling holes into an 8-sided cylinder will cause a lot of pinching no matter how clever you are; using 16 or 20 sides or even more will make it a lot easier. The same goes for more complex shapes too, like cars, armor and such.
    It’s pretty much the key part IMHO. Yeah, the point of subdivs is to use a low res control cage, to keep the final poly count down, and it’s easier to work with less polys, too - but give it a try. See, as you start to add extra edges around your holes and extrudes, they’ll create small, thin polygons near the large, wide polygons and that’s what distorts your original shape. Now if you already have small, thin polygons, the difference will become smaller and thus the surface distortion will be a lot less noticeable.

  • To get a nice smooth shape with properly flowing curves, it’s a good way to start as simple as possible and work your way up procedurally. Build a low poly version of your model, and apply a meshsmooth to get nice, evenly distributed quad polygons. Use open edges to influence how the meshsmooth works. Use the shell modifier a lot, too.

  • Use turbosmooth’s isoline display and the lowres cage together to study how far edges are moved away from their original position because of the subdiv smoothing. Add extra loops when neccessary to keep them where you want them.

  • Surprisingly, triangles can work pretty well in many cases.

  • Constraints are your friend, use the edge constrain to preserve the surface shapes as much as possible in the final stages of the modeling. Avoid manual, ‘freehand’ point pushing like the plague.

  • Another surprise is that messy stuff -can- work pretty well. Sometimes it’s the only way.

  • I imagine that polyboost must have a lot of cool tools to aid you in technical modeling, too…

Now, the thing that’d probably close this thread forever would be to somehow dump Fausto’s mind into here. You know what I mean:

I’d love to see a wireframe of THAT.

#855

The funny thing is that I think that the wireframe for the marine is actualy quite simple. Take the lower leg armor for example. “All” you have to do is to get the general shape done, then subdivide it and/or cut the panel lines in. Clean it up, add the little holes for the bolts and you’re more or less done. The detail on the lower edge (above the “boot”) can easily be done with the shell modifier and a spline for the profile (you can see it in the waist area too). What makes it look awesome is the stupid (and I mean that in the best possible way :D) amount of detail and the general design. If you disect the separate pieces of the armor, you realize that it’s a lot simpler than it looks.

And Laa-Yosh is indeed right, technical/hard surface modeling can benefit from tris, pentagons (5 sided) and all kinds of “no-no” techniques :slight_smile:

#856

this thread would answer so many of my questions if only the images were still available (and the same goes for a few other threads)! does anyone know if the pdf/faq was ever made?

in trying to learn 3d modeling (and in particular, subd modeling), and i’m discovering many of the fantastic issues that subd’ers get to wrestle with. say i want to model the robot from Laa-Yosh’s post (2 posts up from here) with all that kind of detail. would you guys say it’s quicker with subd or with nurbs?

i haven’t really used nurbs as i prefer the ‘mouldability’ of subd’s. i have heard that nurbs are tedious to work with and that there are issues at render time - what are the main problems and do you think they are less or more of an issue than tweaking verts to get mechanical/hard edge details to look right on subd models?

also, i’ve bought a few modeling dvds that go into hard surface modeling, but there is very little dedicated to subd DETAILING and the bit that i did see i thought showed very poor technique. can anyone recommend a good (and thorough) dvd (grooves/ports on CURVED surfaces)?

TIA

#857

I would reccommend Chris Thomas’ CG Academy DVD Advanced Modeling 2 - Technical Modeling DVD. For 3ds Max tutorials, they really are the best stuff out there.

NURBS/Solids modeling has its place in 3D, and modeling. You need to use what works for you, not what works for other people. Everyones pipeline and workflow is different so don’t base your decision based on what other users do.

-Eric

#858

PiXeL_MoNKeY, thanks for the reply. i have seen the dvd you suggested and although it’s really good, there isn’t much subd modelling technique (unless i missed it!)

i’m comfortable poly and subd modelling on ‘regular’ surfaces (flat, perfect sphere/cylinder etc) but what about when things get more complex? what i’m trying to understand is whether nurbs are quicker than subds when the model gets complicated. (for example the ‘robot’ in the picture that Laa-Yosh posted:

is that even a subd model? maybe it started as subd, was then converted to high poly and then detailed?

are there any dvds around that show how to model these sumptuous curves and details?

#859

PMJI, but yeah I’m 99% sure that is a subd model.

I’ve not had to do anything that complex, but there was some pretty good info in this thread about cutting into curved surfaces, but I’m not sure if the relevant images are still there.

I seem to recall some people lift parts of the model and use the shell modifier with bevel profiles to get overlapping plates, which is a nice technique.

I don’t know of any specific DVDs, but I haven’t really looked to be honest.

  • Steve
#860

The majority of Fausto’s work, AFAIK, is subd’s w/ mudbox for detailing. Check out the wire from this thread, or the wires you can find on his website.

-Eric