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alteredgene
03-14-2011, 11:17 PM
Hi community! been doing some modelling and came across a challenge i could not find straight forward answers to.

basically i am using lowPoly+subD modelling technique. and its hard surface model. its based on extruded octagon, which with turbo smooth becomes a perfect cylinder.

simple extruded octagon
http://dl.dropbox.com/u/6043701/subDquestions/Q01.jpg

extruded octagon with turbo smmooth applied
http://dl.dropbox.com/u/6043701/subDquestions/Q02.jpg

from here, i am merging more complicated shape on the base, and found that i need to add more segement to extruded octagon to fix artifacts and to create a clean loop. basically ending up with extruded 9sided shape as below.

http://dl.dropbox.com/u/6043701/subDquestions/Q03.jpg

obviously, when i turbosmooth this, its no longer a circle,

http://dl.dropbox.com/u/6043701/subDquestions/Q04.jpg

so the only solution i could come up with is to move the adjacent vertices around to "mold" it back to circular shape

http://dl.dropbox.com/u/6043701/subDquestions/Q06.jpg

well, i am thinking this is really not an elegant solution.

one its not really accurate, and end of the day, its not a circle anymore (if you were to zoom in close, the circle is broken severely, unless i start going in and editing other vertices which i rather not)

basically, i run across this problem often, where i start with perfect octagon, everyting subdividing fine. but as soon as i have to add other models (such as three tubes coming together) i start having to add an edge or two on the octagon shape, breaking its cylindrical outcome.

was wondering if any one can help me with any known method that works better then this.

obivously, i could just subD the whole octagon, and work with 16 sided polygon, but that is someting i would like to avoid if possible.

anyway, thank you for your time in advance!

really looking forward to any help you can offer!

Psyk0
03-15-2011, 02:21 AM
The hard surface experts will tell you the solution is to start with a cylinder that has more segments.

ezekiel66
03-15-2011, 09:27 AM
If you want to add small details to a large, low resolution subdivision surface you will either have to live with the artifacts/ dents/ irregularities, or you have to crank up the overall resolution of the objects. There is no other secret solution for this, it is a limitation that comes with subdivision surfaces and how the surface is being interpolated from the vertices of the low resolution poly cage.

In the cases mentioned above there will always be those surface irregularities, all you can do is to minimize those distortions by moving the vertices around and increasing the resolution of the entire surface.

alteredgene
03-15-2011, 10:08 PM
Yep, i kinda had the feelign that would be best way to handle these situations.
just that really wanted to keep the "original mesh" as low poly as possible. but rather then wasting time "amending" artifacts and living with consequences, ended up remodelling the whole thing with more subdivision. which like your suggestions ended up being lot easier and more importantly cleaner.

again thank you for your help!
its as important to know what not to do : )

below is the result so far.

http://dl.dropbox.com/u/6043701/subDquestions/A00.jpg

Bonds0097
03-15-2011, 11:08 PM
This is only slightly tongue-in-cheek but nine times out of ten, the solution to most sub-d problems is MORE GEO!, which is to say, add more polygons. The more geometry you have defining a certain shape (such as a curved surface), the less surface deformations you will encounter when you add extrusions and the like. A lot of the times, if you're going to be doing a lot to a cylinder, you'll start with 64 segments or even more depending on what you have to do.

If your final goal is to create a real-time asset such as for games, then you're going to bake all of your detail onto a low-poly mesh anyhow, so it's fine if your high-poly is dense. If you're just using the model for still renders, or pre-rendered animation, then quality should be much more important than polycount anyhow.

I'd encourage you to visit the PolyCount Forums, the technical talk specifically at http://www.polycount.com/forum/forumdisplay.php?f=43. There's a really interesting thread on sub-d modeling and how to solve specific sub-d problems such as adding extruded detail to cylinders or blending complex shapes and the like.

alteredgene
03-16-2011, 07:25 PM
you are absolutely right that nowdays, polycount means little on pre-rendered scenes.
however, i guess i was trying to limit number of polys for easier modelling and texturing purposes later on.

however, at the end, i ended up adding double the side polys to 16 from 8 as that was the only way i could think around it. result is looking lot better!

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03-16-2011, 07:25 PM
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