PDA

View Full Version : Sub-Patch-Pinch...why and how to fix?



IMI
03-15-2008, 11:02 AM
I've spent the last couple of hours trying everything I can think of to eliminate this pinching in both Modeler and modo.
Attached is a screenshot from Modeler in standard sub-patch mode. CC mode removes the pinches which are obvious here, but adds new ones elsewhere. No good.
It looks pretty much the same in modo, so it's not a LW thing. I just can't figure out *why* this is happening, and what to do to smooth it out and remove the pinching.
I've tried spinning quads, adding new edges, all kinds of pulling, dragging, scaling, slicing, sawing, cutting in Modeler and Modo... sculpting in modo...all to no avail.
What can I do to get rid of this? Better yet, what causes it? I don't have this problem in any other part of this model, and I have no idea how I got it here.

Anyone have any suggestions?
Thanks. :)

3DGFXStudios
03-15-2008, 11:25 AM
Remove 3point polys if its possible or welt it later where the tension is lower

Surrealist.
03-15-2008, 11:29 AM
Pretty elementary subpatch woe. Check out my tutorial :)

EDIT: You are almost there. You just have to redirect the edge that merges into the point that makes the triangle so that it is a flow of quads. This will require adding an entire row of polys. Or you can eliminate this one edge to simplify if possible.

IMI
03-15-2008, 11:54 AM
Thanks Richard. I did just re-read your tutorial to see if I missed anything. I have it bookmarked, and saved to disk too, and had checked it all out earlier.
What's been throwing me is I have no n-gons, and no 2 point polys, only a few tris, and nothing else abnormal, according to the statistics panel. All points are merged, and so on.
I'll try these suggestions an get back...
Thanks. :)

Hopper
03-15-2008, 11:57 AM
Well?

C'mon man .. it's been almost 2 minutes.

IMI
03-15-2008, 12:03 PM
I was wondering if it was the >4 point polys, and the one with the tri is one of them, but the other pinch to the lower right isn't one of them. I can sort of see how the triangle is causing a problem, but the other problem doesn't seem obvious.
Nevertheless, I'm going to learn how to fix this if it kills me. ;)

JeffrySG
03-15-2008, 01:25 PM
You may not have a ngon but you do have a pole in there. I also find it easier to work out proper topology in un-smoothed mode. Then once I know it's all correct I can adjust it in smoothed view if needed. Can you post a unsubdivided wireframe of it for us to look at? Let us see most of that area (back the camera up a little).

IMI
03-15-2008, 01:40 PM
Can you post a unsubdivided wireframe of it for us to look at? (back the camera up a little).

Sure thing. I've walked away from this for the time being... frustration and all. I add more geometry and lose the curvature. I delete polys and try to rebuild and... it's aggravating. I've only recently begun trying modeling with subpatch and organic shapes, I might add. I could fix this easily by taking it out of subpatch and going all poly-crazy...but...

Also, above I said >4 point polys, should have been >4 poly points....

Giacomo99
03-15-2008, 02:37 PM
That 5-poly corner is what's giving you the problem. (I think that's what JeffreySG means by a "pole.")

The unfortunate realty about working with SubPatch forms is that sometimes one needs to do some substantial rebuilding to maintain good poly flow. When I get stuck like that, I often just make backdrops of the existing views and start over, keeping an eye on the number of polys required to make the form flow properly. Although it's an extreme solution, it's often faster than fixing the problem areas one by one.

IMI
03-15-2008, 02:53 PM
That 5-poly corner is what's giving you the problem. (I think that's what JeffreySG means by a "pole.")

The unfortunate realty about working with SubPatch forms is that sometimes one needs to do some substantial rebuilding to maintain good poly flow. When I get stuck like that, I often just make backdrops of the existing views and start over, keeping an eye on the number of polys required to make the form flow properly. Although it's an extreme solution, it's often faster than fixing the problem areas one by one.

That's actually a great idea. I had already figured I might have to start over, at least with that area, but making a backdrop for reference, I wouldn't have thought of.
Thanks for the suggestion. :)

JeffrySG
03-15-2008, 03:31 PM
Yes, a 'Pole' is a corner with more than 4 edges coming out of it. They can sometimes cause pinching or smoothing in a way that is not wanted.

I'm not sure what that model is, but to be honest, it looks like you have way too much geometry there. I would be pretty sure there is a way to get what you want with much less geometry in it. This will make it easier figure out the correct topology. Post a unsubd wireframe of the entire specific object.

IMI
03-15-2008, 04:00 PM
I can do better than that. I'll post the lwo file itself, if anyone wants to look at it.
It's a rather modified human female mesh from the open source program, Makehuman. I have removed some of the geometry, such as the eyes and teeth and such, and just started to modify this thing. So, it has only one surface for now and no UV's... since I wanted to make my own thing out of it, I deleted all that.
The selection sets are mirrored, btw... yes, I do know my right from my left. ;)
The problem area is under the boobs. There are other problems, but that's the most pronounced.

JeffrySG
03-15-2008, 04:26 PM
Well, the MH figures are pretty dense meshes, although they look really nice to me. Did you have that pole there in the beginning, or did it get created after you were changing the model?

JeffrySG
03-15-2008, 04:29 PM
Also... I just tried freezing the mesh to see how it would look, and that area doesn't look like it's really pinching the model, maybe it's just an OGL display error? Have you tried to render it in LW to see how the render looks? Might be worth a try if the model is really ok....

jin choung
03-15-2008, 05:13 PM
yah, the triangle is what's causing it.

but look at the mesh - see how the triangle can be turned into a quad? if you add another "triangle piece" above it? then if you get rid of the diagonal, you have a quad.

but then you have another problem don't you - the quad above is now a 5 pt poly....

SO - what you would do is kill the quad that is where you would "add a triangle", then the poly that would become a 5 pt. poly - run BANDSAW through it... you're adding another row of edges through those polys.

now, kill that triangle and you should have a "hole" that is exactly the right fit for two quads.

i know... i know... if you understood the above, i would be amazed.

jin

jin choung
03-15-2008, 05:18 PM
dunno if this attachment is gonna work....

jin

Giacomo99
03-15-2008, 06:16 PM
In my opinion, the model you posted is fine. I wouldn't worry about one or two "poles--" they'll be unnoticeable in the final render.

I would, however, avoid trashing the UV information (as you seem to have done) if you are planning on ever texturing the thing.

Giacomo99
03-15-2008, 06:39 PM
Or, more to the point: rebuilding the model is an excellent exercise in learning how to work with SubPatches. If you're new to the process, though, you're probably not going to achieve a significantly cleaner mesh than the one you posted--the basic MakeHuman mesh is, topologically, pretty close to optimal.

JeffrySG
03-15-2008, 08:48 PM
Or, more to the point: rebuilding the model is an excellent exercise in learning how to work with SubPatches. If you're new to the process, though, you're probably not going to achieve a significantly cleaner mesh than the one you posted--the basic MakeHuman mesh is, topologically, pretty close to optimal.
:agree:

IMI
03-15-2008, 09:05 PM
Thanks for the suggestions, guys. I had to do some Family Time, but now I've been 'allowed' to get back to LightWave...
Jin, I do understand what you're saying, and I had tried some of that sort of thing earlier, but the problem kept moving...up, as you suggested. Although it seems to be the only way of resolving it.
JeffrySG, no, it's not an OGL thing. Modo shows the same effect in the preview render.

Giacomo, I'm sure you're right, but that area is pretty close to what it was from the original OBJ file. I might have pulled something out of place, though. But yeah, it is more or less an exercise. This is how I've been learning how to model humans, plus I wanted something different than some out-of-the-box sales shelf mesh.
As for trashing the UV's, it's simply because I wanted something better, but also to reflect the changes I've made more closely. I'm actually pretty comfortable with making UV maps, so that wasn't a concern.

IMI
03-15-2008, 09:33 PM
It's amazing sometimes what walking away from a problem for a while can do. I managed to fix it, for the most part. I still have a few little creases here and there, but no big deal. Thanks again, jin, I did pretty much what you suggested, and even managed to maintain the curvature.

Surrealist.
03-15-2008, 10:22 PM
Yeah, that's it exactly. Jinn did visually what I was trying to explain. Glad you got it figured out.

For future reference, know that it is simple math. If you have a triangle you either have to add one edge or get rid of one. From there it is a matter or directing the flow so that it is simple and follows the contour of the object.

This is what I was talking about in the beginning of my tutorial. It is a constant trade off.

There is a sliding scale. At the top is the "perfect" mesh. At the bottom is the most economical mesh. The perfect mesh - unattainable - would be all 4 poly points. The most economical (less polys) would be full of 5 poly points, some tris here and there and even an 6 poly point or two.

So the balance is how little polys you can get a way with and still have a smooth mesh. The reverse can also be true. You can have a mesh so dense that it creates bumps, ridges and so on and is too harde to edit.



Rule of thumb:

Always concentrate on the correct poly flow first. This way most problems will take care of themselves.

IMI
03-15-2008, 10:41 PM
I'm beginning to see what you mean, Richard. Thanks again for your help.
This problem here has also given me some ideas for how I can fix that guitar I'm still working on. I don't have that particular problem anywhere, probably mostly because it started as a subpatch and not a polygonal mesh, but in the course of fixing this, I learned some new techniques.

I love this forum. :)

Surrealist.
03-15-2008, 11:02 PM
Me too. :)

Also by the way when I first posted for you to look at my tutorial I had a temporary "disconnect" brain lapse. I forgot you had already been looking at my tutorial. :D

LW_Will
03-15-2008, 11:39 PM
Yeah, Richard, IMI, but, if you look at the mesh, it doesn't really require those "two rows to one row" tris that give you the "star" problems... the 5 poly poles.

If you doubled the rows above the 2-1 polys, the would run the entire model, actually an amazing piece of edge looping, but why would they give to you model with these flaws in it? Maybe its so you can't easily steal the mesh? Maybe so you can see that the model is theirs? I do not know.

I would be interesting to get this model into a "perfect" quad poly model, then try animating with it.

IMI
03-16-2008, 12:29 AM
I don't know either, but I suppose it was designed to work optimally with their own program.
There is no way to "steal" the mesh, though, as it's completely open source and they even say you can alter it, redistribute it and even sell it, as long as you include their copyright notice: (http://www.dedalo-3d.com/legal.php)

MakeHuman© mesh is released under MIT License

Copyright© 2001-2007 makehuman.org

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Mesh"), to deal in the Mesh without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Mesh, and to permit persons to whom the Mesh is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Mesh.

THE MESH IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE MESH OR THE USE OR OTHER DEALINGS IN THE MESH.

JeffrySG
03-16-2008, 12:31 AM
They actually have a PDF file that talks all about the specific mesh that they use. Pretty interesting....

http://www.dedalo-3d.com/docs/2005-12-01-new-model.pdf

IMI
03-16-2008, 12:42 AM
Yes, interesting indeed. Great modeling reference as well.

IMI
03-16-2008, 12:47 AM
Me too. :)

Also by the way when I first posted for you to look at my tutorial I had a temporary "disconnect" brain lapse. I forgot you had already been looking at my tutorial. :D

Oh, I missed this.
Yes, your modeling tutorial is really quite good and has helped me out quite a bit. NT ought to include it with their tutorials.

Surrealist.
03-16-2008, 01:35 AM
Thanks. Well, that would be interesting. I would have to reformat it. Jeff was also asking me to do a video tutorial on it. But I did not really have the time. He wound up doing some pretty good tuts of his own independent findings that also intersect with things I have been saying. I think most people come across these " laws" on their own, eventually.

RTSchramm
03-16-2008, 02:04 AM
Here is how I would fix the problem area under the breasts. Refer to the attached documents. The model you are using is full of problem areas that would show up immediately if you were to attempt to animate it. If you are using Sub-Division modeling for organic objects, the less edge loops required to achieve a particular effect the better or you start to see faint edges where their are too many edge loops too close together.

As you see in the wire frame, I reduced the number of circular edge loops that define the roundness of the breasts. The edge loops were pinching in this area. I could do a lot more to clean up area between the breast to remove the 4 poles, 2 that I created removing the other problem, but I was just working on the area that I believe you were having issues with.

Keep in mind that programs that automate the creation of human models don't really do a good job of creating models that are ready for animation, as you have already discovered. I found that it's usually quicker to load such a model and take screen shots of the model from the TOP, Bottom, left, and front views and then use the screen shots as reference photos. You don't get the perspective distortions like you do when using real photos.

The following web sites may help you understand edge loops:

http://staff.ci.qut.edu.au/~barkerc/Final%20PAN%20website/edgeloop.htm
http://blenderartists.org/forum/showthread.php?t=93651
http://www.subdivisionmodeling.com/forums/showthread.php?t=1545

Oh, and finally, If you don't plan to animate, or move your model, you can do what ever you want as long as you get the result you are looking for.

Hope I was helpful,

Rich

IMI
03-16-2008, 03:20 AM
Yes, Rich, very helpful. Looks good. :)
Animate? No, not likely, although I was planning on making a bone hierarchy for posing for still shots.
But this is mostly just practice, exploring new territory and all that.
I've fixed about as much of the mesh as I plan too, and I've been UV mapping it for the past 5 1/2 hours, since around midnight.
Time for some sleep, I think. Good thing it's Sunday. ;)

Weetos
03-16-2008, 05:39 AM
But this is mostly just practice, exploring new territory and all that.
Oh yeah, see what you mean :hey:

Giacomo99
03-16-2008, 07:23 AM
If you doubled the rows above the 2-1 polys, the would run the entire model, actually an amazing piece of edge looping, but why would they give to you model with these flaws in it?

When modeling with SubPatches, there's always going to be a tradeoff between "correctness--" both topological and anatomical-- and editability.

I think most working professionals would agree that it's better to have a few five-poly corners than for the mesh to be too dense to easily adjust.

IMI
03-16-2008, 09:22 AM
UV mapping going so far so good.
Although...
Most of my UV mapping in the past has been with simpler objects, and even the more complex objects have been less organic. Furniture and gadgets and such.
I've seen some videos and read some books, but mostly I've learned through trial and error.
I'm still not entirely sure if it's more "right" to make many separate UV maps for different parts, or to map the entire object in one map containing everything.

If anyone sees any glaring errors, or has any suggestions, I'm all ears...or eyes, as it were. ;)
This has been "relaxed" as much as possible. It's not perfectly even, I know, but it passes the 3D painting test well enough in Deep paint 3D. I wish there were a way to make all polys the same relative size without hours of point dragging.

I used modo for the initial unwrapping, and refined it in Modeler with the PLG UV tools. An awesome combination. I'm looking forward to seeing what 9.5 brings to us...

IMI
03-16-2008, 09:28 AM
Oh yeah, see what you mean :hey:
:lol:

Nangleator
03-16-2008, 10:27 AM
I wish there were a way to make all polys the same relative size without hours of point dragging.
Yeah, some sort of grid quantize function that wouldn't drop points on top of other points. How hard could that be?

I've just finished watching Taron's head modeling video for the first time. Following him along, I've come to the conclusion that his "extend-collapse" trick is an amazing way to rebuild poly flow and move those pesky stars to flatter areas of the model, where they belong.

If you don't know what I'm talking about, go to the NewTek Training site, look for Siggraph videos and find Taron's bit.

Basically, pick 3 or more polys in a problem area, hit Extender Plus, then Collapse Polygons. You are left with an even number of tris around a point. Go around the circle merging tris into quads. This is probably best done with subpatch mode on. The trick is, you have choices of how to merge these tris, so it's either a matter of rebuilding what you had, or redirecting the poly flow.

IMI
03-16-2008, 11:00 AM
You mean this?
http://www.newtek.com/sigvideos/

Nangleator
03-16-2008, 11:15 AM
That's it. Useful techniques there. The Gnomon video is well worth purchasing. Consider this a teaser.

IMI
03-16-2008, 11:18 AM
Oh, I see. I wasn't aware there was a Gnomon video. I'm definitely going to check that out. Thanks for the info!

RTSchramm
03-16-2008, 12:45 PM
A modeler named Taron has a good video called "The secrets of organic modeling", located on the Gnomon Workshop web site, which shows how to create excellent sub-d head models with the minimum number of edge loops. As an extra bonus, he teaches the course with LW 9.0.

There are two books that I highly recommend for any one who ones to model the female figure:

Edgeloop Character Modeling For 3D Professionals Only by Kelly L. Murdock and Eric Allen:

http://www.amazon.com/s/ref=nb_ss_b/104-0991031-4580760?url=search-alias%3Dstripbooks&field-keywords=Edgeloop+Character+Modeling&x=0&y=0

Virtual Vixens: 3D Character Modeling and Scene Placement by Arndt von Koenigsmarck:

http://www.amazon.com/s/ref=nb_ss_b/104-9537727-0691906?url=search-alias%3Dstripbooks&field-keywords=Virtual+Vixens&x=0&y=0

And finally,t he UV map looks good, except the breast area is still distorted, and I highlighted the problem areas in red, refer to the attached jpg.

You can search the LW forum for advice it where to get some excellent UV plugins also.

Rich

RTSchramm
03-16-2008, 12:53 PM
The Taron video course can be found here:

http://www.thegnomonworkshop.com/dvds/tba01.html

Rich

IMI
03-16-2008, 01:32 PM
Thanks again, Rich.
I just went ahead and ordered that video after reading all up on it. Looks great.

Yes, the stretching of the UV's. Such an incredible nuisance. After I finish mapping the rest of this figure I'm going to search for some more methods of relaxing all that, quantizing, whatever you want to call it.
That could take all day, just manually dragging all those points around til everything is evened up.

RTSchramm
03-16-2008, 02:23 PM
While I new to modeling and such, there was a technique that William Waughn uses that aligns the selected points in either a vertical or horizontal line using the "stretch" tool. This tools works with UV points too.

I attached two images to show how great this works.

You first make sure that the the selection "Mode" is set to "action center:Mouse" Select the point that is at the position you want to move the other points to, in the attached example I marked this point RED, this is your anchor point. Press the "h" key for stretch, and hold the middle mouse while dragging, and you will see the other points align either horizontally, or vertically to the anchor point. Its a really quick way to arrange points in a line.

Rich

IMI
03-16-2008, 05:45 PM
Yes, I had forgotten about that one. (*mental note to self to try to remember it in the future). I usually use Set Value for that sort of thing. But that only works with points along an axis and nothing in between.

I don't know how useful that would be with a UV map with alot of curved lines in it, but it might be able to quicken the process somewhat.

IMI
03-17-2008, 06:25 AM
You first make sure that the the selection "Mode" is set to "action center:Mouse" Select the point that is at the position you want to move the other points to, in the attached example I marked this point RED, this is your anchor point. Press the "h" key for stretch, and hold the middle mouse while dragging, and you will see the other points align either horizontally, or vertically to the anchor point. Its a really quick way to arrange points in a line.


Hey Rich, I wasn't considering the implications of that yesterday, since I was thinking about how to take a circular group of points and even them out. But in the course of doing that it distorts the edges which run through them. This technique you posted is a reeeaaalllll nice way of straightening them back out afterwards.
Thanks again! :)

RTSchramm
03-19-2008, 07:14 PM
No problem. I'm glad that I can help.

Rich