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Thread: Sub-Patch-Pinch...why and how to fix?

  1. #1
    Pancakes! IMI's Avatar
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    Sub-Patch-Pinch...why and how to fix?

    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.
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  2. #2
    Space Monkey 3DGFXStudios's Avatar
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    Remove 3point polys if its possible or welt it later where the tension is lower

  3. #3
    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.
    Last edited by Surrealist.; 03-15-2008 at 11:33 AM.

  4. #4
    Pancakes! IMI's Avatar
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    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.

  5. #5
    Fórum áss clówn Hopper's Avatar
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    Well?

    C'mon man .. it's been almost 2 minutes.
    Playing guitar is an endless process of running out of fingers.

  6. #6
    Pancakes! IMI's Avatar
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    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.

  7. #7
    Pixel and Poly Pusher JeffrySG's Avatar
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    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).

  8. #8
    Pancakes! IMI's Avatar
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    Quote Originally Posted by JeffrySG
    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....
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  9. #9
    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.

  10. #10
    Pancakes! IMI's Avatar
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    Quote Originally Posted by Giacomo99
    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.

  11. #11
    Pixel and Poly Pusher JeffrySG's Avatar
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    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.

  12. #12
    Pancakes! IMI's Avatar
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    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.
    Attached Files Attached Files

  13. #13
    Pixel and Poly Pusher JeffrySG's Avatar
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    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?

  14. #14
    Pixel and Poly Pusher JeffrySG's Avatar
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    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....

  15. #15
    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

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