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Thread: Help - Holes in my geometry? Bad Render?

  1. #1

    Help - Holes in my geometry? Bad Render?

    Howdy from Phoenix!

    I've been working on an asteroid I need for a show I am working on, and every iteration seems to have the same problem, and I can't find the solution.

    I have started with the Ball Tool and created Globes or Tessellation shares as my base, that I have subdivided as Smooth or Metaform Polygons...
    SubPatch has been toggled on and off, I have used displacement maps and bump maps and every time, I get these errors in my renders.

    Sometimes I get triangular shadows if ray traced, as well.

    A render should be attached to this post. Does anyone have a suggestion?

    Thanks in advance!

    Ben Avechuco
    An on and off lightwave user since 1992 or so.

    Click image for larger version. 

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  2. #2
    Frequenter
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    Hi Avebeno, a bit hard to tell from only that one render but to me it appears as if there are overlapping polygons rather than holes... Is there a chance that you accidently somehow doubled your mesh in the process?!?
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    lorenz

  3. #3
    Registered User
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    Quote Originally Posted by fishhead View Post
    Hi Avebeno, a bit hard to tell from only that one render but to me it appears as if there are overlapping polygons rather than holes... Is there a chance that you accidently somehow doubled your mesh in the process?!?
    Damnit, he beat me to it. Another thing is... at times (not always) spheres as metaforms has caused me issues. It's always best to start with a box and metaform that (and work with quads... not triangles until you freeze it).

  4. #4
    Lorenz,
    Thanks for you reply.

    No, I don't see how I could have. I start with a sphere and use the Magnet Tool to shift some points on the model.

    - - - Updated - - -

    Hmmm. I shall give that a try. Thank you!

  5. #5
    Howdy Ho!
    That's duplicated geometry in my opinion.

  6. #6
    What if you click on Unify Polys button in modeler? Or zoom in on the geo and see if there are almost overlapping polys? Or there could be more than one geo layer in Layout?

  7. #7
    Something similar to this also happens if your "Ray Precision" is too high in the render settings.Click image for larger version. 

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    Last edited by Danner; 01-16-2017 at 08:37 AM.

  8. #8
    Super Member Paul_Boland's Avatar
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    Have you applied Jitter to non-triangular polygons? If so, that could be the problem. I experienced something similar in my early days of working with and learning Lightwave. The solution, Triple the model so all polygons are three point polygons. See if that helps. Triple is under the Multiply tab in Modeler.
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  9. #9
    For the holes, do they typically appear near quads or triangles? If quads, I usually see this behavior when a quad is not smooth and the surface angle is too large for the render engine to smooth out properly. What I usually do in these circumstances is convert everything to triangles (ala Paul_Boland) in a test object (Or at least the affected area) and then do a quick render test using the modified triangle-only object. That at least tells me whether it is a geometry issue. You could also select the polygons around these holes and then Smooth out the geometry as a test.

    Now, you also indicate that you've toggled SubPatching on/off. I also see similar render abnormalities when an object has a combination of regular polygons and sub-patched polygons. This is normally a mistake and happens to me when I don't make sure I have all of the sub-patched polys selected when toggling on/off. So maybe there could be sub-patched polys at the holes that are connected to normal polys. Just a thought.

    The stripes on some of the polys indicate overlapping geometry as others have stated. For overlapping geometry (in general), try hitting M in modeler to merge points. If no points are merged, then overlapping geometry is caused by two polys attached to the same point, facing opposite directions. If points are merged, then it most likely could be two objects occupying the same 3D space with their polygons pointing in opposite directions (think Copy object, flip normal, Paste object). Merging and Unifying Normals usually resolves this. But this is just my two cents!

  10. #10
    TrueArt Support
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    Help - Holes in my geometry? Bad Render?
    I don't think so what you see are "holes". Try changing color of shadow in Light Properties (or Backdrop color in environment settings)
    If color of these "holes" will change accordingly to Shadow Color that you just changed, it will confirm that they are really shadows.


    In Object Properties > Render,
    there is option Shadow Offset.
    Did you try to adjust it slightly?
    Last edited by Sensei; 01-16-2017 at 07:39 PM.

  11. #11
    Axes grinder- Dongle #99
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    Just to settle our minds, run MERGE POINTS followed by UNIFY (POLYS).

    LW default spheres have triangles at the poles, and are non-optimum candidates for subd. Try to use "Quad Spheres" instead, google them. You'll need a Legacy plugin supplied by LWG to use the Quad Spheres plugin. (Basically, it's a cube w/SPHERIFY run on it.)

    IIRC you can sometimes quelle render errors with different smoothing parameters in the Surface panel.
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  12. #12
    Super Member Snosrap's Avatar
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    I'm with Sensei on this. Try some different light types with and without shadows turned on.

  13. #13
    Super Member spherical's Avatar
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    Quote Originally Posted by jeric_synergy View Post
    Just to settle our minds, run MERGE POINTS followed by UNIFY (POLYS).
    That'll clear exactly duplicated/flipped geo, but not overlapping polys. As a debugging step, try turning off Self Shadow in Object Properties and see what changes.
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  14. #14
    Here is what I found:

    With Self Shadow OFF, but Cast Shadow, and Receive Shadow ON... The dark spots still appear.

    With Receive Shadow, no dark spots appear.

    It seems they are shadows. If I make the shadow color RED, the dark spots are RED.

    I tired a Directional Light with Raytrace on, and Spotlight with a shadow map as well.

    I did a version with triangulated geometry.

    I made sure to "MERGE POINTS followed by UNIFY (POLYS)" with no change. It was reported that no points were eliminated, and no Polys has been eliminated.

  15. #15
    Though I would like to figure out what is wrong, I made an alternate asteroid that is working for now.

    I started with a simple sphere with no modifications in modeler, and added some displacement maps in the object "Deform" tab.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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