View Full Version : Can anyone help me figure out what is wrong with this mesh?

01-04-2019, 05:06 PM
I'm trying to get used to lw 2018 and doing my first project in it. I noticed these little render errors on this object, and took out all the details except this single mesh. It renders glitches on it when sub patched. When subpatched in modeler it even seems to glitch, the lines flash as you rotate it around. I exported it to a .obj file and then imported it to see if I could fix any sort of normal error which has helped with funky objects in the past, but it didn't fix this.

I can't figure out why this object file is glitchy. I build it from scratch and with a blank standard or principled shader it renders errors on it.


01-04-2019, 05:20 PM
Seems like you have some odd edge weighting that might be causing side effects, and some non-planar patches as well that might be causing issues.

Maybe try freezing the SDS to geometry, select any non-planar polys using stats panel, and just triangulate those to see if that fixes your issue?

01-04-2019, 05:29 PM
Could be a few things; smoothing error, extra junk geometry sitting in the same location as your good geo, n-gons / missing supporting edges, non-planer polys. The statistics panel should help trouble shoot a few of those. You can also select a poly in that area, and make it invisible, then see if there is anything underneath it. Also if your surface is double sided, try turning that off. Next time include a wireframe image, so we have more to go on. Hope that helps.

01-04-2019, 05:55 PM
Hey guys thanks for getting back to me. I attached the obj file in case anyone had time to open it and see if they also get the error. I did check the mesh for bad geometry and the like but didn't find any. So I decided to just scrap the mesh and make a sphere with flattened front (to see if it had a harder time on flat faces) It has the same issue. I think the problem stems from being a small object fairly far away from the origin. It's only a few mm wide, and a meter or so away from the origin. So maybe it's a positional issue at that fine of position?

I'm attaching two screen shots. Same object. One is 2m from origin, the other is right at the origin.

01-04-2019, 05:58 PM
Open Polygon Statistics.
Check if you have 1-2 point polygons.
Delete them, if any.

Normal route of cleaning up mesh is:
- merge points,
- unify polys,
- delete 1-2 point polygons,
- eventually triangulate n-gons, or remake them to triangles and quads.

01-04-2019, 05:59 PM
Thanks Sensei, there was no 1-2 point polygons or other issues. I also created a new mesh (just sphere with some points scaled flat) and it has issues. So I can't imagine how this is a geometry issue.

Attaching object and scene file. Switch between the cameras and you can see the object further from the origin is staring to fracture. It's the same object just copied and moved on the same layer.

Is there a way to increase the positional accuracy of LW? This is LW 2018.0.7

01-04-2019, 06:53 PM
Hello 4dArtist.

I had a quick look...

Your object is teeny weeny, but you have another copy of it 2m away on the same layer?
If you do a merge points set at 0.5mm it will sort out your problem.

Edit : scrub the merge point it doesn't do anything.

Google teapot in a stadium... I think that's your problem.

Right! Had another look at it. If you set your surface to double sided then it's ok and if you change your background to pink the render errors are now pink.

01-04-2019, 07:23 PM
Hey Swampy. Ya it's definitely the scale. I guess lightwave gets less accurate further from the origin of the object file (not scene origin). It's odd because we aren't talking stupid crazy numbers here, This is a 10mm object, 1m away from the origin.

I put in a bug report for what it's worth.

01-04-2019, 11:16 PM
In 2018.0.6 Cam1 and Cam2 render look good here - no strange artifacts (can't open the lwo but the lws loads fine).

Maybe changing the "Polygon Intersection Mode" in "[Render Properites] -> [Render]" helps in LW 2018.0.7 ?

01-05-2019, 03:00 AM
Yeah I've had this issue a lot. It got fixed in beta, then came back, it Must be a very fine issue to fix. Change your polygon intersection mode to double precision (Or watertight, if it's on fastest). It's related to ray accuracy issues, and nothing yo do with your mesh. It drove me mad, rebuilding parts if my mesh several times!