Wierd tessellating material problem

[Olympus1000]

Hi,

I'm having a wierd issue with adding a material to a model. As you can see from the pic, I'm trying to make a clear plastic jug, but the material is coming out all tesselated.

I've made all the normals face in the correct position, but that hasn't solved it. Any clue?

[ekahennequet]

Hi. It's hard to tell from a rendered frame. Do your have "Wire" option checked in the Material? Or, "Force Wireframe" in Render Setup (Renderer tab)? That's what it looks like to me, but I can't be sure. If you could upload a zipped scene file or a screen grab of the scene showing the model's mesh, Material, and Modify panel would be helpful.

[Olympus1000]

Hi, the material isn't wired and displays perfectly on another model, likewise I still get the strange effect with different materials. The model was imported from cad data (I think it was originally created in solidworks), and the normals were all facing the wrong way, but as soon as I started flipping the normals, I started getting this wierd effect.

 

[Steve_Curley]

You may well find that many, if not all, of the vertices are not welded together - they need to be. And don't forget that the inner surface normals have to face inwards, the outer ones outwards. If they're wrong the vertices may not weld correctly.

[ekahennequet]

Hi. Did you flip the normals manually (per poly)? I'm guessing a couple of things that may cause this.

-If your object doesn't have open edges, then try the Unify tool in Editable Mesh's Surface Properties rollout in Polygon mode.

-Your object may not have welded vertices and are randomly flipped. Unify will not work if your polys are detached from each other. Vertices must be welded first.

-Editable Mesh is not great at detecting faulty meshes. If you convert it to Editable Poly, Editable Poly will force your mesh to have Unified normals. If will not allow you to weld opposite facing polys.

In your case, try this:

1. Right-click object in viewport, check Backface Cull so you can see the direction of the normals. Change the viewport display to Shaded.

2. Check for Open Edges by applying STL Check set to Open Edge Errors, Select Edges in Selections, then Check. If you see errors, delete the modifier.

3. In sub-obj vertex mode, weld vertices. Use small threshold amount if necessary.

4. In Surface Properties rollout, choose Unify. You may need to Flip the whole thing afterward depending on which direction the polys are facing.

If you still have problems, please upload a zipped sample file. You can detach a small portion of the model if this is a proprietary object.

[ekahennequet]

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@Steve_Curley wrote:
You may well find that many, if not all, of the vertices are not welded together - they need to be. And don't forget that the inner surface normals have to face inwards, the outer ones outwards. If they're wrong the vertices may not weld correctly.

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Ha. You read my mind, Steve. Exactly what I was thinking. 🙂

[Steve_Curley]

Charged the batteries in my crystal ball 😉

[Olympus1000]

I think you're both right, I've just welded a couple of vertices and already noticed a difference (see pic). Some of the vertices are quite off so I've got a bit of tinkering to do, but it looks like thats what the problem is. 

[ekahennequet]

I would select all vertices and Weld. Then use Unify Normals.

Tip: Keep your viewport in Shaded (F3) + Edges Faces (F4), and turn Backface Cull on in Object Properties. You will have an easier time seeing what's going on with your model.

[Olympus1000]

Bah!! It's not working! I did the STL check, and it came up with around 366 open edges!! I tried welding at a higher threshold (I was previously at 0.1) and that started merging edges too much that it distorted the jug!

I've got a lot of mis-matching verticies, for example below, the vertices at point 1 are fine, but the verticies start to move further and further apart as you move around the lip of the jug (point 2 then point 3). So I'm guessing I need to start moving some vertices, or indeed re-model the whole thing from scratch!

[Steve_Curley]

I was originally going to suggest exactly that - for the jug itself it should take no more than a couple of minutes. The Handle however will be more problematic. To fix what you have you'll need to line up the vertices - but that will only work if you have the same number of them and it looks to me like the gap (between vertices) on one side is smaller which implies that the 2 parts actually have different numbers of vertices. That's going to be a pain to fix.

[Olympus1000 · Accepted solution]

In the end, I created a new jug (lathed a line), then just moved the clip to the new jug (it's relatively out of view so I can get away with a couple of missed poly's). Thanks for the help!