I’m using the Solidify modifier to create the thickness of some leather boots, and discovered that using the Vertex Group option creates some truly ugly rendering artifacts:
When Solidify is applied to only the Vertex Group specified, the rest of the mesh renders with splotches all over it that resemble the effect of duplicate coincident surfaces, but there are none such in this model, as the other renderings show.
Has this been reported before? It seems the kind of thing that would be found pretty quick, but a search turned up nothing similar. If there’s a remedy I’d appreciate the info. I don’t have to use the Vertex Group option, but it just seems more efficient to do so, and if it’s an option, it should work properly
I’ve boiled this problem down to a very simple .blend (attached) that shows the problem quite clearly, but still have no idea what’s causing the rendering error. Changing none of the modifier specs (other than not using the vertex group) seems to have any effect, and it happens with all type of materials. If no one can figure what’s going on I’ll submit this as a bug.
The vertex group is causing non-manifold geometry and is likely the root of the problem. It’s best just to apply the thickness to the whole mesh or apply the modifier and clean up the problem area inside.
I know the using the Solidify:Vertex Group option causes the problem, just not why, nor how to fix it (if it can be fixed). Can’t always apply the thickness to the entire mesh as this causes problems with more complex models, such as parts of the costume I use on my Neziņa character. Applying the modifier also doesn’t cut it because a mesh with Cloth specs or under Armature control will show mesh interpenetration that the Solidify modifier is designed to circumvent.
If the vertex group is an option but causes non-manifold geometry, then I call that a bug.
I agree. It looks like a bug. Can’t hurt to report it.
It looks like the new faces created by the solidify are on top of the faces it should have replaced. That is causing those splotches. just a guess though…
According to the response on the bug tracker, the problem is caused by the Solidify modifier actually creating duplicate faces for the entire mesh, even when the Vertex Group option is in effect. Those vertices with zero weight are not displaced to form the thickness, thus creating coincident faces, which is what I thought this looked like from the get-go.
A possible workaround depending on the model is to use a low vertex weight for vertices where you don’t want thickness, or best not much, since the weight does affect the thickness generated. The nominal thickness spec’d in the modifier is what is generated for vertex weight = 1.0
Some quantitative results that might be helpful if you run into this in your own renderings:
For a model at world scale 1 BU = 1m (the optimum for Cloth physics), on a mesh with nominal Solidify thickness of .002 (2mm), using a vertex group weight of 0.2 to 0.25 seems to eliminate the rendering artifacts without causing egregious problems in other parts of the mesh where it would be better not to have the Solidify at all.
A good idea if planning to use Solidify is to design & build your mesh & it’s topology with that in mind, and thus avoid having the modifier-generated faces pop through the actual faces. This is why I wanted to restrict the Solidify effect, but I may have to re-think some aspects of the mesh instead.
EDIT: Apparently after 2.59 (I suppose that means builds newer than the BF 2.59 release build) there is now a “Factor” parameter in the Solidify modifier that can be set to remedy the coincident face issue, though faces are still generated for the entire mesh.
