![]() ![]() The most common problem is an edge connected to more or less than two faces. Non-manifold meshes aren’t always obvious, but it’s often easy to see that something about the geometry is wrong. But I still don’t know what a non-manifold mesh is! That doesn’t mean non-manifolds are always terrible, but if you are modeling for something other than rendering you will want to fix them. Thickness is also needed to have volume, every object we print must have an internal volume. Even the thinnest piece of paper has some thickness. We can’t print floating vertices or walls with no thickness. Remember how our universe is 2‑manifold? Non-manifold geometry can’t exist in reality. The biggest issue, and probably why you are reading this, is 3D printing. ![]() Without a continuous surface, a mesh can’t encompass a closed volume and have an inside. They need meshes that have a clear separation between inside and outside, which Non-manifolds can’t give. On the other hand, Manifold meshes are an absolute requirement for fluid simulations. Other software and algorithms may not take non-manifolds so kindly, though. This has improved by leaps and bounds with Blender 2.80, so it’s not much of a problem anymore. Having islands in the UV Map for continuous geometry is a recipe for a headache.īoolean operations can give you trouble too. For one, they can’t be unwrapped without splitting the mesh. If you are interested in the hardcore stuff, check out the Wikipedia page for manifold. Since we are building 3D shapes from 2D shapes, we can cut them and unfold them into planes in 2D space.ĭisclaimer: I’m not a math guy, so I’ve tried to avoid lingo and keep it focused on 3D. Life being 2‑manifold is what allowed techniques like UV unwrapping to work for CGI. Our entire universe and every object we will ever hold are 2‑manifolds. These concepts don’t apply only to computer graphics. Wait, 2? Remember we use 2D polygons to build 3D shapes, therefore meshes are 2‑manifolds. But we only care about 3D, so let’s stick to 2‑manifolds. Manifold space can have any number of dimensions and it gets weird real fast. STL file Unfold 3D mesh to be a 2D mesh Export the 2D mesh to. Yep, the good old plane is a non-manifold, who would’ve guessed? This software can unfold a 3D mesh to be a 2D mesh. ![]() Cubes, Spheres, Torus are examples of manifold objects while a plane is an example of a non-manifold since it’s not continuous. They wrap without any end or beginning. The second feature of manifold objects is that they are continuous. ![]()
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