The Shapeways Blog: 3D Printing News & Innovation
Shapeways Blog
Tuesday, December 8. 2009
A Rapid Prototyping and .STL Informative Guide
InstaTuts have published a guide for exporting a model from 3DS Max and printing it in ABS plastic (our 'Grey Robust' material - we no longer offer 'Cream robust'). The article contains some useful pointers for the use of 3DSMax’s STL Check Modifier and STL export function (note: Shapeways supports the more compact Binary STL file format, too!)
I found it interesting that the article refers to manifoldness as 'the Vertex to Vertex Rule':What this means is that each triangle of the mesh must share 2 vertices with its adjacent triangles. For example one triangles vertex cannot lie on the side of a triangle, it must be attached to another vertex of the triangle.
There's an image in the article that illustrates this. What do you think? Is this a clear/better explanation?
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I want an explanation of why, any Manifold export would become non-manifold, and why 9 out of 10 programs will say Manifold, but never will all programs agree and say, yup it's manifold.
If an exporter turns a manifold object into a non-manifold object, then that sounds like a buggy exporter. Do you have an example?
Not sure about the other issue, but it could depend on the tool's definition of manifold. Here at Shapeways we need objects that are 2-manifold, meaning that each edge is shared by exactly 2 faces.
Not sure about the other issue, but it could depend on the tool's definition of manifold. Here at Shapeways we need objects that are 2-manifold, meaning that each edge is shared by exactly 2 faces.
I like your definition better, Bart ("each edge is shared by exactly 2 faces"). Note in their example (Figure 1), the object is not 2-manifold even though it satisfies their vertex to vertex rule. There are four edges that have only one associated face.
I suppose the issue is the different definitions of manifold. I've had some models that I can't do much of anything to get them to upload, and others go up with out a problem. and sometimes just using different scales has worked to make it acceptable.
Yes! Size is definitely an issue that can occur when you use 'meters' as the size unit. In some cases you may run into the limited internal accuracy of the software that you use. Vertices are then 'welded' together and this can result in non-manifold meshes. I always use millimeters as the size unit to avoid this.
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