If you want details (and rather excitingly they have profound philosophical consequences for the ultimate nature of reality and what happens in the quantum structure of the universe itself), I've written a separate page on the question. The problem is caused by a nice distinction that mathematicians make between open and closed sets, and the impossibility of representing this distinction unambiguously in a finite computer. Things will get worse more quickly if you create such objects using curved surfaces rather than simpler flat planes. In particular you may find it impossible to do further boolean operations with it, and impossible to write it out as an STL file. Such an object cannot exist in the real world of matter, and so your design will start to unravel from this point onwards. A non-manifold shape is one that, for example, has a face on it of no thickness. Eventually you will discover if you keep doing this that AoI ends up thinking it has what is technically called a non-manifold shape. But this is a boolean operation on a coincident surface - the flat face where the red and blue blocks just touch. It is also the most important hint in the list, for reasons that will become apparent.Īnd to form their boolean union to make the shape you want. You have to get into a way of thinking with AoI, and this hint has the biggest influence on how you think about constructing shapes. Hint: avoid doing booleans on coincident surfaces Open the transform dialog and set all scale factors to 25.4 (Mesh->Transform)Ģ.Select all the vertices in the model (Edit->Select All).Open the object in the mesh editor (Object->Edit Object).Convert the object to a mesh if it isn't already (Object->Convert to Triangle Mesh).If you're working with an existing model that is scaled one inch per unit, you can convert it to millimetres using the mesh editor: Millimetres are strongly recommended for RepRap work. Your design will then be in millimetres, but can be worked on in inches. If you're from a place which has not yet discarded the archaic unit of "inches", a quick cheat is to set the grid spacing to 25.4 units, and the divisions per grid unit to represent the fractions of an inch that you wish to deal with. Treat one AoI unit as one mm, and experiment by building objects of about the size that you want to end up making. I am assuming that you will be working in millimeters as the standard engineering unit. However, do make sure you explore and get familiar with Boolean Modelling (in the AoI "Tools" dropdown) and the use of the grid (under the "Scene" dropdown). It's important to learn without the added pressure of having to solve a specific design problem too. If you are going to use AoI for CAD (for RepRap or for any other engineering) start by getting familiar with it using its own documentation and examples don't begin by trying to design an entire mobile phone casing (or whatever you actually need) first off. Note that on some systems you may need to be the superuser or administrator to do this, as it will install a file on your machine. Once you have installed it, go to the Scripts and Plugins manager (in the AoI "Tools" dropdown) and get all the scripts and plugins from the web (you won't use all of them, but they're quick to download, and this is simpler than deciding which you want and which you don't). The AoI website has detailed instructions for downloading AoI and getting it working under a wide range of operating systems. However, we have found a number of how-to hints that help when using AoI for mechanical design, and those are documented here. There is a lot of good clear documentation that comes with AoI, and it is not the intention of this page to duplicate any of that. AoI was written by Peter Eastman and others and is completely free and open-source. However, it has an extraodinarily minimal, wide-spanning and intuitive user interface that is very easy to learn, and it has the ability to output solids as STL files STL is the standard format for rapid-prototyped parts. AoI is not intended as an engineering computer-aided design (CAD) tool, but rather as a three-dimensional design system for animated computer graphics. We have decided to use Art of Illusion ( AoI for short) as the design system for RepRap. Hints on Using Art of Illusion for RepRap 0.
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