Importing CAD Models into Cinema 4D: Common Issues with CAD Files

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Instructor Rod Ross

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In this video we will discuss problems and give examples we run into when importing CAD models like topology and UV’s.

In this video we show an example of a CAD model and and discuss issues like topology and UV’s. We will discuss how this can cause difficulties painting and texturing models and possible problems with rendering.



- In this tutorial, we're going to take a look at common issues with CAD files. Here, I have an example of a typical file that's been exported from a CAD file and imported into Cinema 4D. Then, I have a poly model that's been modeled in Cinema 4D. So let's take a look at some of the common issues with CAD files, and the first one is opening the file. If a client gives you a CAD file, you may not have access to a program that can open it and the client may not either. There are many different CAD programs out there and many different file types, so just opening the file can be a big problem. Our next issue is a CAD file that needs repaired or edited. Sometimes you may receive a file that has a broken piece or will not export correctly, and most of the time the easiest way to repair a CAD model is in the same program that it was made in or another CAD program. So you may find yourself replacing polygons, rebuilding a section of an object, or recreating the object completely. Another common issue is problems with exported CAD files, and the first one is unwelded points. I'll show you what that is. I'll zoom up on this CAD model. Then, I'll go to Point mode and I'll click on this point, and if I drag it up you can see that it's not connected. That's an unwelded point. So I'll zoom back out and deselect this. The next one is topology. You can see on this CAD model, we have large triangular shapes mixed with quads, and this type of topology can cause problems with animating, texturing, and rendering. The next issue is phong issues, and I'll zoom up on the model to show you this. I'll click on it, and then I'll go to Mesh, Commands, and Optimize and I'll click on the options. I'll just leave this at 0.01. I'll say OK. Now that our model has been optimized, you can see these dark shaded areas, and those are phong issues. Normally, we can fix those by going to the Phong tag and I'll just put in a smaller number here. We'll try 22, and that fixed our phong issue. To fix phong issues, I would normally try a number under 45 and after that it's somewhat trial and error. The next problem that we have is missing polygons. I didn't see any on this model, but sometimes when they're exported, especially in areas like fillets, you can get missing polygons. The next issue that we can have with CAD models is setting up UVs. As you look at the topology and see what a mess this is, you can see how setting up your UVs would be more difficult, especially on more complex objects. Which brings us to our next issue, which is texturing. Difficulty getting good UVs can also cause texturing problems. The next is animating, and I'll just zoom out here. Just to give you an example, I'll put a deformer on this CAD model. So I'll go to my deformers, I'll hold my Shift key down, and I'll choose the Bend Deformer. If I go to Bend and dial up the strength, you can see how this CAD model starts falling apart and that's because of the topology. Now, if I take this same Bend Deformer and move it under my poly model, and I'll turn this off and drag it over, and then turn it back on, you can see how much nicer this deforms. I'll just get rid of this. Also, by looking at the topology on this poly model, you can see that setting up your UVs would be much easier. Now that we've covered some common issues with CAD files, let's take a look at what we'll cover in this tutorial series. First, we'll take a look at the file types that Cinema 4D will open, and then we'll take a look at several different programs that can open up a wide variety of CAD files and export them, so we can open them up in Cinema 4D. Then, we'll take a look at the Mesh Checker in Cinema 4D. This will help us identify problems with our CAD files so we can fix them. Then, we'll cover exporting our CAD file to a mesh so that we can open it in Cinema 4D. Next, we'll look at ZRemesher and UV Master in ZBrush. ZRemesher is a quick way to retopologize your objects in ZBrush, and UV Master is a quick way to set up our UVs. These will help us solve some of the common issues we run into with CAD files.
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