Surface Area of a Projection

How to measure surface area of projection of a solid on any plane? Particularly useful, when we get to deal with flows.

For some time now, the issue’s been simpler since the Silhouette operation appeared in the GSD :

The outcome of that operation (under certain configuration), on the previously described rotor, is a ready-made surface :


on which we can quickly execute a measurement of the surface area:

Right, but in the past that option didn’t exist, and we had to manage without it. Hence, we can call that an old school method, basically, it’s about making projection of a file in the .stl format on a plane, or more precisely, its CATIAtic tessellation. What we need for that is, the Digitized Shape Editor – in which we need to use the following tool :

Having created a Mesh of the projection later on, this results in a direct measurement of the surface area :

As we can see, that’s not the optimal method – because we would have to focus on repairing the Mesh – which means, we would get some kind of approximate measurement, precise to the same extent, as precisely designed was the Mesh…

But what makes that method better than the Silhouette method from GSD? Using this method, we can measure surface area of the whole product projected on any plane. But we need to use a different format for saving the product to file, one that would be possible to read by DSE, because the product can’t be saved as .stl… For that, I used a very underestimated format, the .3dxml (underestimated due to a variety of reasons :-)), and that resulted in :

By figuring out further, we can make AllCATPart or Associated Part from the product and use Silhouette, can’t we…? But first, we would have to combine all the bodies into one, and those of you, who’d been doing that with large compounds know, that sometimes it’s impossible, especially, when there are contacting shapes called to the n-th power… (e.g., “small tangent elements”, “impossible situation”).

Hence the old school method tolerates such imperfections…

And now, I’ll atypically begin from an introduction being a conclusion at the same time… Some time ago, I had a task to mark out the whole outer contour of a machine, in order to make a model (laser burned). And hence, the idea to make the projection of the whole machine on a plane in DSE. By carrying on with that method, I reached the same point as the one on the above image of a crank-piston system, i.e., I got tessellation projected on a plane. So what, success? Well in fact, no, because any attempts to create figures out of such tessellation would result in a projection of thousands of little triangles – nonsense… Instead, we should create surfaces from that flat tessellation and extract the outer contour (boundary), which we should pass on to the documentation, and get “.dxf” ready to be burned. Just as coffee likes cigarette, DSE loves Quick Surface Reconstruction module, which has an Automatic Surface tool. I took it for granted, I assumed it would be a quick job – and that’s where I got my lesson of humbleness, never be too sure of something before you can break your teeth on it… The projection of flat tessellation in the Automatic Surface tool resulted in :

So far I haven’t found a way to bypass that, to make Automatic Surface work on flat tessellation. It probably needs manually marking out the contour based on that projection. The time drew nigh, so the machine image got edited, and everything except the outer contour was removed manually, line by line…
























Comments: Be first

Recent Posts

I welcome everyone interested in CATIA . I will […]

Each Part in CATIA has its own UUID identification. It’s […]

The matter might seems trivial… it gets a bit […]

In the previous entry, I have described some of […]

And now an entry for Fetishistic B-Rep Dodgers 🙂 […]