One of the things I’ve been eager to do with my shifting focus is to make certain aspects of 3D modeling more accessible to modelers. Including, for starters, me.

In my experience, there are a ton of tutorials and step-by-steps out there, but so many of them are aimed at animators, or video game designers, or other concerns that don’t necessarily overlap with what I need from an application.

There’s also the reality that each app is its own world. Fusion is nothing like Blender is nothing like Rhino is nothing like Plasticity, and so on. Each has its own internal logic, and just because you more or less understand one, doesn’t mean you’ll understand the others. They’re also so feature-dense that understanding not only what everything is, but how to use it, is and endless task of discovery.

I have a pretty good handle on Fusion these days. But with Blender, I still feel like doing anything requires memorizing some carefully guarded incantation. Doesn’t help that there are approximately 13 million keyboard shortcuts.

But…as I learn my way around these, I’m planning to pass that learning on and hopefully bend the learning curve for others.

Size does matter

This particular problem starts in Fusion. When you something out of Fusion to an STL, the default export options will turn your smooth curves into faceted, many-sided polygons that show up in your 3D prints.

For example, here’s a 1/48 LAU-131 in Fusion:

And here’s the exported STL in Lychee:

To get around this, I’ve been pushing the export settings to 11. And that works. The problem is that it leads to some prohibitively large file sizes. Large like…a single 1/35 track link being 500MB.

You try copying a couple of those out to batch print, and all of the sudden you’re looking at a file that’s measured in gigs, and that chokes out whatever app you try to open it with.

While a somewhat less extreme example, let’s take a look at this 1/32 TBD Devastator instrument panel. Saved out of Fusion, it’s already nearly 200MB:

Looking at the Blender statistics, it’s easy to see why. This relatively simple piece has a whopping 3.7 MILLION TRIANGLES.

This is all a long-winded way to get to the problem. In order to get acceptable-quality STLs out of Fusion, I have to contend with huge file sizes.

Enter decimation

When I think of decimation, I think of the Roman legions.

This isn’t that.

Blender has these things called modifiers that you can apply to objects to, uh, modify them. And they do pretty much anything. You can assign materials, make things act like fabric, make copies of things, combine things, shrinkwrap things, and so on. Every time I play with these I feel like a dog trying to use a computer.

One of the modifiers is Decimate. And what it does is decimate the number of triangles in an object. Which in turn, decreases the file size.

The ratio starts at 1.0, and you can take it down pretty much as far as you want. I’ve found for most things, I can dip all the way to 0.05 without making any real difference to the appearance.

What does 0.05 mean? Basically that you’re removing 95% of the triangles in the object, and collapsing down to just the remaining 5%.

Look at that. The 3.7 million-triangle panel is now a far more manageable 189,000. And the file size dropped from 189MB to just 9.5MB.

You can see similar results from these 55-gallon plastic barrels in various scales. Most of them dropped to a tenth their original size after going through decimation. And a lot of the supported ones that don’t seem like they dropped all that much? That’s because those supported files now include multiples of the barrel.

I’m sure there’s some much more elegant way to do this. If nothing else, with geometry nodes in Blender. But for now, I’m just happy that I have a way to get to high-quality STLs at reasonable file sizes.