The Importance of being Hollow

Let me start this with a bit of random trivia. A viagra knock-off company in India has generated 9 hits on my blog this week. Maybe they enjoy 3d modeling?

Anywho, as the title says, it's very important to be hollow. At least if you're a 3d model. See, all 3d printing companies charge per cubic centimeter of material that your model contains. This means that models can start to cost a lot of money. How much? Frosted Detail (FD) runs $2.39 US per cubic centimeter. If you wanted a high quality 16mm die, that would be 1.6cm^3 * $2.39 or $15.66 per die! Yikes!

To decrease this cost, we hollow out our objects so that they use less material. Generally this does not effect the component, since it's either too small to be effected, or meant for a prototype and will never be used.

*SAGE ADVICE* If you are planning on creating masters for mold making, you will want to be -VERY- wary of hollowing your models. Many mold making processes involve a lot of pressure and heat, and will result in a broken master and ruin mold if the model is too weak. Generally speaking, I advise anyone who plans on 3d printing masters to either use wax for bronze casting or make certain that your prints will be very solid, even if they do cost much more.

Alright, so lets look at the quick and dirty method of hollowing out an object. First open up the object you want to hollow out. In my case, it is a very fancy looking box magazine.

An important thing to keep in mind is structural integrity, both as a requirement for printing and for functionality. In the case of my magazine, it is going to be printed in Frosted Ultra Detail (FUD), which has a minimum wall thickness of .5mm (half a millimeter). In addition, it is meant as an accessory to a machine gun, so it must be able to lock into the machine gun's magazine well without breaking. This means I have to be careful about the guides I design to fit it in place:



First I'm going to copy the magazine by selecting the Move tool (or M) and pushing the ctrl key once:



Because I don't want to weaken the magazine guides, I'm going to remove them from the copy:



Now that it's cleaned up, I can scale it down, say, 15% using the Scale tool. To scale it exactly 15%, use the scale tool as normal, but type .85 in for the scale amount. If your remember math class from all those years ago, it means you are reducing a number TO 15% of it's original (or reducing it by 15%):



Now for the tricky part. we need to move the smaller magazine so that it is in the exact center of the original. We can do this by creating some center guides. But keep in mind that the smaller version won't light up exactly with the larger one, but we can still find a good fit by using the guides:



Now, hide part of the large magazine by selecting half of it, right clicking, and selecting Hide from the option menu. This will allow us to move the smaller magazine into place:



Remember your minimum material thickness, and measure to be certain. If you believe some areas may be too thin, just scale down the model by 5%. Once everything looks good, select the entire model, right click on it, and select Reverse Faces from the menu. This will make the distinction between the inner and outer walls:



Almost there!

Now Select both models by drag selecting. Right click them and select Explode from the option menu. This will break both of them out of the component state, and allow them to be recombined as a single model:



And that is the cheap and easy way to hollow out a model. You can actually hollow very complex models in a similar way. However, not all models can be hollowed using this method, but I'll cover that in another blog post.

Until then, thanks for reading!

Modeling Update

I know I said I would make a tutorial for creating round models. However, I've run into a few problems with the project I am currently working on, and though I would share some cliff notes on it.

I noticed a bit of a size problem with my boltguns. Mainly, they're taller than marines with the combi-attachment. Now, I wanted them larger, but not quite that large, so I'm in the process of shrinking them. Here are some of my thoughts and photos to detail the changes:

The bolter was shortened substantially. The flamer was also shortened, including the gas lines. The promethium canister was in the way of the marine's hand, so I angled it downwards.




The melta-gun had its receiver shortened and the fuel canister moved back a bit. This was the second most annoying move, and the receiver didn't cut evenly, but now I know how to cut it very quickly and efficiently. I'll definitely be putting that in a future post.



My last work is the plasma gun, but it is the most difficult because of all the angles. It is still not quite finished and needs polishing. It also remains the largest of the combi-weapons. It should be, however, as it is generally the most expensive, and the only combi-weapon that can shoot twice according to the rules.



Stay tuned for more!

First Post

Ah, so here we go, a blog. Where to begin? Maybe I should start with my intentions.

Keep in mind, I am not an artist, not in the least sense of the word. I make horrible stick figures and scraped by my high school drawing class with a D+. But, I was rather taken recently by the prospect of 3d modelling. Interestingly enough, 3d modelling is not a normal medium like oil or charcoal. No, it is its own, unique form of art.

Those of you interested in it might rejoice in the fact that it does not require great artistic talent to master. At least, not that I have seen so far.

Also let it be known that I have taken no classes or made any studies in the field of 3d art or animation. Everything in this blog will be from my own trial and error, and perhaps, a way for you to avoid the same pitfalls. I do not assume to be a master, expert, or even journeyman in such things. But maybe that is for the better. There are more students than teachers, and there is something to be said for group learning.

As a brief history: I started playing with Google Sketchup (v8) in mid-December. My objective - to design a 6mm scale tank (roughly the size of a quarter)for 3d printing by a company called Shapeways. After a few hours of trial and error, I had something that looked like a tank:



I promptly uploaded it to Shapeways, where their automated system promptly laughed me off the internet. See, it's not enough to simply make a 3d model. Printers are very expectant machines. They expect to know where to begin and where to stop. What is on the outside, and what is on the inside. Where one object begins and another ends.

Being only vaguely aware of such things, I started googling anything and everything I could about 3d printing. Finally, I figured out exactly how the model should be put together. But I didn't feel like continuing on my tank yet. I felt I needed to start smaller, with a basic structure that already exists.

So, I started playing with a bolter from Warhammer 40k (a 28mm scale strategy game). I decided I needed to do 2 things. The first, was make a base model to drive all others from. This would have the same dimensions as a normal bolter,so I could add or remove additional features without worrying if the bolter would fit the model it was meant to go with (Space Marines):



Bummer. With that in mind, I decided on
With my base model completed, I decided to make a larger, more "assault rifle" version. I increased overall size by around 40% and and removed the front sight aperture in favor of the holographic sight. I also decided to incorporate combi-weapons, the 40k equivalent of under mounted weapons:



The problem? Well, it was too big:



Bummer. So it was back to the drawing board. I decided that I would decrease the size so it was only about 20% larger, and add modular optics, combi-weapons, and magazines. This way there would be much more customization:



It looked better, but there are still size problems. I'll introduce those in my next post.

The second thing I realized I needed to do, was begin making a component library. In Sketchup, a component is an object or objects that are generally considered finished. You can copy components out of the library and right into the workspace. In this way, I could make a base scope mount. Every time I make a new scope, I just copy the mount in and start working, then save the new scope as a different component.

Because I can very rapidly build from a base model or interlocking component, I'm able to add much more variety to my models than would be possible through conventional modelling. At least, in the span of time it takes me.

The downside is that any changes to the base model will require changes to the components. For example, if the top of the bolter were to become wider, the scope mount would have to be changed to match.

Making modular systems requires a lot of pre-planning so you don't end up doing the same work several times, something I've been learning the hard way and will share in a future blog entry (you're going to notice a pattern here).

So, stay tuned. I have some interesting things planned for the future.