概述:

Rendered characters look awesome but you can't put them on your desk or monitor. I guess it's no surprise then, that they form a substantial part of our printed models.

You may find that your existing models aren't always directly suitable for 3D printing though, so we've prepared this tutorial especially for you.

It's is not a tutorial about character modeling – there are already plenty of those around on the web. Instead, we'll focus on tips and tricks for getting the best possible 3D printed result.

1. the basics: creating a watertight model:

Of course, the first and foremost requirement for being able to 3D print your model is that it needs to be watertight.

I think it deserves some extra attention here because as a character modeler, you may be used to model only the visible parts. The backfaces of props, clothes, eyes – all these are usually left out because they won't be visible when rendered anyway.

For Shapeways though, every surface in your model needs to be closed. Even if two objects overlap or intersect, they both have to be closed. You'll make our printers cry if you don't.

In addition, the face normals of the object all need to point in the correct direction: outward of your object. We're using the direction of the face normals to determine what's the 'inside' and 'outside' of your object. Inside and outside mean 'printed material' and 'air' in our case.

You'll need to pay extra attention to this if you create hollow parts. Again, always make sure the normals point towards the air, as in the following diagram:

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For more information on this topic, please see our tutorial "修复非流形数据模型"

2. using a rig to pose your model:

You can use a rig to pose your model. Just don't use any extreme distortions - these can cause problems with your face normals when 'inside' faces are pushed to the outside.

As far as I can tell, manifold/watertight objects will stay manifold even when they're changed by a rig. If you start out with a printable model and then pose it with a rig it should remain printable.

Shapeways can also handle self-intersecting models to a reasonable degree, although coincident faces can sometimes become a problem. If our upload check rejects your model, re-pose it slightly and try again.

Finally, Shapeways can only handle model information – not rigs. You'll have to 'bake' the pose into the model before exporting it.

3. make the arms and legs strong enough:

I'm probably stating the obvious here but some parts of your model may have to endure some rather large forces. For example, creating a very fat (and heavy!) character on two very thin legs is a bad idea as they might just snap off under the weight.

4. but will it actually stand?

In your 3d application your model will always stand nicely on it's feet, but if you don't take care your REAL model might just keel over – you'll need to examine the location of your object's center of mass in relation to the size and location of the contact points with the floor.

If you're lucky, your 3D app may have some kind of physics simulation or center of mass calculator that you can use. If not, here's a trick I like to use:

Draw a curve around the contact points of your object with the floor. Next, take a look from the top of your model and see if the bulk of its mass fits inside this curve. If it does, it'll be pretty stable. If it doesn't then you may want to take some additional steps (see below).

Also take the shape of the contact area into account: it should be circular-ish.

An Example:

Here's an example. Cornelius here has a big head and a fat tummy, but only two very tiny feet. The red area is the curve that I drew around his feet. In the image on the right you'll see that the contact area is very small compared to the entire character.

Another view:

As a result, the contact area is now MUCH larger and the resulting printed model will be rather stable.

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The height of the object is of course also a factor: higher objects will be more unstable. Take another look at the position of your center of mass. Next, measure the average size of the contact area. A good rule of thumb is that these two sizes should be roughly the same.In the case of Cornelius, I estimate that the the center of mass is about at the height of his arms. This relates nicely to the size of the contact area so I'm still confident that this character is stable.

Examples of this method:

'Petunia' here can stand, but as her mass is too far to the front, she turned out quite unstable.

'Toon Hen'has nice big feet that are well placed with respect to the center of mass:

5.adding a base for stability

Another approach is to add a base to your model. Again, make sure that the center of mass is well inside the base area (ideally at the center) to get the most stable solution.

A drawback of this solution is that a base will require additional material so it'll also raise the price of your object. Even a small base with a diameter of 5cm and a height of 2mm uses about 4cm3 of printing material.

Examples of this method:

'What the Duck'

'Ode to the Boogieman' is a nice example of a base that's integrated into the design of the model (see how the top-heavy head sticks WAY out of the model?)

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While you're at it you can of course use the base in your design – add some floor details or the design's title to it!

6.using props for stability

If your model allows it, you can also use props to give it stability. Maybe you can make your warrior lean on his sword or let a dinosaur's tail touch the ground.

Examples of this method:

'Dwarf Priest'

'Hungry!'

8. saving costs:

Once your model uploads fine and the website accepts your model, you'll get a price quote. Here are some tips for making it fit in your budget:

1. Make your model hollow. You don't pay for what you don't print, so by removing the interior of your object you can slash the printing price. Do take care of the proper orientation of the face normals though, like I mentioned earlier.A common method for making an object hollow is by extruding it inwards. This can cause sharp corners to push through the wall as indicated below. Smoothing out the inner wall usually solves this problem. The animation below illustrates this (thanks, DaddyMack!)

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Make it smaller! You'd be surprised at how well this works: the printing price is directly related to the printed volume, and volumes are the third power of the object's sizes. Make the object half the size and the volume will become an eighth! To help you calculate the right size for your budget, we've created our Size Calculator. Just plug in the current price and your target price and we'll tell you just how much smaller (or larger ;-) you need to make your object.

Examples of this method:

Tutorial '如何创建有孔洞的物体模型'

Maya users will find some Maya-specific tips on hollowing in the tutorial '从Maya中导出COLLADA文件