GETTING
AND
FIXING
3D
MODELS
13
CHAPTER
Getting Started with 3D Printing 184
INTERIOR_3DPrinting_v21.indd 184INTERIOR_3DPrinting_v21.indd 184 4/14/2021 3:01:05 PM4/14/2021 3:01:05 PM
FIGURE 131 LEFT: A 3D model of a fan shroud provided as a suggested first print from the manufacturer of the 3D printer
FIGURE 132 RIGHT: Aria the Dragon (courtesy of Louise Driggers, used with permission)
In the previous chapters we demonstrated how to make your own 3D models, but if you don’t want to invest
the time learning how to use those programs, you can find a model that’s already been created! In this
chapter we’ll look at the various ways you can find printable models and examine some of the issues you
may find with them.
DOWNLOADING A 3D MODEL
For most people who are getting started with 3D printing, it all begins with downloading an existing 3D
model. In fact, if you purchase a 3D printer as a kit, there is a good chance that there will be recent-
ly-released improvements to your 3D printer you can print. Here is a benefit to using a product that can
effectively manufacture parts for itself! The model shown in Figure 13-1 is a fan shroud, which one printer
manufacturer asks you to print for your 3D printer that would otherwise come fully assembled.
There are quite a few sites on the Internet that host free models, but one of the largest sites is called Thin-
giverse (thingiverse.com). Thingiverse is a great place to find 3D models to download and print out yourself
because many of the models are free for you to download and print for your own personal use. You can even
modify them if you want to, using the software tools we discussed in the previous chapters.
3D MODEL LICENSING AND LEGALITIES
Many of the 3D models you will find for download are provided under what is called a “Creative Commons”
(or CC) license (www.creativecommons.org) and they tell you how you can use that model. You should famil-
iarize yourself with the licensing terms for any model you download to print. The beautiful dragon shown in
Getting Started with 3D Printing 186
185 Chapter 13: Getting and Fixing 3D Models
INTERIOR_3DPrinting_v21.indd 185INTERIOR_3DPrinting_v21.indd 185 4/14/2021 3:01:05 PM4/14/2021 3:01:05 PM
FIGURE 133: Figure 13-3: Creative Commons license with icons
assigned to Aria the Dragon
In the previous chapters we demonstrated how to make your own 3D models, but if you don’t want to invest
the time learning how to use those programs, you can find a model that’s already been created! In this
chapter well look at the various ways you can find printable models and examine some of the issues you
may find with them.
DOWNLOADING A 3D MODEL
For most people who are getting started with 3D printing, it all begins with downloading an existing 3D
model. In fact, if you purchase a 3D printer as a kit, there is a good chance that there will be recent-
ly-released improvements to your 3D printer you can print. Here is a benefit to using a product that can
effectively manufacture parts for itself! The model shown in Figure 13-1 is a fan shroud, which one printer
manufacturer asks you to print for your 3D printer that would otherwise come fully assembled.
There are quite a few sites on the Internet that host free models, but one of the largest sites is called Thin-
giverse (thingiverse.com). Thingiverse is a great place to find 3D models to download and print out yourself
because many of the models are free for you to download and print for your own personal use. You can even
modify them if you want to, using the software tools we discussed in the previous chapters.
3D MODEL LICENSING AND LEGALITIES
Many of the 3D models you will find for download are provided under what is called a “Creative Commons”
(or CC) license (www.creativecommons.org) and they tell you how you can use that model. You should famil-
iarize yourself with the licensing terms for any model you download to print. The beautiful dragon shown in
Figure 13-2 is an example of a user-submitted CC
3D model available for download from Thingiverse.
The Creative Commons license for the dragon model
is marked by the author as “Attribution - Non-Com-
mercial” and reads: This license lets others remix,
tweak, and build upon your work non-commercially,
and although their new works must also acknowledge
you and be non-commercial, they don’t have to license
their derivative works on the same terms.
The Creative Commons license is very adaptable,
and other models may come with different terms. On
many places on the Web, including where you download models from online sites, the Creative Commons
icons look like those shown in Figure 13-3.
The creator of that dragon model (Louise Driggers) licensed that image to us specifically for this book, and
the Creative Commons framework helps attribute proper credit to an asset.
Technically, any 3D model can be converted into a file for 3D printing. But the word “technically” is used pur-
posefully. 3D models created for movies or video games are often protected by copyrights and trademarks.
If you find a 3D model of your favorite character or item from any prominent entertainment company, make
sure its legal to 3D print.
CREATING 3D MODELS WITH YOUR SMARTPHONE OR DIGITAL CAMERA
Not everyone is willing to put in the time it takes to become adept at 3D modeling and rendering software.
Fortunately, there is another way to make 3D models with your smartphone or digital camera. The tech-
nique is called “photogrammetry” and is defined as the science of using images to create measurements.
In this case, you simply take photos of the object you want to model and upload them to a service that will
convert them into a 3D model for you.
In the first edition of this book, there were photogrammetry applications that people could download (even
to a cell phone!) and create 3D models for free. As of 2020, however, most of those free tools have fallen by
the wayside, and not too many free options are left. If you want a free but feature-limited version of more
expensive software, you can look to 3DF Zephyr free (https://www.3dflow.net/3df-zephyr-free/) which is
limited to 50 photos, but does not cost anything to use. One other completely free option is Meshroom from
Alicevision, located at: https://alicevision.org/#meshroom
Another alternative is Autodesk’s software program called ReCap Pro (https://www.autodesk.com/prod-
ucts/recap/overview) but this one has a monthly subscription of about $40 a month. If you are a student, or
Getting Started with 3D Printing 186
INTERIOR_3DPrinting_v21.indd 186INTERIOR_3DPrinting_v21.indd 186 4/14/2021 3:01:05 PM4/14/2021 3:01:05 PM
are part of a non-profit, the software would be free or very low cost. You will want to
take into consideration that Autodesk will also charge you “Cloud Credits” for photo-
grammetry conversion projects (around $9 each), since all of the work is done on the
Autodesk servers.
Although both of the above options are from different software interfaces, the process
by which you create a model is similar….and very easy! Note the program you will use: If
you are using the 3DF Zephyr free version above, you are limited to 50 photos. Autodesk
ReCap Pro allows up to 250 photos per project.
FOLLOW THESE GENERAL BEST STEP PRACTICES:
Make sure you have enough room to take photos of your object from all
sides, from the top, and even, beneath if needed. The space you need around
each object will vary but you will need to be able to comfortably walk
around the object.
You can use any camera you wish (even a cell phone camera) and make sure
to stand far enough back so that the “fisheye” effect that happens when you
are very close to an object is minimized. Each camera lens is different so
make sure to do some testing.
Take pictures of the object from all different angles and elevations, overlap-
ping each picture by about 30-50 degrees depending on how many images
you can upload.
Make sure to raise and lower the camera as you take the pictures to get
underneath any overhangs, the top of your object, and other surfaces you
can see.
Load the photos either to the cloud service or into the local photogramme-
try application and wait for your model to be exported.
The resulting file can be edited in Meshmixer, or on any STL modification
program.
If you see that you missed some areas, photograph them again and add
them to your past group of photos, run the photogrammetry again and test if
the resulting file looks better.
There are some special considerations for creating photogrammetry of objects
outside. In this environment the light from the sun and clouds changes quickly so you
will have to work fast. Here are some other tips:
Getting Started with 3D Printing 188
187 Chapter 13: Getting and Fixing 3D Models
INTERIOR_3DPrinting_v21.indd 187INTERIOR_3DPrinting_v21.indd 187 4/14/2021 3:01:06 PM4/14/2021 3:01:06 PM
Try to avoid sunny and partially cloudy days. To get the best results you will
be balancing the light and diffusing the shadows.
Use a tripod even though handheld cameras are faster. The shaper your
images, the higher quality your scan and textures will be.
Fill the frame with your object. There is a fixed number of pixels in each
image so use them wisely by filling the frame with your object! You will get
higher resolution scans that way.
Use a small fixed aperture size. You want your entire object to be as sharp
as possible.
Use Aperture Priority mode often seen as the Av symbol on your camera.
This will automatically adjust the shutter speed to get an optimal exposure.
Use a Shutter Release Cable to get shaper images. This tip is optional but
we found it increases our ability to not move the camera when taking a
photograph.
Take notes on what you scanned and what order will help you organize the
images.
Take real world measurements of what you are scanning so that you can
scale your scans to the correct relative size. This is a good tip for indoor or
outdoor scanning.
This last tip is easy: Move fast and stay focused! When taking photos
outside, you are at the mercy of the changing weather and light. Capturing
the images in the smallest amount of time possible gives you the best
chance of capturing images you can use.
After you have had some fun trying photogrammetry with the above tips you can
research a promising project called OpenScan (https://en.openscan.eu/). This
project aims to provide a set of 3D printable components you would be able to match
with low cost stepper motors. This will allow you to automate the process of getting
images and to tinker with the hardware setup.
PHOTOGRAMMETRY OF ORGANIC SHAPES
Photogrammetry has another advantage in that it makes capturing organic shapes
easier. 3D modeling programs can create complex 3D models from scratch, and by
using artistic ability, it can help you create organic models. The problem is that it will
take a lot of time to create the curved organic surfaces, whereas with photogram-
metry, they can be created with a set of well placed images. Unless you are a trained
Getting Started with 3D Printing 188
INTERIOR_3DPrinting_v21.indd 188INTERIOR_3DPrinting_v21.indd 188 4/14/2021 3:01:06 PM4/14/2021 3:01:06 PM
..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset