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to create your own 3d geometry you'll
need to learn 3d modeling
with modeling we mean all methods to
create geometry
we'll go over five main methods amongst
many different approaches
these are poly modeling sculpting cad
modeling
scanning and procedural generation
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the best modeling method depends on how
and where your 3d project will be used
for example you won't use the same
method whether your project is intended
for a digital environment or to be
manufactured or depending on how
realistic or stylized it has to be
the devices it will be viewed on also
might affect your choice
or the fact that it is interactive or
not
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poly modeling means you're in charge of
creating all polygons
edges and vertices for your mesh you
start from some basic shapes
like a plane box or cylinder and then
add edges to it
move parts of it around and extend the
faces
poly modeling is very powerful and
flexible as there's a huge array of
tools and methods to work on meshes
such flexibility also comes with
downsides managing
every single edge and face by yourself
can be a lot of work
and if you're not careful it's easy to
break a mesh if you want to poly model
smooth detailed meshes placing tens of
thousands of faces by hand doesn't make
sense
that's why you can apply a special
process on meshes called subdivision
that will make them smoother and denser
subdivision takes each quad phase of a
mesh
divides it into four new quads while
smoothing out and
averaging the positions of the newly
created vertices
the initial mesh used as the source of
subdivision is called
a base mesh subdividing your base mesh
doesn't destroy it
if you stay within your modeling package
you can always return to the base mesh
to adjust it because subdivision smooths
everything out
indiscriminately modeling for
subdivision means you'll have to manage
hard and soft edges
or you risk your cubes turning into
spheres subdivision doesn't always play
nice with triangles and n-gons the
results are not as good as with quads
there's a bit of an art to creating
clean efficient meshes for subdivision
and many techniques are valid even if
you don't use subdivisions
subdivisions can also lead to complex
meshes that are not easy to work on
and can't be reversed once you export
them to another application
a tight grid-like structure with obvious
loops of quads
make your meshes easier to read and work
within almost every step of the pipeline
if you become good at poly modeling
you'll be able to turn even the most
complicated shapes into efficient grids
of quads
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if you want to add tiny details like
skin pores
dents or irregularities poly modeling
can be limiting
so another form of modeling exists
called sculpting
sculpting doesn't require you to manage
edges and vertices
instead it's like working with digital
clay you use brushes and other tools to
push and pull faces around
and detail can be added by subdividing
meshes many times
sculpting is an excellent approach for
many subject matters
and often it's a second step after
you've made a simple bass mesh with poly
modeling
because you don't work with your
geometry directly sculpting easily leads
to very heavy meshes with millions of
vertices
for some use cases that's fine but for
use in augmented reality or real-time
video games
optimization work is needed we'll come
back to this later
because cad data designs will one day
become real objects
they call for another modeling method
that will author designs in a more
precise and accurate way
with this method you can make use of
techniques like extruding precise
blueprints as geometry
combining solid volumes and designing
smooth sweeping surfaces
cad designs can sometimes be exported as
meshes
or you can use some specific software to
do the mesh conversion for you
bearing in mind that once cad is
converted to mesh there is no going back
sometimes you might want to do the
opposite and bring a physical object
from the real world into the virtual
world of your computer screen
you can also scan 3d objects as you
would scan a sheet of paper
scanning isn't really modeling but it's
the perfect way to capture
three-dimensional things efficiently
there are two main methods for scanning
laser scanning and photogrammetry
laser scanning uses high-end laser
measuring devices
to capture millions of small points in
3d space
giving you very accurate clouds of
points that can then be turned into
meshes
photogrammetry works like our eyes and
brain does
the computer reconstructs a shape in 3d
from a set of photographs at different
angles
both methods result in fairly heavy
meshes that almost always require
extra processing the final frontier when
it comes to creating geometry is where
modeling
physics and programming start to blend
together
you might have noticed that 3d modeling
can be a lot of manual work
that's why solutions have been developed
to generate your geometry
these are complex methods that often
involve defining a rule system
with multiple operations and steps for
example you could use physics
simulations to generate a huge complex
terrain mesh
you could then take that terrain mesh
and place trees rocks and other elements
based on the slope and elevation of the
terrain another
good case for procedural geometry is to
calculate the folds and draping of cloth
over a mannequin
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if you use an existing 3d model that you
just slightly want to customize
there are some simpler techniques to
bend twist and slice your models or to
deform them
and you'll find programs that let you
modify meshes without having to use
actual modeling techniques with a
multitude of tools at your disposal
you might get a bit lost especially cad
modeling and simulations
are not easy areas to get started in if
you're new
poly modeling is considered the staple
skill of 3d with sculpting
being a valuable extra skill to master
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you