- [Instructor] Box modeling is a term that's sometimes used
to refer to subdivision surface modeling.
That's because with sub divs, we almost always start
from a box primitive, like this one.
As we saw in the previous movie,
a box is composed of all quadrilateral polygons.
Which is the optimal structure for sub divs.
Before modeling with sub divs,
we should establish an appropriate level of detail
for the control cage.
Remember that the box, or the original base object,
is merely a control cage,
it's a means to an end for shaping the object with sub divs.
In preparation for that, we should try to determine
roughly how many points we need on that control cage.
Too few vertices or control points,
would make it impossible to resolve the curvature we need.
We literally wouldn't have enough control.
Too many vertices on the control cage
would force us to micromanage many points,
and that would defeat the purpose of sub divs.
Also, too many vertices can result in a lumpy, messy output,
instead of a smooth, flowing curvature.
We want to find the sweet spot
for the control cage level of detail.
We can always add and remove detail
from the control cage during the modeling process,
but the work will go more quickly,
and dare I say it, more smoothly, if we plan it out well.
Generally we want to model the overall shape first,
and then proceed to adding small details.
In other words, work from big to small,
or from the general to the specific.
In this case it makes sense to start with a control cage
with vertices approximately from five centimeters apart.
With that box selected, I'll go to the modify panel,
and increase the number of segments.
We'll give the length segments a value of eight,
and we'll also set the number of width segments
to a value of eight.
It's actually important in this case to use an even number
for the width segments,
because we're going to be employing the symmetry modifier.
That lets us model just half of the seat cushion,
and automatically reflect the mesh to the other side.
For that to work best,
we want an even number to the width segments,
or the number of segments along the X axis.
That will result in an edge loop, or a seam,
right at the center of the object.
Precisely on the symmetry modifier's reflection plane.
Okay, I'll also increase the number of height segments,
so let's bring that up to a value of three.
Now I've got control vertices
spaced approximately five centimeters apart,
everywhere on the model.
With the initial level of detail set up,
we can go ahead and convert this to editable poly.
In the viewport, right click and choose convert to,
convert to editable poly.
Since we're going to be using symmetry,
it's a best practice to delete half of the model,
on the side that's going to be generated
by the symmetry's reflection.
This isn't strictly necessary, but I do recommend it,
because otherwise you may have issues
with the symmetry and not even know it.
To prevent any issues,
I'm going to delete half of the model.
Go into polygon sub object mode, and in the front viewport,
click and drag to make a selection around all the polygons
on the left side, or in the negative X axis.
And you might want to orbit around in your perspective view
with alt and middle mouse, just to double check,
and make sure that you've selected
what you think you've selected.
And then delete those,
just by pressing the delete key on the keyboard.
Now we have half of a box, with an open border.
I'll exit out of polygon sub object mode,
and I can go into the move tool,
just to illustrate that the pivot point,
or the center of the object,
is precisely on that seam, or on that open border.
And again, that is helpful for the symmetry modifier,
because the pivot point is the default position
for the symmetry reflection plane.
We set this up so that it's going to reflect those polygons
to the other side, along the open border, or along the seam.
That's how to set up a box primitive
in preparation for symmetrical modeling with sub divs.