- [Instructor] If you look closely
at a spine curve,
you may notice some segmentation.
You may see that it's not actually a smooth curve
and it's got a bunch of straight lines.
Now, this is not really the true state of the spline.
The spline is mathematically perfect
but in order to display it on the screen,
it needs to be chopped into straight line segments
and the segmentation
is kind of coarse, it's kind of blocky
and that's because 3ds Max is over 25 years old
and 25 years ago, computers were a lot slower
and they couldn't handle as fine a segmentation
as they can now.
But we can control this and optimize this.
And it's important not just for the aesthetics
of the display, it's important especially
if you're going to use this spline curve
as a basis for some three-dimensional object.
If you do that, then you might find
that the interpolation settings
in the spline actually affect the end result
of the object.
Let's take a look.
I'll select the spline curve.
Go over to the modify panel.
And we see that there's a rollout here
labeled interpolation.
And that's going to determine the segmentation.
The more steps we have,
the more subsegments we will have
between points.
And it'll be easier
to see if I enable vertex subobject mode.
We can see that I've got three points here.
And between this point and its neighbor,
there are currently six segments.
There are six divisions.
That's because the default number of steps is six.
As I increase this, just click and drag,
release the mouse,
bring that up to a really high value,
like almost 100
and we get a really smooth spline curve.
Maybe I'll bring this down to a value
of something like 20.
And that's probably good enough.
Or if we bring the steps around to a really low value,
like let's say one,
then we get a really blocky segmentation or decimation.
And if we bring the number of steps down to zero,
it's as if we had only corner points everywhere.
We're getting no interpolation.
Interpolation is the filling in of data
between known values.
So for this Bezier spline,
the positions of each one of those control vertices
and each one of the tangent handles,
those are known values.
We can take those known values
and then interpolate or sort of fill in the blanks
between those known values
in order to get, in this case, a smooth Bezier spline curve.
Okay, I'll bring this back up to its default of six.
We have some options here.
We can, for example, enable adaptive interpolation.
When that's on, 3ds Max is going
to create as many interpolation steps
as it thinks are necessary
to create a nice smooth spline curve.
We don't have any control over that.
It's just a process that happens automatically.
And we can see this a little bit more clearly actually
if we make this spline renderable.
It's kind of a bonus in this particular lesson.
Let's go into the rendering rollout.
And we can see, if we go up to the top,
we have some switches here.
Enable in viewport.
Let's turn that on
and then additionally increase the thickness.
Just drag on that spinner and increase that.
Make that really a lot larger.
This is now actually a 3D object,
it's not just a spline.
It's now actually a polygon mesh
because we've turned on enable in viewport.
If we turned on enable in renderer,
then this object would actually render
as a tube in our renderer.
Okay, so this is actually showing us
the segmentation really clearly.
If we go back to our interpolation rollout
and we turn adaptive back off again,
we can see that okay,
we're getting six segments there
and if we turn adaptive on,
we're seeing the segmentation.
But that adaptive segmentation is going to change,
depending upon the shape of the curve.
If I grab the selected move tool
and move one of these points around,
we can see that the segmentation
is going to change, especially if I, for example,
change the tangent handles, move those around
and the number of segments is going to change
as I change the shape.
Okay, that might be desirable but it might not.
I don't tend to use adaptive mode very much
because I don't have any control over it.
So I'll turn that off.
And I can set the number of steps manually
to something like let's say 18.
Then finally, we have the ability
to optimize straight line segments,
and that is on by default.
So if I turn optimize off,
then I'll get 18 segments over here
in this straight line area.
These are corner points here.
So the segment between two corner points
is always going to be a straight line.
And you may or may not want optimize on or off
depending upon what you're doing.
If you're creating a 3D model
that needs to be deformed later, for example,
then you'll want to have that segmentation there
so you'll have something to deform.
But if this is going to be a static object,
then maybe we don't want all that segmentation.
So if we turn optimize back on again,
we'll get a more efficient object.
It'll have less polygon density here
and that may or may not be what we want.
Alrighty, so that is how to work with interpolation
in order to optimize the exact level of detail
for a spline curve.
And maybe I'll go back in there again
and turn my rendering off,
turn enable in viewport
and enable in renderer back off again.
That's how to work with spline curve interpolation.