- [Instructor] I'm now going to talk about
the extrapolate tool.
I'm going to click on the extrapolate function.
And you can either use the reference document
that you downloaded or, again,
select the F1 key on the keyboard,
bring up the help documentation,
download and open the file provided from Dassault.
Let's get to work.
So the way extrapolate works is,
you can either extrapolate a curve or a surface.
So the first thing it asks for is the boundary,
what edge or what point are you extrapolating from?
So in this case,
I'll select this boundary off of the surface.
As soon as I pick it, you'll notice that
the extrapolated element is extrude number one.
Sometimes you may have to go in there and change it.
It automatically propagates,
and sometimes it may pick the incorrect surface.
But just pay attention, and that way, you don't,
you don't get things criss-crossed or mixed up,
making sure you're getting the correct extrapolated element.
As soon as I pick it, you'll notice that
it creates what's called a linear extrapolation.
So off of that edge, it's creating a tangent extrapolation,
shooting out whatever distance you specify.
You see I can grab this and move this around.
Now I'm going to just take a look at it, down the x axis.
And the reason why I want to look at it
in this direction is, you can see that this length comes off
perfectly tangent and linear.
By default, continuity is tangent.
I can change this to curvature,
and you'll notice that I get a shape change on that surface.
So what end up happening is, across that boundary,
rather than it just being simply linear,
it now uses some of the curvature from the element,
original element, and then it does its extrapolation.
Eventually, it goes flat again, but for the most part,
right across that initial boundary and a little bit after,
it's perfectly smooth.
Other things that I can do with this are,
if I look at propagation mode, right now, it's set to none.
If I change this to point continuity,
you'll notice it picks the entire surface of the boundary
around the entire surface.
This is very handy, because there are times when
you may need to make something just slightly larger.
Sometimes you do offsets
and the edges no longer fall where you need them to fall,
so you can just simply extrapolate those,
make them a little bit bigger,
to bring that edge back down to the spot that you need.
Or maybe you need a trimming element
and the surface isn't quite large enough,
so you would just do an extrapolate,
especially when you go into solids.
So once I specify the continuity type,
I specify my propagation,
I also have down here what's called assemble result.
If I turn that off, what'll happen is,
I'll get a separate surface.
You'll see this is a separate ribbon from the original.
If I double-click on this, turn that back on,
you'll notice that it just automatically joins everything,
in as one singular entity.
Go ahead and delete that.
I can also extrapolate curves.
So I'm going to come in, select my extrapolate curve,
or extrapolate tool,
this, I'm going to pick the vertex or end point.
And once again, this is set to curvature.
You'll notice it follows the actual curvature,
initial curvature of that curve,
shoots it way out in space.
Now, if I come in here and change this to tangent,
you'll notice that it is now just a tangent line.
This is basically sort of just drawing a line
that's tangent at that end point, that's all that is.
If I were to come in and specify that I want
this set element up to, let's say, a specific length,
I can come over here and say, up to element as well.
I also have the capability of, bring this up,
specifying a support.
So even though it's tangent,
as long as that curve sits on that surface,
I can pick that surface,
and you'll see it runs all the way up on that surface now.
I can also, with this length, again I just mentioned it,
we'll say up to element and I'll just pick this edge,
and you'll see it runs all the way up to that edge.
I'm going to select okay, there's my tangent extrapolation.
You'll notice there's a little vertex
that's formed because of the tangency.
If I double-click on that,
and I'll change this from tangent to curvature,
select OK, that vertex disappears,
because it's now a curvature continuity,
it knows to remove that vertex, so it erases that vertex.
In some instances, you need to do that,
to help simplify the secondary or tertiary shapes
that you're going to generate off of that curve.
So the extrapolate tool, very powerful,
you can do tangent, curvature extrapolations,
and you can do entire boundaries around a curve.
One thing that you may want to try as well is,
if you take a look at this,
I'm just going to go into boundary,
I'm going to extract this boundary on that,
and I'm going to create a couple of limits.
You can also extrapolate portions of a surface,
rather than the entire surface,
with those boundaries that you have selected as well.
So you can be very specific
about what you want with an extrapolation,
very powerful tool, and sometimes,
you may get little failures,
depending upon how jagged the edge is.
If you have a lot of faces coming in to a single vertex,
sometimes it has a hard time performing that extrapolation,
but for the most part, you're able to just grab a surface,
again, make it slightly larger
for downstream trims or offsets,
whatever it is that you need
to make a surface or curve slightly larger for.