- [Narrator] Now that we've created some
curves and surfaces, we need to analyze them.
So under the analysis tab we have show poles and show knots.
And the way these work is you select
the curves or surfaces, and I'll use some curves first,
then I'll get into some surfaces,
and I'll just pick these as a chain, and turn on show poles.
This will show me the actual
control polygon of those curves.
Let me pick these again, and now I'll show knots.
Knots are internal breaks.
You can see that here, within the curve.
So it's almost like if I were to join these two curves,
that knot point would be where the boundary
of those two curves come together.
So that's basically an internal knot point.
I'm overly simplifying it to give you an
idea of what that is, but that's kind of what it is.
Now if I double-click on this curve,
you can see this is a through points.
And if I increase the points on that,
and increase complexity, you'll see I have additional
knot points that show up, as well as control points.
I'm just gonna cancel that.
So this bridge curve, for instance.
If I double-click on that.
Now if I modify this bridge curve I can see
mathematically what's going on to that bridge curve.
You can see I have here control points,
because I'm using a simpler continuity.
G1 is just simply tangent.
So now that shows me those control points
and how they look and where they're at.
If I manipulate this a little bit you can
see those control points also change and move because
those are the actual shape of the curve mathematically.
Select OK.
Now, another way to use the show poles and the show knots,
let me go ahead and hide these.
I have a through curves set up,
I'm gonna show that, and do a fit.
Pick my surface and I'm gonna show poles,
and these are the control points of that surface.
You can see I have a whole heck of a lot of 'em.
And I'm gonna also show knots.
Again these are internal patches and those are
not necessarily seen, but those increase
the complexity of the surface.
For every additional knot we have, there's more complexity.
So this is a fairly complex surface.
Now if I go into that through curves,
and I double-click on it, you can see here
I have an alignment set to arc length.
If I change my alignment type, go to parameter,
you can see that there's a difference
in the shape on that surface, so this is a great way.
You create the surface.
Once it's there, you go, you apply the knots,
you apply the poles, and now you can visually see
what happens mathematically as you make some of these
changes to your mesh surfaces,
your sweeps, whatever it may be.
Also, if I scroll down a little bit,
you'll notice construction is set to normal.
If I change this and say simple,
I get a much simpler surface.
So there's a lot less math on that surface.
So this shape obviously has to change.
How much it changes depends on how radical a shape you have.
Now, if I start changing some of the
continuities as well, you can see once again,
shape changes fewer of those knots and control points.
So, using the show poles and show knots,
really very helpful to verify what
you're looking at is good, clean math;
is good, clean surfaces; good, clean curves.
To turn them off, you can just simply pick that surface.
Once again, you'll notice it's basically
like on/off switches, I can now just
select them to turn them off.
And now the surface and curves operate the same way,
no longer have those on as a display.