Several of my YouTube subscribers email me regarding the Sweet 2 surface, so
we're gonna spend some time to talk about it today. Hi, welcome back to
PJ Chen Design Channel. This channel is about sharing Rhino 3D knowledge to
students and 3D model professionals learning various Rhino techniques.
Are you ready let's get started.
when we're working with Sweep2 rails surface,
we will have this window come up and then this window we can talk about the
difference on top three. The first one I already have pre-made these rails here.
Let's take a look on the perspective view, alright so the red ones will be
my rails and the green ones will be the cross sections, so let's go to the surface
Sweep 2 rails and you got rail one, rail two, and then it is the open curve cross
section we click on all of them then we will have the surface like this. I'm
going to move that into this section here for "not changing the cross section"
The second thing we want to try is the second option by changing the cross
section, so here is the Sweep 2 rails we go rail one, rail two, in the same cross
section. then we have this dialogue coming up right here. You can change as
many as you want. You can pretty quick to see this preview here. and the cross
section become all of the points, so we set it for 12 points, and I'm going to
click OK and this section.... actually I already have one made here, so you
already know the surface is slightly different. In a render view is actually
not much different, but you're going to see your difference when you
turn on a control points. The third one is actually going to change the.... we are
going to change the height you can refit the cross section within certain
distance. We're not gonna do that because that's pretty much the same like
a second one, so we are talking about maintain the high here. Let's go to the
Sweep 2 surface okay we have rail one, rail two, cross sections
again come with the dialogue window we want to make sure we maintain the high
and what it does is the height will be maintained and will go smooth from the
first cross section to the second cross section. I already make another one there
if you go by the comparison from the second one which is the green and also
the third one is the maintain the high. You can see the third one coming down
smoother. The first one the highs actually go by the distance in between
first rail and the second rail. Alright so the very last
one we want to try, We have to go from the top view in order to see it. okay so
We're gonna go into the surface again Sweep 2 rail, and again first
rail, second rail, cross section, and cross section. Alright now nothing
is different here we still maintain a high okay we do not want to change the
cross section. We will try to keep the wireframe as square as possible, so you
have the option right here it's called "add slash". alright so what we wanted to
is we want to go as 90 degree as possible. okay so I gonna go from rail
one and then move it to the rail two, and that's trying to do as 90 degree as
possible .okay so keep all of them into more of the square looking. I think this is
good here. Alright and then if we like that we can
click OK. if not, you can add more slash in there. right so what it does is you
give you more uniform looking. now let's take a look
how are those surfaces are going to affect the look on the mesh. so I'm going to
make them into the mesh, and let's try fewer polygons easier to see in that way
okay so I'm gonna select all the mesh that we just create
and move them into this box right here. Now if you take a look on this, you can
kind of notice the first one and the second one, they are very zigzag you can
see the you know the edges are really zigzag and also that's actually because it's a
low polygon. You're probably gonna see that anyway ,but what is going to be
interesting is by comparison you're going to see those it's more like kind
of in some point a kind of folding into themselves. This one is not as bad. As you
can see from the original surface is small squarish looking, and this one is
come out really good as you can see the area is really smooth. so let's turning
to the render view. let's do some comparison. What I wanted to look at it
is the angle right here. You see even in this the mesh this kind of very smooth
compared to this one, you can see how rough the surface is, and sometimes this
is a simple form, sometimes when you have really complicate like... if the curve is
like a really small radius, it kind of curving into it.... like a lot of nice
scrolling work, then you may have a problem. It's like too much turning once
you're turning to the mesh, they kind of break it. So in some scenario you have no
naked edges on this surface, a NURBS surface, but you do have naked edges on
the mesh. That is why is that happened. Okay, so we try to create use
this method to understand what it's the better surface. Okay now the other
scenario is instead of the open curve as a cross-section, we do have closed curve
as a cross-section, and what I mean is if we do surface Sweep 2 rails, and this is
rail one, this is rail 2, and you go from here to here to here okay
and this is where the direction should go. Imaging that, I'm gonna call the rail
one the interior, rail 2 is exterior. All the points should be lineup
exactly the same point. okay and then all the arrows should go into the same
direction. In this case, they all face down so let's take a look on that then
we will have a very nice surface right there. Okay I already did that
one so that was the same like that surface, so we have that one there, what
happened if the arrow is not aligned, so rail one, rail two, you got 1st, 2nd, 3rd and
I'm gonna just gonna flip it. You go to click on the arrow on the second one, I'm
gonna flip it up, so that means when this cross section turning into here it's
going to be turn to the opposite direction, and then coming back with
another opposite direction and let's see what happened here
okay so you see the form was like this is because well the arrow was lined up
but it was in the opposite direction that's why it calls this issue so he
folded twice. this is the first one right here. this is the second one right
here, as you can see they are kind of cross okay so we try to align with all
the arrow. What happened if the dots are not align. Let's go to Sweep 2 rail again
rail one, rail two, cross sections, here, here, and here okay
instead of a line right there. I'm going to move arrow to the other direction, so
you can see that they are not aligned however the direction is the same so
let's see what happened is I'm going to click OK
okay and what happened is this was circle and because it's going to turning
here and become a oval, you can kind of see the
form it's kind of twists itself, and then coming back twist again back to the
circle, alright. So if your arrow position is not align, the form itself it will
twist. It's almost like turning 90 degree in my case, so even though they are
following your rail, they won't be exactly match your rail. Okay so that's
why make sure that- all the arrow position are align, and the direction is
aligned to otherwise you will have some sort of arrow like this. This is not
really a error, but it may not be exactly what you are looking for. I hope today's
tutorial is helping you understand more about how to use the Sweep 2 Surface
option. Please like and comment and share my video, because that's helping my
ranking on YouTube, and that's the only way that I can keep making free tutorials
for you. Thank you for watching I will see you next Monday!