Divide or split surfaces using Trim or Untrim

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Transcript

00:02

We can project curves onto a subdivision

00:05

and use the curves-on-surface to divide or split the surfaces.

00:10

I'm just going to work on a section of the hood

00:12

and I'll use the Object Lister here to show how the subdivision structure works.

00:18

So you can see we've got these eight faces here.

00:21

So I'll just do a projection in Z,

00:23

pick the subdiv, do a space bar for Go,

00:26

pick the curves, and space bar to Project.

00:30

So we get the curves-on-surface with history on these two faces

00:34

and they're shown here in the Object Lister.

00:37

So when I Trim, I'll pick the subdiv

00:39

and then I could select here to do a Keep

00:43

or move it over here to do a Discard.

00:46

And in the Object Lister, those two faces are now displayed as trimmed.

00:51

But if I was to Untrim that

00:53

and Trim again

00:55

this time, I can say Divide instead.

00:59

And if I shade that up and have a look over here,

01:02

it's created a second subdivision that's been copied from the first.

01:06

And if I give it a shade of color,

01:08

you can see that it's been trimmed to keep that small region

01:11

and the original has been trimmed with the hole.

01:15

But if I try to display the CVs with the duplicated subdiv, they don't appear.

01:21

And that's because of this H for history.

01:23

So the CVs on this one are driven by the CVs on the original.

01:28

So I can only display the original CVs.

01:31

And that means that if I make a modification,

01:34

both surfaces get changed in exactly the same way,

01:37

which is really useful.

01:40

And also they've both got history with the projecting curves.

01:44

So I can scale that a bit or move it

01:47

and they both stay updated.

01:49

But this duplication has implications when you Untrim.

01:53

So if we changed our minds and decided to pick both of those and do an Untrim,

01:59

you notice here that the copy is a full

02:01

duplicate of the original with all eight faces.

02:04

And if I turn off the original,

02:06

you see that the copied one has lost

02:07

the construction history on the curves-on-surface,

02:11

but it's still there on the original.

02:14

So it's good practice if you do Untrim to be aware that you'll have that duplicate

02:19

and to delete it.

02:23

So now I'm going to have a look at a more complicated example on the roof subdivision

02:27

and create some windscreen details using these curves.

02:31

And I will often take a copy when I'm doing lots of trimming

02:35

to keep a simple version of the subdivision.

02:37

If I want to go back to sculpting the basic form.

02:40

So I've got my subdivision note here

02:43

and I'll just do a Z projection again.

02:47

And that gives me the windscreen outlines on the roof.

02:52

So then when I Trim Divide,

02:54

if I want this main roof part to be the master,

02:57

then I pick the subdivision

02:59

and then I'll only select these regions for the Divide

03:03

but leave this main part of the roof unselected.

03:06

So then when I say Divide, you can see over here that that's been left as the master

03:11

and I've got these four extra copies.

03:14

So I can assign some different shade of colors to make that easier to see.

03:19

And that quickly gives me a lot of detail for visualization

03:22

without having to do all that splitting with subdivision modeling,

03:26

which would be a lot of work and add a lot of complexity to the control cage.

03:31

So then if I want to make a modification, then I can display all the CVs on the master

03:36

and history will probably work quite well with small changes.

03:42

But sometimes you get a trimming issue and you'll have to go

03:45

and do an Untrim and a re-Trim to sort it out.

03:49

And that's one of the main reasons why I'll often keep a basic version

03:52

for when I want to go back to sculpting the subdivision.

Video transcript

00:02

We can project curves onto a subdivision

00:05

and use the curves-on-surface to divide or split the surfaces.

00:10

I'm just going to work on a section of the hood

00:12

and I'll use the Object Lister here to show how the subdivision structure works.

00:18

So you can see we've got these eight faces here.

00:21

So I'll just do a projection in Z,

00:23

pick the subdiv, do a space bar for Go,

00:26

pick the curves, and space bar to Project.

00:30

So we get the curves-on-surface with history on these two faces

00:34

and they're shown here in the Object Lister.

00:37

So when I Trim, I'll pick the subdiv

00:39

and then I could select here to do a Keep

00:43

or move it over here to do a Discard.

00:46

And in the Object Lister, those two faces are now displayed as trimmed.

00:51

But if I was to Untrim that

00:53

and Trim again

00:55

this time, I can say Divide instead.

00:59

And if I shade that up and have a look over here,

01:02

it's created a second subdivision that's been copied from the first.

01:06

And if I give it a shade of color,

01:08

you can see that it's been trimmed to keep that small region

01:11

and the original has been trimmed with the hole.

01:15

But if I try to display the CVs with the duplicated subdiv, they don't appear.

01:21

And that's because of this H for history.

01:23

So the CVs on this one are driven by the CVs on the original.

01:28

So I can only display the original CVs.

01:31

And that means that if I make a modification,

01:34

both surfaces get changed in exactly the same way,

01:37

which is really useful.

01:40

And also they've both got history with the projecting curves.

01:44

So I can scale that a bit or move it

01:47

and they both stay updated.

01:49

But this duplication has implications when you Untrim.

01:53

So if we changed our minds and decided to pick both of those and do an Untrim,

01:59

you notice here that the copy is a full

02:01

duplicate of the original with all eight faces.

02:04

And if I turn off the original,

02:06

you see that the copied one has lost

02:07

the construction history on the curves-on-surface,

02:11

but it's still there on the original.

02:14

So it's good practice if you do Untrim to be aware that you'll have that duplicate

02:19

and to delete it.

02:23

So now I'm going to have a look at a more complicated example on the roof subdivision

02:27

and create some windscreen details using these curves.

02:31

And I will often take a copy when I'm doing lots of trimming

02:35

to keep a simple version of the subdivision.

02:37

If I want to go back to sculpting the basic form.

02:40

So I've got my subdivision note here

02:43

and I'll just do a Z projection again.

02:47

And that gives me the windscreen outlines on the roof.

02:52

So then when I Trim Divide,

02:54

if I want this main roof part to be the master,

02:57

then I pick the subdivision

02:59

and then I'll only select these regions for the Divide

03:03

but leave this main part of the roof unselected.

03:06

So then when I say Divide, you can see over here that that's been left as the master

03:11

and I've got these four extra copies.

03:14

So I can assign some different shade of colors to make that easier to see.

03:19

And that quickly gives me a lot of detail for visualization

03:22

without having to do all that splitting with subdivision modeling,

03:26

which would be a lot of work and add a lot of complexity to the control cage.

03:31

So then if I want to make a modification, then I can display all the CVs on the master

03:36

and history will probably work quite well with small changes.

03:42

But sometimes you get a trimming issue and you'll have to go

03:45

and do an Untrim and a re-Trim to sort it out.

03:49

And that's one of the main reasons why I'll often keep a basic version

03:52

for when I want to go back to sculpting the subdivision.

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Divide or split surfaces using Trim or Untrim

Video quiz

When curves are projected onto a subdivision and Trim Divide is used, which of the following is the result?

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When curves are projected onto a subdivision and Trim Divide is used, which of the following is the result?

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Improve your experience – allows us to show you what is relevant to you

Customize your advertising – permits us to offer targeted advertising to you

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Your experience. Your choice.