WEBVTT

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Hello and welcome to scripting for artist.

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My name is civilian and in this episode we will be looking at linking of assets

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because there is a lot more code in this episode than in previous ones.

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And the code is getting complexity as well.

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I've put the final add on in a link in the video description so you

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can download that and use that as a reference while you're watching this video.

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Now we'll go to blend a cloud to take a look at the settlers project.

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It's a public project so you don't need to blend a cloud subscription to access this

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and it will serve as a nice example for this episode of scripting for artists.

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I've also put the link to the project in the video description

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here is the animation of blender cloud of the settlers

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project as is typical for such animation projects it's seen

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has set and each set consists of assets in this

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case like rocks and plants here on the left.

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You can see in the set development different blend files

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for the rock assets and for the correct I assets.

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They're all linked into the environment file here.

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You can download the debtor trial.

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Just click on the download button here and this will give you the following files

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here. I've unpacked the files into Atlanta desert. It has an

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little notes and a sets directory. The ends directory has the environment assets.

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So the desert plants and rocks.

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Notes has some shade as we won't be looking to

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those and in sexual find Atlanta desert dot blend.

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I have already created the Jason file that we're going

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to use of course in the preparation for this video

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and we have a new setup plant which

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we're going to build up automatically from scratch.

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Now before we start Ultimate NG things,

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it's always good to take a look at blender itself and manually

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go through the steps that you want your script to perform.

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So typically you would go to a while and then link,

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you would go to the environment assets say rocks

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and there we have collections that we want to link in.

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The naming is as follows,

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you have E N dash which stands for environment

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asset and then there is a name and number.

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So we want to have all the N rocks,

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we want to have all the smooth in rocks is like the entire thing.

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Um,

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we don't want that 11 thing you can already

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see is that all the collections have a certain prefix

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this we can use in our script so that it will automatically pick up the right ones.

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So, and ash rock underscore s underscore. That will work for the first set

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and Ian dash rock underscore smooth underscore will work for the second set.

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Now let's just link in one of those.

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You click a link and automatically blender instances this into the scene.

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If you want to link this into our seen ourselves in our script,

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we have to investigate further into what this actually is.

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So what we have here is an object and is actually an empty object

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with instance ng set to collection

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incensing a collection from rock stop blend

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furthermore,

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the empty is of course part of the same collection

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and that is why it appears in our scene.

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So this is what we have to do.

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We have to Lincoln the collection from the

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rock stop blend into the current blend file.

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Then we have to create an empty and that

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empty will instance that collection into our scene.

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Now contrary to what we did before, we're not going to use as a link operator.

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It's very hard to use from python and there is a much

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better way to do this if you go to help python,

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api reference

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and then so for bP data libraries you find it's a library.

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Data blocks of type B pi data libraries, click on that

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and here you will get to the load function.

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So this is what we're going to use be pint of data to libraries that load

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this takes a file path,

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it takes a link parameter that can be set to true if

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you want to link which is what we want to do.

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Otherwise it would depend to the current file

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relatives should be true if the file path is

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to be interpreted as relative to the current blend file

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here are some examples of how to use this function.

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The function actually acts as a context manager,

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which means that you use it with the with statement.

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A with statement has an indented body

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so you have to with then you have an expression here then

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you have Colin again like we know from the while etcetera.

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And then again you have a bit of code that is

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indented that is called the body of the with statement.

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Now the with statement does something before it enters

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the body and then it does something else when it

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exits the body you can use this for all

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kinds of things like opening file and reading the content

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and then making sure that when that with statement

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is over the finals automatically close again cleaning up.

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I should go.

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In this case it loads the blend file and it

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exposes the contents of the blend file in data from

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and then you can assign to data to whatever data

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blocks you want to link from that blend file,

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the data from and data to.

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They look pretty similar to the b part of data that you already know.

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So it has a dot teens dot object of collections etcetera.

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The only difference is that they're not really objects or scenes or collections.

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They're just a list of names.

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So we can act based on the name of the scene. The name of the collection.

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The name of the object

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and whatever names we give to data to

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will be finally imported when the with statement is

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over here in this example it appends the

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scene called scene to the current blend file.

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It depends because the default for link is false. So that's the default behavior.

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There is no link parameter given. So it will append

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down here. You'll see an example

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with links. True. So that will link instead of appending

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the data to dot scenes. The measures that object etcetera are lists

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like we've seen before. So we can also append things to them.

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Similar with data from data from the collections is also a

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list of collection names so we can loop over those.

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This means that we can loop over the collections, look at their name,

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see if the prefixed with the prefix that we wanted to have and if.

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So we append them to the data to dot collections list.

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Now let's go back to blender and write some code to

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explore this a little bit and see how it behaves.

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So Rebecca blender and this will all look

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pretty familiar by now we're importing beep.

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I

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we set a file path and because I've saved this file inside the sets directory we

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have to go one directory up then two ends and then we have rock stop blend.

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The rest is pretty similar to the example that we've seen already.

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So we have with BP data libraries load

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then the final path and link equals true because

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we want to link and then we have as data from accommodated to as we expected.

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Now all we do here is print data from the collections just to

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get a peek on what is exactly in there for our particular file,

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click play and then we go to the terminal where we started blender.

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If you're on windows you can go to window and then total system console

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in order to see this

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here we see that list of collection names.

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Just like we saw in blender itself when we manually went through all the steps.

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Now, even though we didn't actually link anything from that blend file yet,

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it did have some effect.

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If you look at the outline er

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you can see that it did load the rock stop blend file that we wanted.

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So it's already doing something

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now we have our list of names,

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let's do some filtering on the names that we find

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interesting and actually link those into the current blend file

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for this. Let's first determine our prefix. So remember we had two sets of rocks.

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Let's just focus on one now and then we'll do the other later.

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And that started with the n dash rocks and score as underscore

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we can remove this print

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and just say for collection name in data from the collections

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if it doesn't start with our prefix, we're not interested.

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So we skip them by using the continue keyword.

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This will just tell the for loop to go to the next element and skip the rest of the body.

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In other cases though we have the prefix and that means we

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have to tell blender that we actually want to link this collection.

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This means we have to do something dot data to dot collections

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and says that list we can append to it.

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Let's give this a try.

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This will work fine

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and now we can open this file in the outline er

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and we can see that these collections have been added to it.

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These are exactly the collections that we wanted and all

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the collections that we didn't want are not here.

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So our code is doing the right thing.

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Now all that's left is to create an empty that instances

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these collections and then link those empties into a same collection.

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There's something special about this data to within the body of her.

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With data to dot collections is a list of names but once the with

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body is done and deploy data libraries that load has actually loaded what we needed

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data to dot collections is no longer a list of collection names.

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It's actually a list of the collections that were linked in.

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So what we can do is looped over them.

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Now here cole is first the first collection then the second collection etcetera.

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Now let's create an empty

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it should be named after their collection

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and it shouldn't have any data.

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This way blender understands that this object should be an

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empty and not a camera or measure anything else.

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Now we have to set some properties and let's take a look at what those are.

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So just to test I add an empty empty,

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I have to set Lisbon which is object of instance type.

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And of course we have to set the collection to

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one of the collections and there you have it.

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This is all we need to do.

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So however over here and you say it's instance collection. So we have to set

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instance underscored type

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and instance underscore collection.

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I'm guessing that instance underscore type will have to have the value collection

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but we can always look that up. Of course.

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Yeah.

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And there you have it. The instance type should be set to collection in capitals.

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So let's just copy this.

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Yeah.

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And then we have that

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and instance collection is of course the collection

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that we want to instance which is coal.

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This will create the empty but it's not yet part of our sane.

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Now I think it's nice to create a special collection to have

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all these empties rather than having them at the top level.

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So before we start doing this we want to make sure that that collection exists.

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Okay

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seen as beep.

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I context seen later when we change this into an operator that does all the work.

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Of course we we use context that scene and not be pint of context. That scene.

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But for now this will suffice

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let's say that the collection that we want

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to link everything to should be called environment.

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Now

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I want to create this collection but only if it doesn't exist yet.

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The easiest way to do this is just to act as if it already exists

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and then see what error occurs when it doesn't exist yet.

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And then simply handled that case.

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So let's do the simple thing first.

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Let's say it already exists.

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Then we can access this collection through the scene

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like this.

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And it would just give us a collection

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if it doesn't exist yet.

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Okay

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mm.

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This will raise a key error.

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Now we have the information that we need.

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Let's go back to the code as we've done before. We want to use try and accept

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so we tell python try this for us.

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And if this fails we'll have to create a new collection.

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Okay.

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And then once that collection is created we have to add it to the same collection.

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Okay.

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So now this code will just use the existing

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collection if it's there and create a new one.

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If it isn't now that we have the collection we want to link to.

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We can do they're just that.

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Yeah.

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Yeah.

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And this will linker empty.

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You can see that running now to considerably longer.

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And here we have all our assad's linked into the file.

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They're all empties

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they're all inside the environment collection.

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And we don't have anything we don't want to have

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now as a final touch.

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Let's line up all the empties in one line along the X axis so

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that they're nicely spread out and not all lumped in one spot for that.

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We have to keep track of the X. Location of the previous empty.

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So let's just start at zero

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and let's give every empty to blender units

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now that they're linked to a scene, we can set their location.

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Okay.

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And then we can increment location X by step X.

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So that the next empty will use the next location.

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That's delete all the MTs. Run the script again

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and there they are all neatly lined up.

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Our script is working but it's very limited.

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If we want to load assets with a different prefix we

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have to go and change this prefix in the source code.

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Run the script again,

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if we want to load from a different blend file we have to do that again.

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If you want to link the empties into a different scene collection

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again we have to edit the script and run it again.

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It will be much nicer if we had a file that contains all this information it

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contains which blend files to use which prefixes

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to use which collections to link into.

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We can then put our code into an add on that doesn't need to change

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and other projects specifics go into a separate file.

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Before we do that though, let's copy our code,

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put it into a separate python pile

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and shuffle some code around into separate functions

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so that we can work with some higher level building blocks in

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stata of looking at one big blob of code all the time.

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So let's copy what we have now

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and go to the add on. I already prepared we've seen this a bunch of times.

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It's just a python file with a bill info

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we improve beep. I

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I've already added the operator with an empty

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execute functions or will feel that out.

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It is added to the import menu so that we

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can just to file import and then load stuff from Jason

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and we have the blender classes where we have the operator

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class and the registered and unregistered functions that we've seen before.

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So above all of that let's paste the code with that

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we just copied and let's turn this into some functions.

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So there's a few things going on here at the same time.

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This first bit is linking data into the current blend file.

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Then we have some code that creates a collection for us if it doesn't exist yet.

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So actually that's quite a different thing so

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that can be moved into a different function.

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Then we look over all the collections that we linked into the blend file.

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So this actually belongs to the first bit of code.

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So let's take this part out and start writing a separate function for it.

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Mhm.

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Let's call it ensure collection because it ensures that the collection exists.

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It needs access to the scene.

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It needs to know the collection name of course.

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And then we declare that it will return the collection.

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Let's move our code in here

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and change that collection name.

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Now all we have to do is return the link to collection and then this function is done.

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Now we have the other bit of code to look into.

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Yeah

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let's call this function linked to a scene.

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It will take the file path as a parameter instead of having it hard coded here.

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Similarly, it will take a prefix as a parameter instead of hard coding in here.

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Then we have the link to which is a collection and then the location.

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Why later on we will be linking multiple sets of assets from multiple

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blend files and then having them in different rows is kind of nice.

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So that is why I added a location, Y, parameter here as well.

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Now the rest of the coat needs to be

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invented because it needs to be part of the function

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and of course now we also have to set the wild location

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so we can do that like this.

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Now that we have are two functions, we can just call these from our operator

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still with the same hard coded values that we used before

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so that at least we can see that they're working.

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So first of all we have to create the link to collection.

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Yeah.

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And then we can call linked to a scene with the

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same file path and the same prefix as we used before.

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Then the collection. Then the collection we want to link to.

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And let's just use zero as the wild location for now.

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Now of course you have to enable your I don't you know how that's done

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now you have to install and enable your adam.

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If you want to have a refresher on how that is done.

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Look for the scripting for artist chapter called from script to add on there.

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It's all explained.

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Now you got to file import link assets from Jason

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and you can see that everything works as expected.

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Now it's time to look at the Jason file that I've mentioned a couple of times already.

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Jason stands for javascript object notation and it's quite a common file format.

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It's not the easiest to work with but it is doable and it's not that complex.

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And python has built in support for parsing those files and for saving those files.

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So it's rather convenient file from a free to use for our case

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here.

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You see a high level overview of what that file looks like if curly braces want to open

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one to close the file and within the curly

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braces you have what is basically a python dictionary.

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So it's a name between quotes and that name has a value

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in this case

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it is another dictionary.

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So here we say these are our collections and we want to have to collections.

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We want to have rocks and we want to have plants

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And within each

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we say link which will contain a list of files and prefixes

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that we want to link into the scene into this collection.

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So here you see a list of things. It has the same notation as python.

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So with these blocky parentheses kind of things.

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And within it we have a list of in this case to dictionaries.

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Again,

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each dictionary has a file and it has a prefix

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of all the collections to link in from that file.

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We do something similar for the plants.

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We have a link and then again file, prefix file, prefix file,

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prefix in this case there are three of them.

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Even

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now we could have removed this link and put this information directly into plants.

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But I I always like to have things a little bit

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more explicit and this will also give you a chance later.

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If you want to add something extra to it.

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Maybe uh maybe you want to have something visible but default or not or maybe you

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want to enable only in certain view layers or not by having this under a link.

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K.

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You can add multiple keys later for your own workflow for now

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let's keep it simple and write some code that loads this file,

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then turns it into python data structure that we can use.

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So let's comment out these two lines.

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We'll just leave them sticking around as a reference for us. Later,

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first moved to load the Jason file and for that we need to have the Jason module.

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This is built into python so we can just do import Jason and then we have access to it.

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I think it's a nice touch to have the Jason file sitting next to the blend file,

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which means that we want to write it in slash slash notation,

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which means we have to translate the file first.

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This can be done by passing the slash slash ss dot Jason file name

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through the pilot passed its path

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and this will take care of that.

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So now all we need to do is open the file and feed it to the Jason library.

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I will be copy pasting some code instead of typing at all because now

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we have a lot of python code that will do auto completion and show

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information pop ups and everything because I scaled up my editor for this video

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is going to block a lot of things and be more distracting than anything.

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So this is how you open a file,

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you can say with open Jason file name as in file

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and this will open the file for reading

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and once the with statement is done it will close it again,

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making sure that we don't leave any open file handles around online.

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This is not such an issue,

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but on Windows is a problematic because if the file is opened by one program,

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another program won't be able to read or write to that file,

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you won't even be able to delete the file.

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So always make sure that you close a file after you have opened it.

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And the with statement is a perfect way to do that.

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After we've opened the file

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we can pass it to Jason download which takes a file as the first parameter.

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And this will load the file and parse it into a python data structure.

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This means that link info here is a dictionary.

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00:21:03.990 --> 00:21:08.000
If you want to see exactly what in there you can use a print statement, run the code

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and then you can see for yourself.

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So going back to our Jason file we know that it represents

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a dictionary with one key called collections which contains another dictionary.

394
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So let's see how we access this in python.

395
00:21:21.370 --> 00:21:23.050
You would take the link in for dick.

396
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We get the key collections and we can loop over this by taking key value pairs

397
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and for this we use the dot items function

398
00:21:31.600 --> 00:21:36.060
dot items on the dictionary gives us something that we can loop over with a for loop

399
00:21:36.440 --> 00:21:39.520
and it will get you paris of the key and the value

400
00:21:39.870 --> 00:21:43.550
in our case it will give us rocks with that dictionary.

401
00:21:44.140 --> 00:21:46.660
And then pants with the 2nd dictionary.

402
00:21:47.240 --> 00:21:50.260
So call name is first rocks and call info is it's

403
00:21:50.260 --> 00:21:53.770
dictionary and then on the second iteration call name is plants

404
00:21:53.970 --> 00:21:56.270
and then call info is the plants dictionary.

405
00:21:56.740 --> 00:22:01.270
So the first thing we have to do is ensure that this collection actually exists.

406
00:22:02.440 --> 00:22:05.560
We have a function for that. So let's move that code

407
00:22:06.600 --> 00:22:07.660
and put it here.

408
00:22:08.340 --> 00:22:11.590
And instead of having environment as art coated collection,

409
00:22:11.660 --> 00:22:14.460
we of course take the collection name from the Jason file.

410
00:22:15.660 --> 00:22:18.800
Now might also be a good time to just save your file.

411
00:22:18.820 --> 00:22:23.350
Reloaded in blender and see that it actually creates those collections for you.

412
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Just as a first step to see that that is working.

413
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And also run it twice to see that it still works when the collections already exist.

414
00:22:31.340 --> 00:22:33.590
So the next thing we have to do is take a look

415
00:22:33.590 --> 00:22:36.460
at that link key and the list that is in there.

416
00:22:37.040 --> 00:22:39.670
So calling for link will give us this list

417
00:22:41.840 --> 00:22:44.670
and of course because it's a list we can just loop over it

418
00:22:44.680 --> 00:22:47.750
and it will give us that dictionary with a file and a prefix.

419
00:22:47.870 --> 00:22:50.360
Let's make it a little bit easier for us and

420
00:22:51.340 --> 00:22:56.670
take the file and the prefix keys and store their values in these variables.

421
00:22:57.340 --> 00:23:00.270
So for the first iteration, foul path will be

422
00:23:00.640 --> 00:23:01.360
this path

423
00:23:02.940 --> 00:23:04.770
and this prefix will be

424
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this prefix

425
00:23:08.140 --> 00:23:11.050
what is left now is to link everything to the scene.

426
00:23:12.840 --> 00:23:15.770
But instead of using her heart coated file path

427
00:23:17.380 --> 00:23:21.350
we take the file path from adjacent file and the same for the prefix.

428
00:23:22.940 --> 00:23:25.080
Now we have to make sure that the white location

429
00:23:25.080 --> 00:23:28.120
is increased and not everything ends up at Y0.

430
00:23:28.130 --> 00:23:32.170
So we can do the same thing for this as we've done before with the explication.

431
00:23:34.940 --> 00:23:40.800
We can start location Y at zero and then passed it here. After this is done.

432
00:23:40.800 --> 00:23:45.720
All we need to do is increments the wild location with the step size and that's it.

433
00:23:45.740 --> 00:23:47.770
Let's go back to blender and see it in action.

434
00:23:49.520 --> 00:23:52.450
Let's delete everything there was including the collection

435
00:23:57.240 --> 00:24:00.960
and there it is. We have rocks, we have plants

436
00:24:03.740 --> 00:24:08.270
and everything is there in the file for you to start dressing up your set.

437
00:24:08.840 --> 00:24:10.270
Now this one final touch

438
00:24:10.700 --> 00:24:13.720
let's say the asset files change and something new was added.

439
00:24:13.950 --> 00:24:16.750
This is not automatically loaded into this file.

440
00:24:16.820 --> 00:24:20.170
If we rerun the operator again, it will create all the empties again.

441
00:24:20.180 --> 00:24:22.840
Including the ones that already exists in the file.

442
00:24:22.890 --> 00:24:25.380
That's at a little filter to the creation of the empties

443
00:24:25.430 --> 00:24:27.920
so that her coat doesn't try to recreate an empty.

444
00:24:27.920 --> 00:24:29.060
If it's already there

445
00:24:29.440 --> 00:24:32.940
for this we have to go to the link to seen function linking things

446
00:24:32.940 --> 00:24:36.970
that are already linked is fine blender will skip these automatically for us.

447
00:24:36.980 --> 00:24:40.660
So it really only the creation of the empties that we need to worry about.

448
00:24:41.240 --> 00:24:43.570
So here we are at the line that creates a new empty.

449
00:24:43.580 --> 00:24:47.190
So before this we want to have our check this I think is a nice approach.

450
00:24:47.200 --> 00:24:50.580
The collection name is going to be used as the empty name as well.

451
00:24:50.590 --> 00:24:54.450
So if the collection name already exists in linked to the objects,

452
00:24:54.450 --> 00:24:57.260
we know that the empty is already there and we can just keep it

453
00:24:58.240 --> 00:25:03.250
so I'll move this as a way. So we should not see anything new. Pop up here.

454
00:25:03.260 --> 00:25:05.890
And of course you can also see it here in the outline

455
00:25:05.890 --> 00:25:08.140
er that these numbers shouldn't increase

456
00:25:08.140 --> 00:25:09.960
because everything has already been loaded

457
00:25:14.240 --> 00:25:16.270
there. You have it it all works fine.

458
00:25:17.140 --> 00:25:19.780
So this is it for this episode of scripting for artists.

459
00:25:19.900 --> 00:25:23.250
Of course this is just the start but you can imagine that

460
00:25:23.260 --> 00:25:27.610
things get pretty powerful when you can store information into adjacent file,

461
00:25:27.620 --> 00:25:31.410
load that into blender and use that to insensate certain collections.

462
00:25:31.420 --> 00:25:34.860
Of course collections can also consist of links collections.

463
00:25:35.040 --> 00:25:38.610
So the set that you're building with this tool can also be

464
00:25:38.610 --> 00:25:41.960
a collection that you instantly eight into a shot file for example.

465
00:25:42.140 --> 00:25:45.900
So I'll leave that up to your imagination and your workflow for now.

466
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This is it If you have any questions or comments,

467
00:25:48.320 --> 00:25:50.560
leave them below and I will see you soon