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Bigger Backpacks

0.8.1.9

Info

This guide was initially written by DrStalker on Reddit and rewritten to fit this documentation's format.

This guide assumes you're familiar with the basics of modding Stoneshard.
If that's not the case, try reading the Getting Started guide first.

Description

In this article we're going to take the very limited backpacks of the game and make them a bit more convenient to use, first by changing their size in the inventory and then by changing their capacity.

This guide is a bit more advanced than the example in Getting Started, so make sure to read thoroughly.

Identifying the assets

Since we're working with a gameobject, we need to identify the assets related to backpacks and figure out what they do.

1. Identifying the backpack gameobjects
Screenshot - Search for backpack

UMT_SEARCH

As seen in the screenshot above, when searching for backpack in UMT, we get a few gameobjects :

  • o_loot_backpack, this is the the backpack when on the ground.
  • o_inv_backpack, this is the backpack when in your inventory.
  • o_container_backpack, this is the GUI that shows up when you open the backpack.
2. Identifying the backpack sprites

When we searched backpack in UMT, we also seem to have found a few sprites.
But how do we know which ones are of interest to us ?

Double click on the gameobjects we've identified above and simply check their Sprite field !

Screenshot - Finding the Sprites

UMT_SPRITES

Now we know which sprite is used by the gameobjects we found :

  • o_loot_backpack -> s_loot_travellersbackpack
  • o_inv_backpack -> s_inv_travellersbackpack
  • o_container_backpack -> s_container_backpack

Changing the size in the inventory

Now that we know what gameobjects and sprites to look at, we can get to work.
Since we're trying to modify the backpack in the inventory, we know that there is a good chance we will have to modify o_inv_backpack, s_inv_travellersbackpack or both.

Quick Theory - Inventory Cell Size

As we are going to deal with an inventory sprite (s_inv_*...), there's a very important thing to know.

Each cell in your inventory is exactly 27x27 pixels.

But why is that important ?

Because Stoneshard doesn't set a value for how many cells an item is going to take in your inventory anywhere.
The game decides this solely based on the size of your sprite.

Here are some good examples :

  • ✅ A sprite which is 27x27 pixels will be 1 cell wide and 1 cell tall. (Example : s_inv_coal)
  • ✅ A sprite which is 54x27 pixels will be 2 cells wide and 1 cell tall. (Example : s_inv_clay_plate)
  • ✅ A sprite which is 27x81 pixels will be 1 cell wide and 3 cells tall. (Example : s_inv_footmanaxe)

Here is a bad example :

  • ❌ A sprite which is 33x27 pixels will not fit in a single cell and overflow on its neighbour horizontally, but fit perfectly vertically.

Info

In short, just make sure your inventory sprite is always a multiple of 27.
If it's not, don't panic, you can always add padding to it to make it a multiple of 27.

Changing the Size - Part 1

Let's take a quick look at s_inv_travellersbackpack.

Its dimensions seem to be 81x108 pixels.
As we know a single cell is 27 pixels, we can deduce the resulting item will take 3x4 cells in the inventory.

Notice something weird about the sprite itself ?

If you answered something like :

Wait isn't there a lot of padding ?

You'd be correct.
If you didn't, it's fine, I swear, I'm not crying you are.

As a matter of fact, if you export the sprite by pressing the Export all frames (or Spine data if this is a Spine sprite) button, you'll notice the sprite itself is actually...

47x75 pixels !

But wait those are not multiples of 27 !

That's absolutely correct, but it's close !
If we were to try to use multiples of 27 to make it fit in the inventory cells, the closest we could get would be 54x81 pixels, which would mean 2x3 cells in the inventory, so let's try to go for that.

The reason why the sprite itself not using multiples of 27 is fine is because it's using padding to reach them !
In the next section we'll see how to get rid of some of that padding to get our desired 54x81 pixels sprite.

Changing the Size - Part 2

First let's change the size of s_inv_travellersbackpack to 54x81.
We'll also reduce the margins to 1, 53, 80 and 1.

Screenshot - Editing Size and Margins in s_inv_travellersbackpack

UMT_MARGIN

Now let's middle mouse click on PageItem 2333 (UndertaleTexturePageItem).
(Alternatively, you can also double click it or even click the ... button on the right.)

Once on the PageItem for the backpack, let's change the position and bounding box size for the backpack to those in the screenshot below :

Screenshot - Editing Position and Bounding Box in PageItem 2333

UMT_POSITION

Wait, what did we just do ?

I won't go into too much detail here but essentially :

  • We changed the size and margins (padding) of the sprite in s_inv_travellersbackpack.
  • Then we changed the size and position of the texture the sprite uses in PageItem 2333.

Now that this is done, let's save our .win file.

Info

If you already have a backpack you can load up your save and test your changes.
You might need to move the backpack in your inventory or drop it on the ground and pick it up for the change to take effect, as it was saved using the original size and not the new one.

Spawning the backpack

Having a nice backpack that fits into a 2x3 space in your inventory is fine, but what if you don't have a backpack in your save ?
How do you test your changes ?

By spawning one out of thin air, obviously.

Spawning the backpack

If you've read the Getting Started article, you already know half of how to achieve this.
We're going to use the player's F4 KeyPress event in order to spawn the backpack !

  • First, let's search for o_player and find the player's gameobject.
  • Once that's done, scroll down to the KeyPress events, and locate the vk_f4 line.
  • Then, simply double click on the gml_Object_o_player_KeyPress_115 script to open it.
  • This should open an empty code editor.
Screenshot - Locating o_player's KeyPress Events

UMT_POSITION

Now that we're in the code editor, let's write the following : 

with (o_inventory)
    scr_inventory_add_item(o_inv_backpack)

What's that command ? How does it work ?

Check the Useful Functions article to learn more.
Alternatively, you can middle mouse click it to check out its code !

Save your .win file, load up your save, hit F4 and you should get a shiny new backpack, which only takes 2x3 cells in your inventory.

Reminder

If you intend to share this mod, don't forget to remove the code we added in this section before creating your .xdelta file.
If you don't, anyone will be able to spawn backpacks with the F4 key !

Changing the capacity

Now that we have a backpack we can spawn and that takes 2x3 cells in the inventory, let's see how to make it even better by holding more space.

1. Changing the UI

In theory, we could make an entirely new texture or expand an existing one.
But for the sake of simplicity and to save some time, we can just reuse an existing asset as is.

We're going to reuse s_container, which is the sprite used for chests, wardrobes (etc.).

Screenshot - Container Sprite

CONTAINER_SPRITE

First, let's find o_container_backpack and open it.
Now, we're going to change its sprite from s_container_backpack to s_container.
To do this, simply search for s_container in UML and drag it over the current one.

Screenshot - Changing the Sprite

UMT_POSITION

2. Adjusting the Code

Unlike inventory items, the capacity of containers (chests, wardrobes, backpacks...) is defined in the code and not simply based on the sprite's size.

If we take a quick look at o_backpack_container, the only script it seems to have is gml_Object_o_container_backpack_Other_10.
Let's open it by middle mouse clicking or double clicking it.

We're going to replace the existing code with our own :

gml_Object_o_container_backpack_Other_10
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event_inherited()
closeButton = scr_adaptiveCloseButtonCreate(id, (depth - 1), 229, 3)
with (closeButton)
    drawHover = 1
getbutton = scr_adaptiveTakeAllButtonCreate(id, (depth - 1), 230, 27)
with (getbutton)
    owner = other.id
cellsContainer = scr_guiCreate(id, o_guiContainer, depth, adaptiveOffsetX, adaptiveOffsetY)
cellsRowSize = 7
scr_inventory_add_cells(id, cellsContainer, cellsRowSize, 5, true)
What does this code do ?

This code is responsible for creating the GUI element when the backpack is interacted with.

We first changed the positioning of the Close and Take all buttons to match our new sprite.
Then we changed the values for how many cells this container now holds.

As usual, now we save our .win file and test our changes.
Your backpack should now use the container sprite instead of its usual one and it should have 7x5 cells to store your items in.

Tip

If you had items in your backpack beforehand, it's possible they now overlap each other.
You can fix this by taking them out of your backpack and picking them up again.

Distributing your mod

See Creating Mods in the DeltaPatcher article.