Costumes

Author(s): benevolusgoat, catinsurance
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Crash course table of contents

The crash course is still a work in progress!

1. Creating a mod.
   1. Creating the mod.
   2. Uploading a mod.
2. Creating a passive item.
3. Creating an active item.
4. Adding to item pools.
5. Making costumes.
6. Making a new character.
7. Creating entities.
   1. Entity basics.
   2. Creating effects.
   3. Creating enemies.
   4. Creating a familiar.
8. Adding sounds.
9. Adding music.
10. Making pocket items.
    1. Creating custom cards, runes, and objects.
    2. Creating custom pills.
11. Creating challenges.
12. Structuring your mod.
13. Conclusion.

Costumes are the extra layers of sprites that are added onto Isaac to change his appearance. Costumes can be given from items, characters, and even directly under some circumstances. This tutorial will cover how to create and add your own custom costumes.

Video tutorial

Creating a costume

All costumes require a .anm2 file. When creating your costume, it is easiest to reference, copy, or modify an existing costume from the game, as it will already have all the layers and frames laid out for you. For example, if you're trying to make a costume that gives Isaac a hat, you could reference something like Black Candle's costume (located in resources/gfx/characters/260_blackcandle.anm2). You can find costume .anm2 files inside resources/gfx/characters/ after extracting the game's resources.

Each animation in a costume corresponds to an animation in the player .anm2 file (resources/gfx/001.000_player.anm2). Each keyframe in this animation corresponds to that keyframe of the player. For example, if creating a costume that affects Isaac's body, you will want to create animations for each directional walk animation in the player .anm2 file, and copy the keyframes from those.

Costume layers

All of the game's costumes work via layers. A costume can occupy one or more layers, though each layer can only hold one spritesheet at a time. There are a total of 15 layers, although mods can only use 13 of these. Additionally, there is a set order of when each layer is rendered. Below is the list of layers that mods can use in order of render priority, from being rendered first to last (layers rendered first will appear behind layers rendered last):

Layer render priority

Layer name	Description
glow	Rendered behind the head. Used for glowing auras, such as with items like Mysterious Liquid
body	Directly replaces Isaac's body
body0	Rendered over the body
body1	Rendered over the body
head	Directly replaces Isaac's head
head0	Usually character-specific costumes (e.g. Magdalene's hair)
head1	Rendered over the head
head2	Rendered over the head
head3	Rendered over the head
head4	Rendered over the head
head5	Rendered over the head
top0	Used for wing costumes when walking upwards. Attached to the body's direction, but renders above the head
back	Attached to the head. Exclusively used by the Venus costume for the back view of the hair. Best seen with a costume that removes the body

You can find a spreadsheet documenting every costume and the layers they occupy by clicking here.

A costume can have any combinations of these layers. Any layers not a part of this list will not appear on Isaac.

If two costumes that occupy the same layer are added onto Isaac, only the one with the highest priority will be rendered. If two costumes of equal priority occupy the same layer, then only the one that was added most recently will render. Priorities are defined in the costumes2.xml file.

If a costume with more than one layer has one of its layers conflicting with another costume and is of the lower priority, the other layers will still be rendered, allowing for a unique mismatch of different sprites on multiple layers.

Animated costumes

Animated costumes can be done by adding _Idle after the animation name. The animation restarts from the first frame when switching to a different animation (e.g. HeadRight_Idle to HeadDown_Idle). Make sure to check the loop box at the bottom of the animation editor in order for your animation to loop. Standard layer rendering priority still applies, so you can have an animated head0 layer while having a static head4 layer.

You can also add _Overlay after the animation name to animate on top of the player's animation instead of replacing it. For example, HeadDown_Overlay animates on top of the player's HeadDown animation, while HeadDown_Idle replaces the player's HeadDown animation.

Some costumes, like the second form of the Wavy Cap costume (resources/gfx/characters/029x_wavycap2.anm2), have both an overlay and an idle animation.

Adding a costume

All costumes entries are defined in a costumes2.xml file, located in the content folder at the root of your mod folder. In this folder, there must be a root costumes tag. This tag has an anm2root property, which should point to the root directory of where your costumes are stored, usually gfx/characters/.

<costumes anm2root="gfx/characters/">

</costumes>

When defining a costume inside of a costumes root tag, your costume is required to have at least a anm2path property and a type property.

• The anm2path tag holds the path to your costume, starting from the anm2root property in the root costumes tag.
• The type tag tells the game what type of costume you're creating. There are 5 types of costumes:
  • passive costumes will be added when a passive item is added to Isaac's inventory (after Isaac is done holding it over his head), and will be removed automatically if the passive item is lost.
  • familiar costumes function the same as passive costumes, but for items defined as familiars in items.xml.
  • active costumes will be added when an active item is used, and will be removed automatically upon entering a new room.
  • trinket costumes will be added when a trinket is added to Isaac's inventory (after Isaac is done holding it over his head), and will be removed automatically if the trinket is dropped.
  • none costumes are known as "null costumes", and must be applied manually through code.

<costumes anm2root="gfx/characters/">
    <costume anm2path="some_passive_costume.anm2" type="passive" />
    <costume anm2path="some_familiar_costume.anm2" type="familiar" />
    <costume anm2path="some_active_costume.anm2" type="active" />
    <costume anm2path="some_trinket_costume.anm2" type="trinket" />
    <costume anm2path="some_null_costume.anm2" type="none" />
</costumes>

Applying null costumes

To apply a null costume, you must get its ID using Isaac.GetCostumeIdByPath("filePath"), and apply it on the player with EntityPlayer:AddNullCostume(costumeId).

Additionally, Isaac.GetCostumeIdByPath will return -1 if the costume's path isn't defined in costumes2.xml. Attempting to add a costume with an ID of -1 or any ID that doesn't correlate to an existing costume will cause the game to crash.

-- At the top of your Lua file...
local costumeId = Isaac.GetCostumeIdByPath("gfx/characters/some_null_costume.anm2")

-- Somewhere else in your code...
local player = Isaac.GetPlayer(0)
player:AddNullCostume(costumeId)

There are some additional properties you can add to your costume tag for extra customization.

• priority defines the priority of the costume if it were to have a layer than conflicts with a different costume's layer (see costume layers).
• overwriteColor defines if a costume should override the player's skin color with the skinColor property.
• skinColor defines the id of the skin color that the player's skin will be changed to.
• hasSkinAlt defines if a costume has alternate spritesheets depending on the skin color of the player. These spritesheets should be in the same folder as the original spritesheet, but with a different suffix to its file name. This suffix correspond to the skin color the spritesheet is for. The skin colors are _black, _blue, _green, _grey, _red, and _white (example: a spritesheet at gfx/characters/costumes/face.png, with an alternate spritesheet for the red skin color at gfx/characters/costumes/face_red.png).
• forceBodyColor defines if a costume will always force the body color to be the defined skin color.
• forceHeadColor defines if a costume will always force the head color to be the defined skin color.
• isFlying defines if the costume is meant for something that grants flight.
• hasOverlay defines is a costume is using an overlay effect, also known as an animated costume.

Adding a character-specific costume replacement

Some characters have unique head shapes or faces, and may require alternate spritesheets for certain costumes in order to make them look natural. These character-specific variants are added through costume suffix folders.

Inside your costumes folder (usually resources/gfx/characters/), you can create a folder that houses these costumes for your character. The folder should start with the name "costume_", and end with a suffix defined in players.xml. Either define costumeSuffix in your character's players.xml entry (e.g. costumeSuffix="mycharacter"), or use an existing suffix from the vanilla characters. The complete folder name should look something like "costumes_mycharacter". For reference, the existing vanilla suffixes are:

• shadow (Dark Judas, Tainted Judas)
• lilith
• keeper
• apollyon
• forgotten
• forgottensoul
• lilithb

Within your costume suffix folder, place your alternate .png file with the exact same name as the spritesheet you wish to replace. The game will automatically use this spritesheet instead of the default one.

Adding a character-specific costume

Custom characters use a costume in order to have a different default appearance than Isaac. For example, Cain has a costume for his eyepatch. There are 3 ways to add a costume such that it will only appear on your own custom character.

Lua

As mentioned earlier, you can set up your costume to be a null costume and add it through code. You can add your costume under the MC_POST_PLAYER_INIT callback for when your player initializes, and for extra safety, on MC_POST_NEW_ROOM in case it was accidentally removed.

Warning

Costumes added this way are not protected from being removed by the Mother's Shadow escape sequence, or by things which reroll your items, such as the D4.

local mod = RegisterMod("My Mod", 1)
local MY_PLAYER = Isaac.GetPlayerTypeByName("My Character", false)
local MY_COSTUME = Isaac.GetCostumeIdByPath("gfx/characters/my_costume.anm2")

function mod:AddPlayerCostume(player)
    --Check by PlayerType, not name, to ensure it's our character
    if player:GetPlayerType() == MY_PLAYER then
        --Add the costume
        player:AddNullCostume(MY_COSTUME)
    end
end

function mod:AddCostumeOnNewRoom()
    --Most reliable way to search through players in the room
    for _, ent in ipairs(Isaac.FindByType(EntityType.ENTITY_PLAYER)) do
        --Isaac.FindByType passes an Entity. Turn it into an EntityPlayer to use player-specific functions
        local player = ent:ToPlayer()
        --Call the function above that already has the code we want
        mod:AddPlayerCostume(player)
    end
end

--The 0 here is for actual players, so not co-op babies, but still including co-op ghosts
mod:AddCallback(ModCallbacks.MC_POST_PLAYER_INIT, mod.AddPlayerCostume, 0)
mod:AddCallback(ModCallbacks.MC_POST_NEW_ROOM, mod.AddCostumeOnNewRoom)

XML (Non-REPENTOGON)

Using XML to add a costume will ensure it will never be removed by rerolls, or by the Mother's Shadow escape sequence. Vanilla characters get around this by adding a costume property with the ID of the costume that the character should have. Because modded costumes do not have IDs, the only solution to this is to use one of vanilla game's player-specific costumes that has the appropriate layers we need, and to replace its spritesheet in our character's costume suffix folder.

Inside the players.xml file where you have your custom character defined, add the costume property and set it to an existing vanilla null costume. You can get a good idea of the IDs of each null costume through the NullItemID enumeration, or by looking in the costumes2.xml folder inside the game's extracted resources.

In this example, we will make a custom costume for our character's hair that uses Flipped Tainted Lazarus' costume as a base, as this costume is never added to other characters in the game through normal means.

<players root="gfx/characters/costumes/"
         portraitroot="gfx/ui/stage/"
         nameimageroot="gfx/ui/boss/">
    <player name="My Character" skin="character_mycharacter.png"
            hp="6"
            nameimage="playername_mycharacter.png"
            portrait="playerportrait_mycharacter.png"
            costume="34"
            costumeSuffix="mycharacter"
            birthright="???" />
</players>

Next, we'd create an alternate spritesheet based off of resources/gfx/characters/character_009b_lazarus2hair.png, and put that in our costumes suffix files (e.g. costumes_mycharacter).

XML (REPENTOGON)

REPENTOGON adds a method to add your own costume through the modcostume property you can add to your character inside players.xml.

First, define a null costume in costumes2.xml. Unlike for normal null costumes, you'll need to set an ID! This will not overlap with IDs from costumes of other types (passive, familar, active, trinket), or from other mods.

<!-- costumes2.xml -->
<costumes anm2root="gfx/">
    <costume id="0" anm2path="characters/some_null_costume.anm2" type="none" />
</costumes>

Then, add modcostume to your character's players.xml entry, and set it to the ID you defined for the costume.

<!-- players.xml -->
<players root="gfx/characters/costumes/"
         portraitroot="gfx/ui/stage/"
         nameimageroot="gfx/ui/boss/">
    <player name="My Character" skin="character_mycharacter.png" hp="6"
            nameimage="playername_mycharacter.png"
            portrait="playerportrait_mycharacter.png" modcostume="0"
            birthright="???" />
</players>

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