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Modding Questions and Answers

If there's something you want to learn how to do that i dont have a tutorial for and you can't figure out from vanilla's code, feel free to join my discord server to ask me. This page is a collection of information I've given people on that server so you can search it more easily. It will only be helpful if you're already comfortable with Java! These answers are for a mix of versions so you will have to do some translating but they should point you in the right direction.

I might add an index and split it into seperate pages to help the SEO at some point if i feel inspired

how scale and translate text on a gui?​

QUESTION: I’m using posestack.scale for the scale and just manually tweaking some math for the x and y to get it to look okay. It works but I’m thinking there must be a better way to translate the positions when doing non standard scales like 0.8**

the thing that makes it weird is that when you scale the matrix it scales any translations you've done as well, including the position you told the text to be at. so really what you want is to draw the text centred at (0,0), then scale it, then translate it to where you actually want it. tho calling the translate/scale methods will move everything, not just the text you're trying to work with. it might work if you,

  • PoseStack#pushPose
  • render text centered on 0,0 (you'll probably need to check the width and height of the component since i'm guessing you pass in the top left coordinate when you render it)
    • the Screen class has a this.font variable you can use (it gets it from Minecraft.getInstance().font). can do this.font.draw(poseStack, Component.literal("words"), x, y, 0xFFFFFF);
  • scale it
  • translate to real position
  • PoseStack#popPose and wrap that up into a method that lets you render whatever text at whatever position at whatever scale

is it a problem to override depreciated methods on Block/Item?​

the depreciated warning istelling you that if you ever need to call that method, you should call it from the blockstate/itemstack instead but if you're making your own block/item you do have to override it on the block/item singleton class itself

what are the parameters of the Slot constructor (for inventory menus)? and how does the slot know how big to be in the gui?​

  • Container/Inventory: the container of items the slot should mondify
  • index: the container has a list of itemstacks. this is the index in that list that the slot represents. used when Container#getItem, Container#setItem, and Container#removeItem are called by the Menu
  • x: the x coordinate of the top left corner of the slot's square on the gui
  • y: the y coordinate of the top left corner of the slot's square on the gui

you'll notice you dont have to pass in the width/height because all slots are a square of a set size (you'll notice that all the slots in vanilla inventories are the same size).

what do i do instead of the genIntellijRuns gradle task if i want to use vscode​

you dont have to do the generate runs thing, its just a convince thing for the intellij/eclipse people to run the game from within the ide. can just use gradlew runClient from the command line when you want to run the game other than that, should be exactly the same as long as you can figure out how to make vscode import a gradle project on your own (there is a plugin for it)

i was following one of your tutorials and dont have one of the packages you mentioned​

the packages are just for organization, doesn’t actually matter, you can just make it if you feel inspired. please learn java more, ty!

you say to copy a class from vanilla (ie. tool Tiers or ArmorMaterials), how do i see vanilla classes?​

in intellij you can press shift twice to search through vanilla classes (theres a little check box in the top right that says “include non project items” or something that you should click so its not just searching your code), im sure eclipse/vscode can do it to but idk the keyboard shortcut

also, if you're looking at a reference to a vanilla class/method, you can "Go To Declaration", generally by holding command/control and clicking on it

how do i make a geckolib animation sync with an attack​

geckolib has a pretty good wiki (https://github.com/bernie-g/geckolib/wiki/Home) for the details of making animations play at all. for an attack animation specificly, you'd have a dataparameter on your entity that syncs an int from server to client and then when your attack starts you set that to the length of your animation (in ticks) and decrement it every tick until its 0 and check it on the client (in your animation predicate) to play your animation while its ticking down. my mimic mod has an example you can look at https://github.com/LukeGrahamLandry/mimic-mod (look in the MimicEntity and MimicAttackGoal classes)

how do i make the dev environment work on apple silicon for 1.12​

absolutly no clue. deal with the slowness of roseta 2 emulating it or upgrade to a version of minecraft from not 5 years ago i guess. if you happen to figure it out, please tell me how and i'll document it here

how do i make my tile entity save its nbt data when you break the block and place it down again?​

can look at how shulker boxes do it. this is their loot table https://github.com/InventivetalentDev/minecraft-assets/blob/1.18.2/data/minecraft/loot_tables/blocks/shulker_box.json and ShulkerBoxBlock overrides getDrops to set a tag through that loot table in a complicated way
but i think you should be able to just override getDrops to return a list of just an item stack of the block with whatever data written to the tag

when i create a FluidTank from my block entity (for capability), what do i pass into the validator?​

the validator is just a predicate for which fluids its allowed to store. so like if you want it to store any type of fluid just use (f) -> true, or if it should only store water that would be (f) -> f.getFluid().is(FluidTags.WATER) and i think thats like if it is ever allowed to store that type of fluid so dealing with like limiting it to a certain capacity is handled separately

my data gen isnt working​

make sure you are running the gradle runData task (ie ./gradlew runData from the terminal)

why does calling forceAddEffect crash?​

LivingEntity#forceAddEffect only exists on the client so if you try to call it from server/common code, it will crash. instead, you should always call LivingEntity#addEffect, preferably only on the server side (check that !level.isClientSide()) and let minecraft sync it to the client on its own

how do i make a bunch of versions of the same item but change the colour of part of the texture (like leather armor or spawn eggs)​

theres a whole thing for having a greyscale overlay texture and then tinting it. its like the one thing forge docs have lol https://mcforge.readthedocs.io/en/1.16.x/models/color/ thats for 1.16 but i think it should be the same.

you can store which colour it should use in the item stack's nbt tag and read it back when the game wants to apply the tint so you dont need lots of different items. you can also have different layers of texture, defined in your model json file, if you only want to tint part of the texture a certain colour

for doing something that tints based on the biome colour (like grass and leaves) look at the vanilla code for how it gets that biome's colour in BlockColors#createDefault which calls GrassColors#get

how do i replace my arrow render with a blockbench model​

not something i know of a specific tutorial for but i can give general instructions if you're quite comfortable with java. (its pretty much the same as giving any entity a custom model if you can find a tutorial for that except you can't use a LivingEntityRenderer since your arrow isnt a LivingEntity)

  • make sure the bb model is in the Java Modded Entity project type
  • export it as a java class & import all the packages it needs
  • have an EntityRenderersEvent.RegisterLayerDefinitions event listener and call event.registerLayerDefinition(YourModelClass.LAYER_LOCATION, YourModelClass::createBodyLayer); (specificlly 1.17+)
  • create a renderer class that renders your new model instead of the arrow one. its render method would call renderToBuffer on your model.
  • bind that renderer to your arrow entity type in FMLClientSetupEvent as befor

i want to make an entity's health configureable but it doesnt sync when i update the config file (it only syncs when the game restarts)​

if just got the config value on the EntityAttributeCreationEvent or whatever where you bind the base attributes to the entity type, thats not gonna work because that event happens once at the beginning when entity types are registered, it's not called for every entity. to make it actually update live with the config you'd have to have all the entities checking if it changes and applying attribute modifiers to their health to get it to the right value

how can I increase the melee attack range for a vanilla mob​

mixin to MeleeAttackGoal#getAttackReachSqr

how do I check what dimension a player is in?​

player.getLevel().dimension() gives you a ResourceKey<Level> which can be compared to Level.OVERWORLD, Level.NETHER, Level.END, etc

how can i make sleeping skip night in another dimension​

I it seems to be handled by the SleepStatus class which players are added to in ServerPlayer#startSleepInBed only if the dimension type has natural set to true but you could probably add people on your own. and then ServerLevel#tick checks the doDaylightCycle game rule and sets the time to day if SleepStatus thinks enough people are sleeping. so maybe some mixins somewhere in there could do what you want. idk if that helps at all 🤷. There's also a PlayerSleepInBedEvent but i think it mostly lets you block sleeps, not allow them

im looking to make a custom furnace but i do not know where to start​

Look at how vanilla furnaces work. Basiclly, make a tile entity that holds items and crafts things every x ticks, bind a container/screen to it so you can put in items, decide how you want to deal with recipes (hard code them or make your own recipes type and use json files)

how do i make my projectile render like an item​

you could extend ProjectileItemEntity or just impliment IRendersAsItem and then when you bind a renderer to your entity type, you would do RenderingRegistry.registerEntityRenderingHandler(EntityInit.PUT_NAME_HERE.get(), (m) -> new SpriteRenderer<>(m, Minecraft.getInstance().getItemRenderer()));

why am i getting a "player moved wrongly" error​

instead of calling player.setPos(...), try ((ServerPlayerEntity)player).connection.teleport(x, y, z, player.yRot, player.xRot, EnumSet.noneOf(SPlayerPositionLookPacket.Flags.class)) (make sure to do it in the if block that checks !isclientside). thats what the teleport command uses

my custom cactus block just breaks when it grows​

If you made your cactus based on the vanilla CactusBlock, it breaks if the canSurvive method returns false. vanilla has that method call canSustainPlant on the block state below it, so you should make sure that your plant is a valid block for your plant to grow on. You can do that by overriding canSustainPlant on your custom cactus block and returning true if the state passed in is of your plant. I think this would work, 

@Override
public boolean canSustainPlant(BlockState state, IBlockReader world, BlockPos pos, Direction facing, net.minecraftforge.common.IPlantable plantable) {
    BlockState plant = plantable.getPlant(world, pos.relative(facing));

    if (plant.is(this)){
        return true;
    } else {
        return super.canSustainPlant(state, world, pos, facing, plantable);
    }
}

my custom sugarcane/cactus blocks just continues to grow instead of stopping at 3​

for the sugar cane, i would think using the same randomTick method as vanilla's SugarCaneBlock would work. it seems to check that there's less than a 3 tall stack of your plant before growing so unless you changed the number in that for loop / took out the if statement, idk

how would i make a block drop xp like ores do?​

vanilla ones use the OreBlock class which just overrides this method (you can return whatever number you want. can give more based on fortune level but should give 0 if they have silk touch)

@Override
public int getExpDrop(BlockState state, net.minecraft.world.IWorldReader reader, BlockPos pos, int fortune, int silktouch) {
    return silktouch == 0 ? RANDOM.nextInt(7) : 0;
}

my non-cube blockbench modeled block makes ajacent faces of blocks not render properly​

minecraft's rendering system culls block faces it thinks are hidden. you need to tell it your block is not a full cube by calling RenderTypeLookup.setRenderLayer(BlockInit.YOUR_BLOCK.get(), RenderType.cutout()) on the FMLClientSetupEvent

any error with the phrase "not valid resource location"​

ResourceLocations cannot have spaces or capital letters

how to make a spawn egg for custom entity (forge deferred registers)​

since items are registered before entities, you should make your own verison of the SpawnEggItem class and override getType in such a way that you don't have to call .get() on your registry object before its registered

how do i make a pickaxe that destroys 3x3 area​

steal the logic from this https://github.com/Ellpeck/ActuallyAdditions/blob/main/src/main/java/de/ellpeck/actuallyadditions/common/items/ItemDrill.java (its MIT licensed) and port it to your MC version / mod loader

how can i fix NullPointerException that is produced when summoning my entity​

make sure you bind a renderer in the ClientSetupEvent and bind attributes (max health specificlly) on the EntityAttributeCreationEvent (like event.put(EntityInit.YOUR_ENTITY.get(), attributes))

how do i make an autosmelt pickaxe (or other conditional modification of lots of loot tables at once)​

use global loot modifers! they run whenever minecraft gets items out of a loot table

why doesnt the tick method on my block fire​

problem is that the tick method on blocks is for random ticks (https://minecraft.fandom.com/wiki/Tick#Random_tick) so its not called every tick. You also need to call randomTicks() on your Block.Properties to make it react to random ticks at all. To do something every tick you could have a tile entity (ive got a tutorial for that). if you just want a timer to do something a while after you place your block, it might be better to schedule a tick. if you do world.getBlockTicks().scheduleTick(pos, this, delay) in your onPlace method, it should call tick after <delay> ticks.

how do i make my item use the honey bottle gulping animation?​

the HoneyBottleItem has a method that specifies the animation to play while its being used

@Override
public UseAnim getUseAnimation(ItemStack pStack) {
    return UseAnim.DRINK;
}

and then theres a big switch statement that checks for that and renders it differently in ItemInHandRenderer#renderArmWithItem

how do i change the slipperiness of every block?​

You could use a mixin to change the return value of Block#getSlipperiness (there are two versions of that method with different parameters, should do both). Here's a good explanation of mixins: https://darkhax.net/2020/07/mixins

Alternatively, you could also use an access transformer to make Block#slipperiness public and then loop through every block and change the value after the blocks have been registered (ie. on FMLCommonSetupEvent)

how to do i make custom armor models (1.17+)​

my FMLClientSetupEvent isnt firing​

  • make sure the method is static
  • make sure the method has the @SubscribeEvent annotation
  • make sure the class has the @Mod.EventBusSubscriber(modid = ModMain.MOD_ID, bus = Mod.EventBusSubscriber.Bus.MOD, value = Dist.CLIENT). You must use Bus.Mod, NOT Bus.FORGE

how do i make key bindings?​

  • Create a keybind public static final KeyMapping OPEN = new KeyMapping("key.your_action_name", GLFW.GLFW_KEY_M, "key.categories." + ModMain.MOD_ID); somewhere
  • Call ClientRegistry.registerKeyBinding(YOUR_KEY); on FMLClientSetupEvent
  • checking YOUR_KEY.isDown() or YOUR_KEY.consumeClick() on KeyInputEvent should work. You'll have to send a packet if you want to react to it on the server side

What is the int parameter on Level#setBlock​

the third parameter is a flag about which block updates it should send. flags can be OR-ed (passing in 2 | 4 will have the effect of both)

  • 1 will cause a block update
  • 2 will send the change to clients
  • 4 will prevent the block from being re-rendered
  • 8 will force any re-renders to run on the main thread instead
  • 16 will prevent neighbor reactions (e.g. fences connecting, observers pulsing)
  • 32 will prevent neighbor reactions from spawning drops
  • 64 will signify the block is being moved

i think the fourth parameter is how many more layers of recursive block updates to allow. you can just use the version of the method that doesnt need this fourth parameter and just sets it to a reasonable default (512)

how do I make a mob say something in the chat when it is killed?​

There's an LivingEntity#onDeath method to override (make sure you still call the super of it) and then you can loop through world.getPlayers() and call player.sendStatusMessage(new TextComponent("hello world"), false)

how do i make an entity that has multiple textures?​

whatever resource location is returned by the getEntityTexture method in your renderer will be used as the texture. but theres only ever one instance of the renderer so you cant do the random in its constructor. you have to have the entity know which texture it should have, check that from the getEntityTexture method and return the appropriate ResourceLocation. Note that you'll want to save which texture it chose in its nbt data (override addAdditionalSaveData and readAdditionalSaveData) as well as use a EntityDataAccessor (previously called DataParameter) to sync the chosen texture from the server to the client (forge docs: https://mcforge.readthedocs.io/en/1.18.x/networking/entities/#data-parameters). You can look at vanilla's Cat code for an example.

does the order that deferred registers are used in the mod's constructor matter?​

nope, the whole point is that forge magically does it at the right time for you.

how to make an item appear with blue letters under the name like a potion​

look at the PotionItem#appendHoverText which calls PotionUtils#addPotionTooltip. Example: pTooltips.add((new TranslatableComponent("potion.whenDrank")).withStyle(ChatFormatting.DARK_PURPLE));

how do i have different behaviour for specific players?​

Each minecraft account has a Universally Unique Identifier. There are websites to get these from a player's username (like https://mcuuid.net). Have a list of people's uuids (ie. List<UUID> coolPeople = List.of(new UUID[]{UUID.fromString("bcb2252d-70de-4abc-9932-bc46bd5dc62f")});) and then have an if statement that checks coolPeople.contains(player.getUUID()). You could even put that list on pastebin or equivilent and fetch it with an http request so you could update it without changing your mod's code.

how to make an http request​

its just part of the normal jdk libraries

public static String get(String url) {
    try {
        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        InputStream responseStream = connection.getInputStream();

        return new BufferedReader(
                new InputStreamReader(responseStream, StandardCharsets.UTF_8))
                .lines()
                .collect(Collectors.joining("\n"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

how to change the enchantment glint colour​

its not easy. here's an overview of i did for 1.18.2,

I was hoping this would be defined as a hex value in the code but it's actually a texture: minecraft:textures/misc/enchanted_item_glint.png. This texture is at ItemRenderer.ENCHANT_GLINT_LOCATION but that variable is not actually referenced at render time so changing it back and forth wouldnt work. Instead, the texture is used as a RenderStateShard.TextureStateShard to create a RenderType. (the specific one i care about changing in this case is ARMOR_ENTITY_GLINT). I use a mixin to HumanoidArmorLayer that runs before and after renderArmorPiece is called. This allows me to access the actual item stack and then react to it in another mixin to a method that wouldn't have that context available. Then I mixin to ItemRenderer#getArmorFoilBuffer to change the render type that is used to create the vertex consumer to be rendered.

here's the code, dont forget the mixins and access transformers, https://github.com/LukeGrahamLandry/herobrine-thing/blob/main/src/main/java/ca/lukegrahamlandry/herobrinething/client/WhiteArmorGlintHelper.java

how to play a gif as an overlay in game​

https://gist.github.com/gigaherz/56b259126f715807c8e6c3dc055b924b

how to add a villager like trade gui to a custom entity​

have your entity implement Merchant

  • on mobInteract call setTradingPlayer and openTradingScreen
  • override getOffers , you'll have to make a MerchantOffers object (if you choose the trades randomly you'll probably want to save them in the entity's nbt so they stay the same for the same entity instance). look at WanderingTrader#updateTrades for an example of how to populate the trades. the individual trade options will be an object implementing ItemListing, there are a bunch of classes you can use in VillagerTrades, just scroll down a bit
  • you could just extend AbstractVillager and override updateTrades to save some time implementing the other Merchant stuff. depends if your entity needs to extend something else for some specific reason
  • if you actually want to load trades from a data pack instead of hardcoding them thats some extra work. you have to register a SimpleJsonResourceReloadListener on AddReloadListenerEvent, here's an example https://github.com/LukeGrahamLandry/modular-professions-mod/blob/forge-1.18/src/main/java/ca/lukegrahamlandry/modularprofessions/api/ProfessionDataLoader.java. you'd load the trade data in from json files and then use that to create the MerchantOffers described above

how do tile entity renderers work​

basically you end up with a render method that gets called every frame for each instance of your tile entity where you can run whatever rendering code you like. you're never going to find a detailed tutorial on what to actually do in that method cause there's like infinite variations and nobody likes dealing with rendering code. you pretty much just have to look around vanilla and other mod's code and slowly figure out what you can do

More Info: https://forge.gemwire.uk/wiki/Block_Entity_Renderer

how to create a moving entity​

start by registering your entity and renderer like in my projectiles tutorial but have it extend PathfinderMob then you can override registerGoals, look at some vanilla mobs for examples, like Cow uses WaterAvoidingRandomStrollGoal

if you want details on how goals work take a look at https://github.com/Tslat/SmartBrainLib/wiki/How-do-Goal-Selectors-Work