diff --git a/prismarine-viewer/viewer/lib/entities.ts b/prismarine-viewer/viewer/lib/entities.ts
index 48efb577..2a0ddeee 100644
--- a/prismarine-viewer/viewer/lib/entities.ts
+++ b/prismarine-viewer/viewer/lib/entities.ts
@@ -225,6 +225,7 @@ export class Entities extends EventEmitter {
     size?: number;
   } | {
     resolvedModel: BlockModel
+    modelName: string
   })
 
   constructor (public viewer: Viewer) {
@@ -426,7 +427,7 @@ export class Entities extends EventEmitter {
   getItemMesh (item, isDropped = false) {
     const textureUv = this.getItemUv?.(item)
     if (textureUv && 'resolvedModel' in textureUv) {
-      const mesh = getBlockMeshFromModel(this.viewer.world.material, textureUv.resolvedModel, item.name ?? item.itemId)
+      const mesh = getBlockMeshFromModel(this.viewer.world.material, textureUv.resolvedModel, textureUv.modelName)
       if (isDropped) {
         const SCALE = 0.5
         mesh.scale.set(SCALE, SCALE, SCALE)
diff --git a/prismarine-viewer/viewer/lib/holdingBlock.ts b/prismarine-viewer/viewer/lib/holdingBlock.ts
index 42581e81..641a2813 100644
--- a/prismarine-viewer/viewer/lib/holdingBlock.ts
+++ b/prismarine-viewer/viewer/lib/holdingBlock.ts
@@ -249,7 +249,7 @@ export default class HoldingBlock {
     this.objectOuterGroup.scale.set(scale, scale, scale)
   }
 
-  async initHandObject (material: THREE.Material, blockstatesModels: any, blocksAtlases: any, handItem?: HandItemBlock) {
+  async initHandObject (handItem?: HandItemBlock) {
     let animatingCurrent = false
     if (!this.swingAnimation && !this.blockSwapAnimation && this.isDifferentItem(handItem)) {
       animatingCurrent = true
@@ -414,7 +414,7 @@ export default class HoldingBlock {
 }
 
 export const getBlockMeshFromModel = (material: THREE.Material, model: BlockModel, name: string) => {
-  const blockProvider = worldBlockProvider(viewer.world.blockstatesModels, viewer.world.blocksAtlases, 'latest')
+  const blockProvider = worldBlockProvider(viewer.world.blockstatesModels, viewer.world.blocksAtlasParser!.atlas, 'latest')
   const worldRenderModel = blockProvider.transformModel(model, {
     name,
     properties: {}
diff --git a/prismarine-viewer/viewer/lib/worldrendererCommon.ts b/prismarine-viewer/viewer/lib/worldrendererCommon.ts
index 59d22dd9..327298af 100644
--- a/prismarine-viewer/viewer/lib/worldrendererCommon.ts
+++ b/prismarine-viewer/viewer/lib/worldrendererCommon.ts
@@ -117,8 +117,10 @@ export abstract class WorldRendererCommon<WorkerSend = any, WorkerReceive = any>
   itemsAtlasParser: AtlasParser | undefined
   blocksAtlasParser: AtlasParser | undefined
 
-  blocksAtlases = blocksAtlases
-  itemsAtlases = itemsAtlases
+  sourceData = {
+    blocksAtlases,
+    itemsAtlases
+  }
   customTextures: {
     items?: CustomTexturesData
     blocks?: CustomTexturesData
@@ -320,8 +322,8 @@ export abstract class WorldRendererCommon<WorkerSend = any, WorkerReceive = any>
   }
 
   async updateTexturesData (resourcePackUpdate = false, prioritizeBlockTextures?: string[]) {
-    const blocksAssetsParser = new AtlasParser(this.blocksAtlases, blocksAtlasLatest, blocksAtlasLegacy)
-    const itemsAssetsParser = new AtlasParser(this.itemsAtlases, itemsAtlasLatest, itemsAtlasLegacy)
+    const blocksAssetsParser = new AtlasParser(this.sourceData.blocksAtlases, blocksAtlasLatest, blocksAtlasLegacy)
+    const itemsAssetsParser = new AtlasParser(this.sourceData.itemsAtlases, itemsAtlasLatest, itemsAtlasLegacy)
 
     const blockTexturesChanges = {} as Record<string, string>
     const date = new Date()
diff --git a/prismarine-viewer/viewer/lib/worldrendererThree.ts b/prismarine-viewer/viewer/lib/worldrendererThree.ts
index 1845c98c..cab84b7b 100644
--- a/prismarine-viewer/viewer/lib/worldrendererThree.ts
+++ b/prismarine-viewer/viewer/lib/worldrendererThree.ts
@@ -67,7 +67,7 @@ export class WorldRendererThree extends WorldRendererCommon {
       holdingBlock.toBeRenderedItem = item
       return
     }
-    void holdingBlock.initHandObject(this.material, this.blockstatesModels, this.blocksAtlases, item)
+    void holdingBlock.initHandObject(item)
   }
 
   changeHandSwingingState (isAnimationPlaying: boolean, isLeft = false) {
diff --git a/src/index.ts b/src/index.ts
index 2fc886d5..77db040e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -181,6 +181,7 @@ viewer.entities.getItemUv = (item) => {
     if (renderInfo.blockData) {
       return {
         resolvedModel: renderInfo.blockData.resolvedModel,
+        modelName: renderInfo.modelName!
       }
     }
     if (renderInfo.slice) {
diff --git a/src/inventoryWindows.ts b/src/inventoryWindows.ts
index bfe96739..931348b5 100644
--- a/src/inventoryWindows.ts
+++ b/src/inventoryWindows.ts
@@ -179,6 +179,7 @@ export const renderSlot = (slot: GeneralInputItem, debugIsQuickbar = false): {
   blockData?: Record<string, { slice, path }> & { resolvedModel: BlockModel },
   scale?: number,
   slice?: number[],
+  modelName?: string
 } | undefined => {
   let itemModelName = slot.name
   const originalItemName = itemModelName
@@ -212,7 +213,8 @@ export const renderSlot = (slot: GeneralInputItem, debugIsQuickbar = false): {
     // is block
     return {
       texture: 'blocks',
-      blockData: itemTexture
+      blockData: itemTexture,
+      modelName: itemModelName
     }
   }
 }
diff --git a/src/resourcePack.ts b/src/resourcePack.ts
index 06bc2ce6..faea8ff7 100644
--- a/src/resourcePack.ts
+++ b/src/resourcePack.ts
@@ -460,11 +460,11 @@ const updateAllReplacableTextures = async () => {
 const repeatArr = (arr, i) => Array.from({ length: i }, () => arr)
 
 const updateTextures = async () => {
-  const blocksFiles = Object.keys(viewer.world.blocksAtlases.latest.textures)
-  const itemsFiles = Object.keys(viewer.world.itemsAtlases.latest.textures)
+  const origBlocksFiles = Object.keys(viewer.world.sourceData.blocksAtlases.latest.textures)
+  const origItemsFiles = Object.keys(viewer.world.sourceData.itemsAtlases.latest.textures)
   const { usedTextures: extraBlockTextures = new Set<string>() } = await prepareBlockstatesAndModels() ?? {}
-  const blocksData = await getResourcepackTiles('blocks', [...blocksFiles, ...extraBlockTextures])
-  const itemsData = await getResourcepackTiles('items', itemsFiles)
+  const blocksData = await getResourcepackTiles('blocks', [...origBlocksFiles, ...extraBlockTextures])
+  const itemsData = await getResourcepackTiles('items', origItemsFiles)
   await updateAllReplacableTextures()
   viewer.world.customTextures = {}
   if (blocksData) {
diff --git a/src/resourcePackItemDefinitions.ts b/src/resourcePackItemDefinitions.ts
new file mode 100644
index 00000000..9ec0b430
--- /dev/null
+++ b/src/resourcePackItemDefinitions.ts
@@ -0,0 +1,48 @@
+import fs from 'fs'
+
+export type ResourcePackItemDefinition = {
+  model: {
+    type: 'minecraft:model'
+    model: string
+    tints?: Array<{
+      type: 'minecraft:constant'
+      value: number // eg 12596533
+    }>
+  } | {
+    type: 'minecraft:empty'
+  }
+}
+
+export type ItemDefinitions = Record<string, ResourcePackItemDefinition>
+
+export type ItemRenderDefinitionInput = {
+  item: string
+}
+
+const readFilesSafe = async (path: string) => {
+  try {
+    return await fs.promises.readdir(path)
+  } catch (error) {
+    return null
+  }
+}
+
+export const readResourcePackItemDefinitions = async (assetsPath: string) => {
+  const namespaces = fs.readdirSync(assetsPath)
+
+  const itemDefinitions: ItemDefinitions = {}
+  for (const namespace of namespaces) {
+    // eslint-disable-next-line no-await-in-loop
+    const items = await readFilesSafe(`${assetsPath}/${namespace}/items`)
+    if (!items) continue
+    for (const item of items) {
+      if (!item.endsWith('.json')) continue
+      const file = fs.readFileSync(`${assetsPath}/${namespace}/items/${item}`, 'utf8')
+      const json = JSON.parse(file)
+      itemDefinitions[`${namespace}:${item}`] = json
+    }
+  }
+  return itemDefinitions
+}
+
+export const itemsDefaultNamespace = 'minecraft'