notebooks/Build_Assets_With_Python_2.ipynb

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    "## **Preface**\n",
    "This guide aims to extend the previous guide to learn more in depth about building assets.\n",
    "\n",
    "## **Prerequisites**\n",
    "Python examples in this guide requires only having `usd-core` library.\n",
    "\n",
    "### **Install the `usd-core` Python package**\n",
    "\n",
    "Install the [`usd-core`](https://pypi.org/project/usd-core/) Python package providing the core USD libraries. Note that it does not provide any of the optional plugins or imaging features from the complete USD distribution."
   ]
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    "! pip install usd-core\n",
    "\n",
    "# See https://pypi.org/project/usd-core/#history for a list of supported USD\n",
    "# versions."
   ]
  },
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    "## **Better Asset Structure**\n",
    "\n",
    "Let's examine an existent solution for creating USD assets.\n",
    "\n",
    "[Houdini Component Builder](https://www.sidefx.com/docs/houdini/solaris/component_builder.html) is a tool developed by sidefx that automates or enforces various best practices (this is especially useful for artists and studios new to USD).\n",
    "\n",
    "Acknowledgement, Many thank you to [USD and LOPs for Houdini Artists | FXPHD](https://www.fxphd.com/details/642/) for the amazing tips about better asset structures.\n",
    "\n",
    "\n",
    "> I'll modify the layer structure generated by component builder a little bit.\n",
    ">\n",
    "> For sake of simplicity, I'll use the default purpose. but, I'll include code for creating prims with proxy and render purposes."
   ]
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    "### **Geo Layer**\n",
    "Layer Structure: \n",
    "```\n",
    "geo.usda\n",
    "  ├── mata data\n",
    "  |     └── default prim: {asset-name}\n",
    "  ├── over ASSET_{variant-set-name}_variant_{variant-name}\n",
    "  |          ├── mata data\n",
    "  |          |     ├── {variant-set-name}\n",
    "  |          |     └──  hidden = true\n",
    "  |          └── xForm 'ASSET'\n",
    "  |                └── {variant-set-name}\n",
    "  |                        └── {variant-name}\n",
    "  |                               ├── meta data\n",
    "  |                               |    └── Kind: component \n",
    "  |                               └── Scope Geo\n",
    "  |                                    ├── extentsHint\n",
    "  |                                    ├── Scope proxy\n",
    "  |                                    |     ├── purpose proxy\n",
    "  |                                    |     └── geo prim\n",
    "  |                                    └── Scope render\n",
    "  |                                          ├── rel: proxy-prim\n",
    "  |                                          ├── purpose render\n",
    "  |                                          └── geo prim\n",
    "  └── def {asset-name}\n",
    "           └── mata data\n",
    "                   └── references\n",
    "                         └── variant_{variant-set-name}_{variant-name}/ASSET\n",
    "```\n",
    "Adding new variants is done through repeating the same process for `ASSET_{variant-set-name}_variant_{variant-name}`"
   ]
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      "#usda 1.0\n",
      "(\n",
      "    defaultPrim = \"My_Model\"\n",
      ")\n",
      "\n",
      "def \"My_Model\" (\n",
      "    prepend references = [\n",
      "        </ASSET_model_variant_normal/ASSET>,\n",
      "        </ASSET_model_variant_short/ASSET>,\n",
      "        </ASSET_model_variant_tall/ASSET>\n",
      "    ]\n",
      ")\n",
      "{\n",
      "}\n",
      "\n",
      "over \"ASSET_model_variant_normal\" (\n",
      "    hidden = true\n",
      ")\n",
      "{\n",
      "    def Xform \"ASSET\" (\n",
      "        variants = {\n",
      "            string model = \"normal\"\n",
      "        }\n",
      "        prepend variantSets = \"model\"\n",
      "    )\n",
      "    {\n",
      "        variantSet \"model\" = {\n",
      "            \"normal\" (\n",
      "                kind = \"component\"\n",
      "            ) {\n",
      "                custom float3[] extentsHint = [(-1, -1, -1), (1, 1, 1)]\n",
      "\n",
      "                def Scope \"Geo\"\n",
      "                {\n",
      "                    def Cube \"Cube\"\n",
      "                    {\n",
      "                        custom float3 xformOp:scale = (1, 1, 1)\n",
      "                        uniform token[] xformOpOrder = [\"xformOp:scale\"]\n",
      "                    }\n",
      "                }\n",
      "\n",
      "            }\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "over \"ASSET_model_variant_short\" (\n",
      "    hidden = true\n",
      ")\n",
      "{\n",
      "    def Xform \"ASSET\" (\n",
      "        variants = {\n",
      "            string model = \"short\"\n",
      "        }\n",
      "        prepend variantSets = \"model\"\n",
      "    )\n",
      "    {\n",
      "        variantSet \"model\" = {\n",
      "            \"short\" (\n",
      "                kind = \"component\"\n",
      "            ) {\n",
      "                custom float3[] extentsHint = [(-1, -0.5, -1), (1, 0.5, 1)]\n",
      "\n",
      "                def Scope \"Geo\"\n",
      "                {\n",
      "                    def Cube \"Cube\"\n",
      "                    {\n",
      "                        custom float3 xformOp:scale = (1, 0.5, 1)\n",
      "                        uniform token[] xformOpOrder = [\"xformOp:scale\"]\n",
      "                    }\n",
      "                }\n",
      "\n",
      "            }\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "over \"ASSET_model_variant_tall\" (\n",
      "    hidden = true\n",
      ")\n",
      "{\n",
      "    def Xform \"ASSET\" (\n",
      "        variants = {\n",
      "            string model = \"tall\"\n",
      "        }\n",
      "        prepend variantSets = \"model\"\n",
      "    )\n",
      "    {\n",
      "        variantSet \"model\" = {\n",
      "            \"tall\" (\n",
      "                kind = \"component\"\n",
      "            ) {\n",
      "                custom float3[] extentsHint = [(-1, -2, -1), (1, 2, 1)]\n",
      "\n",
      "                def Scope \"Geo\"\n",
      "                {\n",
      "                    def Cube \"Cube\"\n",
      "                    {\n",
      "                        custom float3 xformOp:scale = (1, 2, 1)\n",
      "                        uniform token[] xformOpOrder = [\"xformOp:scale\"]\n",
      "                    }\n",
      "                }\n",
      "\n",
      "            }\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "\n"
     ]
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   "source": [
    "# create Geo Layer\n",
    "from pxr import Usd, Sdf, UsdGeom, Kind\n",
    "\n",
    "variantSets = {\n",
    "    'model' : {\n",
    "                \n",
    "        'normal' : {'xformOp:scale' : (1, 1, 1),\n",
    "                    'extentsHint'   : [(-1, -1, -1), (1, 1, 1)]},\n",
    "    \n",
    "        'short'  : {'xformOp:scale' : (1, 0.5, 1),\n",
    "                    'extentsHint'   : [(-1, -0.5, -1), (1, 0.5, 1)]},\n",
    "       \n",
    "        'tall'   : {'xformOp:scale' : (1, 2, 1),\n",
    "                    'extentsHint'   : [(-1, -2, -1), (1, 2, 1)]}\n",
    "    }\n",
    "}\n",
    "\n",
    "\n",
    "attr_types = {\n",
    "   'extentsHint' :  Sdf.ValueTypeNames.Float3Array,\n",
    "    'xformOp:scale' : Sdf.ValueTypeNames.Float3\n",
    "}\n",
    "\n",
    "\n",
    "stage = Usd.Stage.CreateInMemory()\n",
    "\n",
    "my_model = stage.DefinePrim('/My_Model')\n",
    "stage.SetDefaultPrim(my_model.GetPrim())\n",
    "\n",
    "for variantSetName, variantSet in variantSets.items():\n",
    "    for variantName, variantData in variantSet.items():\n",
    "\n",
    "        variant = stage.OverridePrim('/ASSET_{}_variant_{}'.format(variantSetName, variantName))\n",
    "        variant .SetHidden(1)\n",
    "        \n",
    "        asset = UsdGeom.Xform.Define(stage, variant.GetPath().AppendPath('ASSET'))\n",
    "        \n",
    "        model_variant_set = asset.GetPrim().GetVariantSets().AddVariantSet(variantSetName)\n",
    "        model_variant_set.AddVariant(variantName)\n",
    "        model_variant_set.SetVariantSelection(variantName)\n",
    "        with model_variant_set.GetVariantEditContext():\n",
    "            Usd.ModelAPI(asset).SetKind(Kind.Tokens.component)\n",
    "            geoPrim = UsdGeom.Scope.Define(stage, asset.GetPath().AppendPath('Geo'))\n",
    "            cube_model = UsdGeom.Cube.Define(stage, geoPrim.GetPath().AppendPath('Cube'))\n",
    "            \n",
    "            attrName = 'xformOp:scale'\n",
    "            cube_model.GetPrim().CreateAttribute(attrName, attr_types[attrName]).Set(variantData[attrName])\n",
    "            cube_model.GetPrim().CreateAttribute('xformOpOrder', Sdf.ValueTypeNames.Token).Set([attrName])\n",
    "            attrName = 'extentsHint'\n",
    "            asset.GetPrim().CreateAttribute(attrName, attr_types[attrName]).Set(variantData[attrName])  # Add extents hint to asset\n",
    "            \n",
    "            # proxy_model = UsdGeom.Scope.Define(stage, geoPrim.GetPath().AppendPath('Proxy'))\n",
    "            # proxy_model.GetPrim().CreateAttribute('purpose', Sdf.ValueTypeNames.Token).Set('proxy')\n",
    "            # proxy_cube_model = UsdGeom.Cube.Define(stage, proxy_model.GetPath().AppendPath('Cube'))\n",
    "            \n",
    "            # render_model = UsdGeom.Scope.Define(stage, geoPrim.GetPath().AppendPath('Render'))\n",
    "            # render_model.GetPrim().CreateAttribute('purpose', Sdf.ValueTypeNames.Token).Set('render')\n",
    "            # render_model.GetPrim().CreateRelationship('proxyPrim').SetTargets([proxy_model.GetPath()])\n",
    "            # render_cube_model = UsdGeom.Cube.Define(stage, render_model.GetPath().AppendPath('Cube'))\n",
    "\n",
    "        variant.SetSpecifier(Sdf.SpecifierOver)  # force prim to be over.\n",
    "        my_model.GetReferences().AddInternalReference(asset.GetPath())\n",
    "\n",
    "print(stage.GetRootLayer().ExportToString())\n",
    "stage.GetRootLayer().Export('examples/build_assets_with_python_2/better_asset_structure/geo.usda')"
   ]
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    "## **Mtl Layer**\n",
    "Layer structure 1: Material libarary contains all materials (e.g. Red, Green and Blue) + variant bindings (Red material binding, ...)\n",
    "\n",
    "```\n",
    "mtl.usda\n",
    "  ├── mata data\n",
    "  |     └── default prim: {asset-name}\n",
    "  ├── over ASSET-Material-Library\n",
    "  |          └── Scope Mtl\n",
    "  |               └── Material 'variant-material-name'\n",
    "  |                     ├── output:surface\n",
    "  |                     └── Shader 'variant-material-name'\n",
    "  |                           └── {variant-name}\n",
    "  └──  def {asset-name}\n",
    "               ├── mata data\n",
    "               |     ├── references\n",
    "               |     |      └── ASSET-Material-Library\n",
    "               |     └── {variant-set-name}\n",
    "               ├── Scope Mtl (empty prim)\n",
    "               └── {variant-set-name}\n",
    "                      └── {variant-material-name}\n",
    "                            └── over Geo\n",
    "                               ├── over proxy\n",
    "                               |     ├── apiSchemas \"MaterialBindingAPI\"\n",
    "                               |     └── rel material:binding  {variant-material-name}_Preview \n",
    "                               └── over render\n",
    "                                     ├── apiSchemas \"MaterialBindingAPI\"\n",
    "                                     └── rel material:binding  {variant-material-name}\n",
    "```\n",
    "\n",
    "Layer structure 2: Variant Material and bindings (e.g. Red Material with its binding, ...) \n",
    "In short: `def material + over geo(binding)`\n",
    "```\n",
    "mtl.usda\n",
    "  ├── mata data\n",
    "  |     └── default prim: {asset-name}\n",
    "  ├── over ASSET_{variant-set-name}_variant_{material-name}\n",
    "  |          ├── mata data\n",
    "  |          |      └──  hidden = true\n",
    "  |          └── xForm 'ASSET'\n",
    "  |                  ├── mata data\n",
    "  |                  |      └── {variant-set-name}\n",
    "  |                  ├── Scope Mtl\n",
    "  |                  |      └── Material 'variant-material-name'\n",
    "  |                  |            ├── output:surface\n",
    "  |                  |            └── Shader 'variant-material-name'\n",
    "  |                  |                   └── {variant-name}\n",
    "  |                  └── {variant-set-name}\n",
    "  |                         └── {variant-name}\n",
    "  |                                └── over Geo\n",
    "  |                                   ├── over proxy\n",
    "  |                                   |     ├── apiSchemas \"MaterialBindingAPI\"\n",
    "  |                                   |     └── rel material:binding  {variant-material-name}_Preview \n",
    "  |                                   └── over render\n",
    "  |                                         ├── apiSchemas \"MaterialBindingAPI\"\n",
    "  |                                         └── rel material:binding  {variant-material-name}\n",
    "  └──  def {asset-name}\n",
    "             └── mata data\n",
    "                  └── references\n",
    "                          └── ASSET_{variant-set-name}_variant_{material-name}\n",
    "```\n",
    "Adding new variants is done through repeating the same process for `ASSET_{variant-set-name}_variant_{material-name}`\n",
    "\n",
    "> I'll use `Layer structure 2` for consistency.\n",
    "> Also, to avoid loading unused materials."
   ]
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     "text": [
      "#usda 1.0\n",
      "(\n",
      "    defaultPrim = \"My_Model\"\n",
      ")\n",
      "\n",
      "def \"My_Model\" (\n",
      "    prepend references = [\n",
      "        </ASSET_material_variant_red/ASSET>,\n",
      "        </ASSET_material_variant_green/ASSET>,\n",
      "        </ASSET_material_variant_blue/ASSET>\n",
      "    ]\n",
      ")\n",
      "{\n",
      "}\n",
      "\n",
      "over \"ASSET_material_variant_red\" (\n",
      "    hidden = true\n",
      ")\n",
      "{\n",
      "    def Xform \"ASSET\" (\n",
      "        variants = {\n",
      "            string material = \"red\"\n",
      "        }\n",
      "        prepend variantSets = \"material\"\n",
      "    )\n",
      "    {\n",
      "        variantSet \"material\" = {\n",
      "            \"red\" {\n",
      "                def Scope \"Mtl\"\n",
      "                {\n",
      "                    def Material \"red\"\n",
      "                    {\n",
      "                        token outputs:surface.connect = </ASSET_material_variant_red/ASSET/Mtl/red/redShader.outputs:surface>\n",
      "\n",
      "                        def Shader \"redShader\"\n",
      "                        {\n",
      "                            uniform token info:id = \"UsdPreviewSurface\"\n",
      "                            color3f inputs:diffuseColor = (1, 0, 0)\n",
      "                            token outputs:surface\n",
      "                        }\n",
      "                    }\n",
      "                }\n",
      "\n",
      "                over \"Geo\"\n",
      "                {\n",
      "                    over \"Cube\" (\n",
      "                        prepend apiSchemas = [\"MaterialBindingAPI\"]\n",
      "                    )\n",
      "                    {\n",
      "                        rel material:binding = </ASSET_material_variant_red/ASSET/Mtl/red>\n",
      "                    }\n",
      "                }\n",
      "\n",
      "            }\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "over \"ASSET_material_variant_green\" (\n",
      "    hidden = true\n",
      ")\n",
      "{\n",
      "    def Xform \"ASSET\" (\n",
      "        variants = {\n",
      "            string material = \"green\"\n",
      "        }\n",
      "        prepend variantSets = \"material\"\n",
      "    )\n",
      "    {\n",
      "        variantSet \"material\" = {\n",
      "            \"green\" {\n",
      "                def Scope \"Mtl\"\n",
      "                {\n",
      "                    def Material \"green\"\n",
      "                    {\n",
      "                        token outputs:surface.connect = </ASSET_material_variant_green/ASSET/Mtl/green/greenShader.outputs:surface>\n",
      "\n",
      "                        def Shader \"greenShader\"\n",
      "                        {\n",
      "                            uniform token info:id = \"UsdPreviewSurface\"\n",
      "                            color3f inputs:diffuseColor = (0, 1, 0)\n",
      "                            token outputs:surface\n",
      "                        }\n",
      "                    }\n",
      "                }\n",
      "\n",
      "                over \"Geo\"\n",
      "                {\n",
      "                    over \"Cube\" (\n",
      "                        prepend apiSchemas = [\"MaterialBindingAPI\"]\n",
      "                    )\n",
      "                    {\n",
      "                        rel material:binding = </ASSET_material_variant_green/ASSET/Mtl/green>\n",
      "                    }\n",
      "                }\n",
      "\n",
      "            }\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "over \"ASSET_material_variant_blue\" (\n",
      "    hidden = true\n",
      ")\n",
      "{\n",
      "    def Xform \"ASSET\" (\n",
      "        variants = {\n",
      "            string material = \"blue\"\n",
      "        }\n",
      "        prepend variantSets = \"material\"\n",
      "    )\n",
      "    {\n",
      "        variantSet \"material\" = {\n",
      "            \"blue\" {\n",
      "                def Scope \"Mtl\"\n",
      "                {\n",
      "                    def Material \"blue\"\n",
      "                    {\n",
      "                        token outputs:surface.connect = </ASSET_material_variant_blue/ASSET/Mtl/blue/blueShader.outputs:surface>\n",
      "\n",
      "                        def Shader \"blueShader\"\n",
      "                        {\n",
      "                            uniform token info:id = \"UsdPreviewSurface\"\n",
      "                            color3f inputs:diffuseColor = (0, 0, 1)\n",
      "                            token outputs:surface\n",
      "                        }\n",
      "                    }\n",
      "                }\n",
      "\n",
      "                over \"Geo\"\n",
      "                {\n",
      "                    over \"Cube\" (\n",
      "                        prepend apiSchemas = [\"MaterialBindingAPI\"]\n",
      "                    )\n",
      "                    {\n",
      "                        rel material:binding = </ASSET_material_variant_blue/ASSET/Mtl/blue>\n",
      "                    }\n",
      "                }\n",
      "\n",
      "            }\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "\n"
     ]
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   "source": [
    "# Create Material Layer\n",
    "# Material X won't be used in this example as it's not available inside usd-core.\n",
    "from pxr import Usd, Sdf, UsdGeom, UsdShade, Kind\n",
    "\n",
    "variantSets = {\n",
    "    'material' : {\n",
    "        'red'   : {'diffuseColor' : (1, 0, 0)},\n",
    "        'green' : {'diffuseColor' : (0, 1, 0)},\n",
    "        'blue'  : {'diffuseColor' : (0, 0, 1)},      \n",
    "    }\n",
    "}\n",
    "\n",
    "stage = Usd.Stage.CreateInMemory()\n",
    "\n",
    "my_model = stage.DefinePrim('/My_Model')\n",
    "stage.SetDefaultPrim(my_model.GetPrim())\n",
    "\n",
    "for variantSetName, variantSet in variantSets.items():\n",
    "    for variantName, variantData in variantSet.items():\n",
    "        variant = stage.OverridePrim('/ASSET_{}_variant_{}'.format(variantSetName, variantName))\n",
    "        variant .SetHidden(1)\n",
    "        \n",
    "        asset = UsdGeom.Xform.Define(stage, variant.GetPath().AppendPath('ASSET'))\n",
    "        \n",
    "        materialVariantSet = asset.GetPrim().GetVariantSets().AddVariantSet(variantSetName)\n",
    "        materialVariantSet.AddVariant(variantName)\n",
    "        materialVariantSet.SetVariantSelection(variantName)\n",
    "        with materialVariantSet.GetVariantEditContext():\n",
    "        \n",
    "            materialScope = UsdGeom.Scope.Define(stage, asset.GetPath().AppendPath('Mtl'))\n",
    "            \n",
    "            materialVariant = UsdShade.Material.Define(stage, materialScope.GetPath().AppendPath(variantName))\n",
    "            shaderPreview = UsdShade.Shader.Define(stage, materialVariant.GetPath().AppendPath('{}Shader'.format(variantName)))\n",
    "            materialVariant.CreateSurfaceOutput().ConnectToSource(shaderPreview.ConnectableAPI(), \"surface\")\n",
    "            shaderPreview.CreateIdAttr('UsdPreviewSurface')\n",
    "            shaderPreview.CreateInput('diffuseColor', Sdf.ValueTypeNames.Color3f).Set(variantData['diffuseColor'])\n",
    "\n",
    "            cubePrim = stage.OverridePrim(asset.GetPath().AppendPath('Geo/Cube'))  # Same prim name as in geo.usda\n",
    "            \n",
    "            cubePrim.GetPrim().ApplyAPI(\"MaterialBindingAPI\")\n",
    "            UsdShade.MaterialBindingAPI(cubePrim.GetPrim()).Bind(materialVariant)  # add material binding to geo override\n",
    "        \n",
    "        variant.SetSpecifier(Sdf.SpecifierOver)  # force prim to be over.\n",
    "        my_model.GetReferences().AddInternalReference(asset.GetPath())\n",
    "\n",
    "print(stage.GetRootLayer().ExportToString())\n",
    "stage.GetRootLayer().Export('examples/build_assets_with_python_2/better_asset_structure/mtl.usda')"
   ]
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   "source": [
    "## **Payload Layer**\n",
    "Layer Structure:\n",
    "```\n",
    "payload.usda\n",
    "  ├── mata data\n",
    "  |     └── default prim: {asset-name}\n",
    "  └──  def {asset-name}\n",
    "            └── meta data\n",
    "                 ├── Kind: component \n",
    "                 └── references\n",
    "                       ├── geo.usda\n",
    "                       └── mtl.usda\n",
    "```"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "id": "7fa6ce8c-774f-4332-bed7-e57c95ac3842",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "#usda 1.0\n",
      "(\n",
      "    defaultPrim = \"My_Model\"\n",
      ")\n",
      "\n",
      "def \"My_Model\" (\n",
      "    kind = \"component\"\n",
      "    prepend references = [\n",
      "        @./geo.usda@,\n",
      "        @./mtl.usda@\n",
      "    ]\n",
      ")\n",
      "{\n",
      "}\n",
      "\n",
      "\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Create Payload\n",
    "from pxr import Usd, Kind\n",
    "\n",
    "stage = Usd.Stage.CreateInMemory()\n",
    "\n",
    "my_model = stage.DefinePrim('/My_Model')\n",
    "stage.SetDefaultPrim(my_model.GetPrim())\n",
    "\n",
    "Usd.ModelAPI(my_model).SetKind(Kind.Tokens.component)\n",
    "\n",
    "my_model.GetPrim().GetReferences().AddReference('./geo.usda')  # hardcoded layer name\n",
    "my_model.GetPrim().GetReferences().AddReference('./mtl.usda')  # hardcoded layer name\n",
    "\n",
    "print(stage.GetRootLayer().ExportToString())\n",
    "stage.GetRootLayer().Export('examples/build_assets_with_python_2/better_asset_structure/payload.usda')"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5db9771a-9b1f-405b-a8a0-21067fbd677d",
   "metadata": {},
   "source": [
    "## **Asset Layer**\n",
    "Layer Structure:\n",
    "```\n",
    "my_asset.usda\n",
    "  ├── mata data\n",
    "  |     └── default prim: {asset-name}\n",
    "  ├──  def {asset-name}\n",
    "  |         ├── mata data\n",
    "  |         |     ├── asset info\n",
    "  |         |     |     ├── identifier (asset layer itself)\n",
    "  |         |     |     ├── thumbnail (a thumbnail for the asset this is added for feature parity with Houdini)\n",
    "  |         |     |     └── name\n",
    "  |         |     ├── inherits __class__/{asset-name}\n",
    "  |         |     ├── payload payload.usda\n",
    "  |         |     ├── Variant Sets : [{model-variant-set}, {material-variant-set}]\n",
    "  |         |     └── Kind: component\n",
    "  |         ├── {model-variant-set}\n",
    "  |         |     └── {variant-model-name} (empty variants, model variants should include extentHint property)\n",
    "  |         |          ├── meta data\n",
    "  |         |          |     ├── apiSchemas \"GeomModelAPI\"\n",
    "  |         |          |     └── Kind: component\n",
    "  |         |          └── extentsHint\n",
    "  |         └── {material-variant-set}\n",
    "  |               └── {variant-material-name} (empty variants)\n",
    "  └── class __class__\n",
    "          └── {asset-name}\n",
    "```"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "id": "3530d09f-1ce3-4523-90ba-d968fae9a103",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "#usda 1.0\n",
      "(\n",
      "    defaultPrim = \"My_Model\"\n",
      ")\n",
      "\n",
      "def Xform \"My_Model\" (\n",
      "    assetInfo = {\n",
      "        asset identifier = @./my_model.usda@\n",
      "        string name = \"My_Model\"\n",
      "        asset thumbnail = @thumbnail-path@\n",
      "    }\n",
      "    prepend inherits = </__class__/My_Model>\n",
      "    kind = \"component\"\n",
      "    prepend payload = @./payload.usda@</My_Model>\n",
      "    variants = {\n",
      "        string material = \"red\"\n",
      "        string model = \"normal\"\n",
      "    }\n",
      "    prepend variantSets = [\"model\", \"material\"]\n",
      ")\n",
      "{\n",
      "    variantSet \"model\" = {\n",
      "        \"normal\" (\n",
      "            prepend apiSchemas = [\"GeomModelAPI\"]\n",
      "            kind = \"component\"\n",
      "        ) {\n",
      "            custom float3[] extentsHint = [(-1, -1, -1), (1, 1, 1)]\n",
      "\n",
      "        }\n",
      "        \"short\" (\n",
      "            prepend apiSchemas = [\"GeomModelAPI\"]\n",
      "            kind = \"component\"\n",
      "        ) {\n",
      "            custom float3[] extentsHint = [(-1, -0.5, -1), (1, 0.5, 1)]\n",
      "\n",
      "        }\n",
      "        \"tall\" (\n",
      "            prepend apiSchemas = [\"GeomModelAPI\"]\n",
      "            kind = \"component\"\n",
      "        ) {\n",
      "            custom float3[] extentsHint = [(-1, -2, -1), (1, 2, 1)]\n",
      "\n",
      "        }\n",
      "    }\n",
      "    variantSet \"material\" = {\n",
      "        \"blue\" {\n",
      "\n",
      "        }\n",
      "        \"green\" {\n",
      "\n",
      "        }\n",
      "        \"red\" {\n",
      "\n",
      "        }\n",
      "    }\n",
      "}\n",
      "\n",
      "class \"__class__\"\n",
      "{\n",
      "    class \"My_Model\"\n",
      "    {\n",
      "    }\n",
      "}\n",
      "\n",
      "\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# Create Asset Layer\n",
    "from pxr import Usd, Sdf, UsdGeom, UsdShade\n",
    "\n",
    "variantSets = {\n",
    "    'model' : {\n",
    "        'tall'   : {'xformOp:scale' : (1, 2, 1),\n",
    "                    'extentsHint'   : [(-1, -2, -1), (1, 2, 1)] },\n",
    "        \n",
    "        'short'  : {'xformOp:scale' : (1, 0.5, 1),\n",
    "                    'extentsHint'   : [(-1, -0.5, -1), (1, 0.5, 1)]},\n",
    "        \n",
    "        'normal' : {'xformOp:scale' : (1, 1, 1),\n",
    "                    'extentsHint'   : [(-1, -1, -1), (1, 1, 1)]}        \n",
    "    },\n",
    "    'material' : {\n",
    "        'blue'  : {'diffuseColor' : (0, 0, 1)}, \n",
    "        'green' : {'diffuseColor' : (0, 1, 0)},\n",
    "        'red'   : {'diffuseColor' : (1, 0, 0)},             \n",
    "    }\n",
    "}\n",
    "\n",
    "attr_types = {\n",
    "   'extentsHint' :  Sdf.ValueTypeNames.Float3Array,\n",
    "    'xformOp:scale' : Sdf.ValueTypeNames.Float3\n",
    "}\n",
    "\n",
    "\n",
    "stage = Usd.Stage.CreateInMemory()\n",
    "\n",
    "my_model = stage.DefinePrim('/My_Model', 'Xform')\n",
    "stage.SetDefaultPrim(my_model.GetPrim())\n",
    "\n",
    "my_model_class = stage.CreateClassPrim('/__class__')\n",
    "my_model_class = stage.CreateClassPrim(my_model_class.GetPath().AppendPath('My_Model'))\n",
    "my_model.GetPrim().GetInherits().AddInherit(my_model_class.GetPath())\n",
    "\n",
    "my_model.SetAssetInfo( {'identifier' : Sdf.AssetPath('./my_model.usda') , 'name' : 'My_Model'})\n",
    "my_model.SetAssetInfoByKey('thumbnail', Sdf.AssetPath('thumbnail-path'))  # FYI, If I were inside houdini, I would actually save a view snap\n",
    "                                                                          # and save it as my thumbnail.\n",
    "                                                                          # https://www.sidefx.com/docs/houdini/commands/viewsnapshot.html           \n",
    "my_model.GetPrim().GetPayloads().AddPayload('./payload.usda', '/My_Model')\n",
    "\n",
    "Usd.ModelAPI(my_model).SetKind(Kind.Tokens.component)\n",
    "\n",
    "for variantSetName, variantSet in variantSets.items():\n",
    "    for variantName, variantData in variantSet.items():\n",
    "        \n",
    "        variantSet = my_model.GetPrim().GetVariantSets().AddVariantSet(variantSetName)\n",
    "        variantSet.AddVariant(variantName)\n",
    "        variantSet.SetVariantSelection(variantName)\n",
    "\n",
    "        if variantSetName == 'model':\n",
    "            with variantSet.GetVariantEditContext():\n",
    "                Usd.ModelAPI(my_model).SetKind(Kind.Tokens.component)\n",
    "                \n",
    "                my_model.GetPrim().ApplyAPI(\"GeomModelAPI\")\n",
    "                \n",
    "                attrName = 'extentsHint'\n",
    "                my_model.GetPrim().CreateAttribute(attrName, attr_types[attrName]).Set(variantData[attrName])  # Add extents hint to asset         \n",
    "    \n",
    "print(stage.GetRootLayer().ExportToString())\n",
    "stage.GetRootLayer().Export('examples/build_assets_with_python_2/better_asset_structure/my_model.usda')"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "acbdf986-dc61-41ff-9cf2-23627dfdd2da",
   "metadata": {},
   "source": [
    "**Result:** To be honset, it looks the same as our previous assets. But, This structure provides more capabilities!\n",
    "> Notice how `usdview` uses `extentsHint` property to draw the bounding box while pay is unloaded.\n",
    "\n",
    "> I had to click on the view port in `usdview` to show the updated boudning box value.\n",
    "\n",
    "![](../resources/build_assets_with_python_2/better_asset_structure.gif)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "d8739d16-0ea3-406e-8fb8-e99eb67d0bde",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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