Exercise: Variation Workstream#

In this exercise, we’ll simulate a surfacing artist working at the assembly level to make shading variation choices on multiple buildings in city_blockA. We’ve added a shading workstream to city_blockA, allowing a surfacing artist to work at the city block context and see how their variation choices on individual buildings look in context.

To simulate a surfacing artist working on city_blockA, you’ll create a script that makes random accentColor and exteriorType choices. These choices will be authored to the contents/shading.usd sublayer of the city_blockA asset.

  1. Run the following command in Visual Studio Code to open city_blockA in usdview:

Windows:

.\scripts\usdview.bat .\asset_structure\exercise_12\city_blockA.usd

Linux:

./scripts/usdview.sh ./asset_structure/exercise_12/city_blockA.usd

Note the starting state of city_blockA. All of the buildings have a stucco exterior and red awning.

  1. In Visual Studio Code, open the following file: asset_structure/exercise_12/set_bldg_variations.py

  2. Let’s complete our script for randomizing the building variations. Add the code below into the block:

1for prim in stage.Traverse():
2    if prim.IsComponent() and prim.GetVariantSets().HasVariantSet("exteriorType"):
3        accent_primvar = UsdGeom.PrimvarsAPI(prim).GetPrimvar("accentColor")
4        accent_primvar.Set(random.choice(accent_choices))
5        vset = prim.GetVariantSet("exteriorType")
6        vset.SetVariantSelection(random.choice(vset.GetVariantNames()))

In this snippet, we are traversing through the stage and setting a random variant choice and accent color for every component asset that has an exteriorType variant set.

  1. Save the file and then execute the script using the following command:

Windows:

python .\asset_structure\exercise_12\set_bldg_variations.py

Linux:

python ./asset_structure/exercise_12/set_bldg_variations.py

  1. The output will now be in contents/shading.usd. Let’s go ahead and view the updated asset in usdview by running the following command in Visual Studio Code:

Windows:

.\scripts\usdview.bat .\asset_structure\exercise_12\city_blockA.usd

Linux:

./scripts/usdview.sh ./asset_structure/exercise_12/city_blockA.usd

Your results may look different, but you should now see some variant in the building exterior and accent colors:

You can rerun the script and view the results again in usdview if you want to try to get a different randomized result.

  1. In Visual Studio Code, open the following file:
    asset_structure/exercise_12/contents/shading.usd

Note the sparse overrides that our script authored in this layer.