Using PythonAPI to assign Normal and Opacity Maps onto a Material

Omniverse Synthetic Data Generation (SDG)
1

Hello,

I’ve been racking my brains recently trying to figure out how to to assign Normal and Opacity Maps onto a Material in USD Composer using the Python API. I’m also using the omni.replicator extension. Has anyone achieved this before?

Many thanks in advance

3

What version of USD Composer? That’s likely to be a pretty old version of replicator. If you’re willing to use an up to date version of Isaac Sim (what’s recommended for SDG with replicator), you can use a “Functional” python approach, and manipulate material attributes like so.

Note the texture assignment instead would have a path to a normal texture and opacity texture, and the value names would be inputs:normalmap_texture and ‘inputs:opacity_texture respectively.

import asyncio
import omni.usd
from pxr import Gf, Usd, UsdShade, Sdf
import omni.replicator.core as rep
import numpy as np
from omni.replicator.core import functional as F

# https://docs.omniverse.nvidia.com/dev-guide/latest/programmer_ref/usd/materials/create-mdl-material.html

def change_mat_color3(stage, mat_prim, attribute, value):
    shader_prim = mat_prim.GetChild("Shader")
    if not shader_prim.GetAttribute(attribute).IsValid():
        shader_prim.CreateAttribute(attribute, Sdf.ValueTypeNames.Color3f, custom=True).Set((0.0, 0.0, 0.0))

    # Set the diffuse color to the input color
    shader_prim.GetAttribute(attribute).Set(Gf.Vec3f([value[0], value[1], value[2]]))

def change_mat_texture(stage, mat_prim, attribute, texture_path):
    shader_prim = mat_prim.GetChild("Shader")
    if not shader_prim.GetAttribute(attribute).IsValid():
        shader_prim.CreateAttribute(attribute, Sdf.ValueTypeNames.Asset, custom=True).Set("")

    # Set the diffuse color to the input color
    shader_prim.GetAttribute(attribute).Set(texture_path)

def change_mat_float2(stage, mat_prim, attribute, value):
    shader_prim = mat_prim.GetChild("Shader")
    if not shader_prim.GetAttribute(attribute).IsValid():        
        shader_prim.CreateAttribute(attribute, Sdf.ValueTypeNames.Float2, custom=True).Set(Gf.Vec2f(0.0, 0.0))

    # Set the diffuse color to the input color
    shader_prim.GetAttribute(attribute).Set(Gf.Vec2f([value[0], value[1]]))

def change_mat_float(stage, mat_prim, attribute, value):
    shader_prim = mat_prim.GetChild("Shader")
    if not shader_prim.GetAttribute(attribute).IsValid():        
        shader_prim.CreateAttribute(attribute, Sdf.ValueTypeNames.Float, custom=True).Set(0.0)

    # Set the diffuse color to the input color
    shader_prim.GetAttribute(attribute).Set(value)


# Set default parameters
NUM_IMAGES = 10
DIFF_TEXTURE_PATH = "https://omniverse-content-production.s3.us-west-2.amazonaws.com/Materials/2023_1/vMaterials_2/Masonry/textures/clinker_diff.jpg"

# Get the current USD context, and make a new stage
ctx = omni.usd.get_context()
ctx.new_stage()
stage = omni.usd.get_context().get_stage()

# Set the scene UP axis and the default unit size
rep.settings.set_stage_up_axis("Z")
rep.settings.set_stage_meters_per_unit(1.0)

# Randomization Seed
rng = np.random.RandomState(1234)

# Set the renderer
rep.settings.set_render_pathtraced(samples_per_pixel=16)
#rep.settings.set_render_rtx_realtime()

# Use Replicator to make a new material from OmniPBR.mdl
rep_material = F.create.material(mdl="OmniPBR.mdl", diffuse_color_constant=(0,0,1))

# Create ground plane and a blue cube
ground = F.create.plane(scale=100, position=(0,0,0))
cube_01 = F.create.cube(position=(0,0,1.25), material=rep_material, scale=1, semantics={"class": "cube"}, rotation=(0,0,-40))

# Create a distant light
light = F.create_batch.distant_light(position=(0, 2, 0), color=(1, 0.8, 0.6), intensity=800, angle=1, rotation=(0,-40,-150))

# Create a camera
camera = F.create.camera(look_at=(0,0,1.25), position=(0, 5, 3), focal_length=16)

# Create a render product
rp = rep.create.render_product(camera, (1280, 704))

# Define the use of the default Basic Writer and initialize it
writer = rep.WriterRegistry.get("BasicWriter")
writer.initialize(output_dir="material_attributes", rgb=True)

# For using `writer.schedule_write()` it is critical that `trigger=None` is set in the writer
writer.attach(rp, trigger= None)

async def capture():

    for i in range(NUM_IMAGES):

        # Use custom function to change the attributes of the material
        change_mat_color3(stage, rep_material, "inputs:diffuse_tint", rng.uniform((0.0, 0.0, 0.0), (1.0, 1.0, 1.0)))
        change_mat_texture(stage, rep_material, "inputs:diffuse_texture", DIFF_TEXTURE_PATH)
        change_mat_float2(stage, rep_material, "inputs:texture_translate", rng.uniform((0.0, 0.0), (1.0, 1.0)))
        change_mat_float2(stage, rep_material, "inputs:texture_scale", rng.uniform((0.2, 0.2), (2.0, 2.0)))
        change_mat_float(stage, rep_material, "inputs:texture_rotate", rng.uniform(0.0, 360.0))

        await rep.orchestrator.step_async(wait_for_render=False)
        writer.schedule_write()

asyncio.ensure_future(capture())