Blame for scripts/build_openarm.py

"""OpenArm bimanual USD from NVIDIA's Isaac Sim asset, with the links and joints of
openarm_bimanual_web.urdf, materials as UsdPreviewSurface and geometry decimated for the web."""

import json
import sys

import fast_simplification
import numpy as np
from pxr import Gf, Sdf, Usd, UsdGeom, UsdPhysics, UsdShade

import robotusd as ru

SOURCE, URDF, OUT = sys.argv[1:4]
KEEP = float(sys.argv[4]) if len(sys.argv) > 4 else 0.08  # share of triangles kept
SIDES = ("left", "right")

layer = ru.flatten(SOURCE, {"Sensor": "None"})
stage = Usd.Stage.Open(layer)
root = str(stage.GetDefaultPrim().GetPath())

# Omniverse render settings, colliders (not drawn, and most of the bytes) and the TCP bodies,
# which sit 13 mm from the URDF's hand_tcp.
ru.remove(layer, "/Render")
for path in [p.GetPath() for p in stage.Traverse() if p.GetName() == "collisions"]:
    ru.remove(layer, path)
for side in SIDES:
    ru.remove(layer, f"{root}/joints/openarm_{side}_ee_tcp_joint")
    ru.remove(layer, f"{root}/openarm_{side}_ee_tcp")

# link7 -> hand is fixed in the URDF; NVIDIA made it a revolute with a zero range.
for side in SIDES:
    path = f"{root}/joints/openarm_{side}_hand"
    spec = layer.GetPrimAtPath(path)
    spec.typeName = "PhysicsFixedJoint"
    for name in list(spec.attributes.keys()):
        if not name.startswith(("physics:body", "physics:localPos", "physics:localRot", "physics:jointEnabled", "physics:collisionEnabled", "physics:breakForce", "physics:breakTorque", "physics:excludeFromArticulation")):
            spec.RemoveProperty(spec.attributes[name])
    spec.SetInfo("apiSchemas", Sdf.TokenListOp())
    ru.rename(layer, path, f"{side}_openarm_hand_joint")

ru.rename(layer, f"{root}/openarm_body_link", "openarm_body_link0")

# The URDF's mimic finger moves over the same range as the finger it follows.
for side in SIDES:
    joint = UsdPhysics.PrismaticJoint(stage.GetPrimAtPath(f"{root}/joints/openarm_{side}_finger_joint2"))
    joint.GetLowerLimitAttr().Set(0.0)
    joint.GetUpperLimitAttr().Set(0.044)

# OmniPBR (MDL) only sets a diffuse color here: the same material as UsdPreviewSurface.
for path in [p.GetPath() for p in stage.Traverse() if p.IsA(UsdShade.Material)]:
    p = stage.GetPrimAtPath(path)
    material = UsdShade.Material(p)
    mdl = next(c for c in p.GetChildren() if c.IsA(UsdShade.Shader))
    shader = UsdShade.Shader(mdl)

    def value(name, default):
        i = shader.GetInput(name)
        return i.Get() if i and i.Get() is not None else default

    color = value("diffuse_color_constant", Gf.Vec3f(0.2, 0.2, 0.2))
    roughness = value("reflection_roughness_constant", 0.5)
    metallic = value("metallic_constant", 0.0)
    ru.remove(layer, mdl.GetPath())
    mspec = layer.GetPrimAtPath(p.GetPath())
    for name in list(mspec.attributes.keys()):
        if name.startswith("outputs:"):
            mspec.RemoveProperty(mspec.attributes[name])
    preview = UsdShade.Shader.Define(stage, p.GetPath().AppendChild("PreviewSurface"))
    preview.CreateIdAttr("UsdPreviewSurface")
    preview.CreateInput("diffuseColor", Sdf.ValueTypeNames.Color3f).Set(color)
    preview.CreateInput("roughness", Sdf.ValueTypeNames.Float).Set(roughness)
    preview.CreateInput("metallic", Sdf.ValueTypeNames.Float).Set(metallic)
    material.CreateSurfaceOutput().ConnectToSource(preview.ConnectableAPI(), "surface")

# One mesh per material, welded, decimated, with crease-split vertex normals.
before = after = 0
for path in [p.GetPath() for p in stage.Traverse() if p.IsA(UsdGeom.Mesh) and UsdGeom.Imageable(p).ComputePurpose() == "default"]:
    p = stage.GetPrimAtPath(path)
    mesh = UsdGeom.Mesh(p)
    points = np.array(mesh.GetPointsAttr().Get(), dtype=np.float64)
    counts = np.array(mesh.GetFaceVertexCountsAttr().Get())
    assert (counts == 3).all(), p.GetPath()
    faces = np.array(mesh.GetFaceVertexIndicesAttr().Get()).reshape(-1, 3)
    groups = {}
    for subset in UsdGeom.Subset.GetAllGeomSubsets(mesh):
        bound = UsdShade.MaterialBindingAPI(subset.GetPrim()).ComputeBoundMaterial()[0]
        groups.setdefault(str(bound.GetPath()), []).append(np.array(subset.GetIndicesAttr().Get()))
    assigned = np.concatenate([i for v in groups.values() for i in v]) if groups else np.array([], int)
    rest = np.setdiff1d(np.arange(len(faces)), assigned)
    if len(rest):
        bound = UsdShade.MaterialBindingAPI(p).ComputeBoundMaterial()[0]
        groups.setdefault(str(bound.GetPath()) if bound else None, []).append(rest)
    parent, base_name = p.GetParent().GetPath(), p.GetName()
    local = UsdGeom.Xformable(p).GetLocalTransformation()
    ru.remove(layer, p.GetPath())
    for k, (material, parts) in enumerate(sorted(groups.items(), key=lambda kv: str(kv[0]))):
        idx = np.concatenate(parts)
        pts, fcs = ru.weld(points, faces[idx])
        used, remap = np.unique(fcs, return_inverse=True)
        pts, fcs = pts[used], remap.reshape(-1, 3)
        before += len(fcs)
        if len(fcs) > 200:
            pts, fcs = fast_simplification.simplify(pts.astype(np.float32), fcs.astype(np.int32), target_reduction=1 - KEEP)
            pts = pts.astype(np.float64)
        after += len(fcs)
        pts, fcs, normals = ru.crease_normals(pts, np.asarray(fcs, dtype=np.int64))
        name = base_name if len(groups) == 1 else f"{base_name}_{k}"
        made = ru.author_mesh(stage, str(parent.AppendChild(name)), pts, fcs, normals, material)
        made.AddTransformOp().Set(local)

# The trail tips, where the URDF puts them. Bodies may use other frame conventions than the URDF
# links, so the URDF is placed by a best fit of every shared link origin.
rest = ru.urdf_fk(URDF, {})
cache = UsdGeom.XformCache()
names = {p.GetName(): p for p in stage.Traverse() if p.HasAPI(UsdPhysics.RigidBodyAPI)}
shared = [l for l in rest if l in names]
src = np.array([rest[l][:3, 3] for l in shared])
dst = np.array([ru.np_matrix(cache.GetLocalToWorldTransform(names[l]))[:3, 3] for l in shared])
cs, cd = src.mean(0), dst.mean(0)
U, _, Vt = np.linalg.svd((src - cs).T @ (dst - cd))
R = (U @ Vt).T
if np.linalg.det(R) < 0:
    Vt[-1] *= -1
    R = (U @ Vt).T
align = np.eye(4)
align[:3, :3] = R
align[:3, 3] = cd - R @ cs
for side in SIDES:
    ru.add_frame(stage, f"{root}/openarm_{side}_hand", f"openarm_{side}_hand_tcp", align @ rest[f"openarm_{side}_hand_tcp"])

layer.documentation = (
    "OpenArm bimanual for LeRobot. Modified by LeRobot from NVIDIA Isaac Sim 6.0 Robots/OpenArm/openarm_bimanual "
    "(Apache-2.0): flattened into one layer; sensors, render settings and colliders removed; the ee_tcp bodies "
    "replaced by the URDF's hand_tcp frames; link7-to-hand joints made fixed and renamed, and the body link renamed, "
    "to match the openarm_bimanual URDF; OmniPBR materials converted to UsdPreviewSurface; visual meshes decimated."
)
layer.customLayerData = {
    "lerobot:source": "https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/6.0/Isaac/Robots/OpenArm/openarm_bimanual/openarm_bimanual.usd",
    "lerobot:urdf": "https://huggingface.co/buckets/lerobot/robot-urdfs/resolve/openarm/openarm_bimanual_web.urdf",
}
layer.Export(OUT)

out = Usd.Stage.Open(OUT)
report = ru.check_against_urdf(out, URDF)
report["visual_bounds_vs_source_mm"] = ru.compare_visual_bounds(Usd.Stage.Open(SOURCE), out, {"openarm_body_link": "openarm_body_link0"})
report["triangles"] = {"before": before, "after": after}
report["meshes"] = sum(1 for p in out.Traverse() if p.IsA(UsdGeom.Mesh))
report["fit_residual_mm"] = float(np.abs((R @ src.T).T + align[:3, 3] - dst).max() * 1000)
print(json.dumps(report, indent=1, default=str))