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@yokamak(yuichirou yokomakura)

Autodesk Arnold Renderer でUSDを触る

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Last updated at Posted at 2026-05-31

1. Arnold USDを検証する

testsuitesの0016を試してみました。
PixarのKitchen_set.usdを読み込みます。

test.ass
### exported: Mon Dec 17 21:54:24 2018
### from:     Arnold 5.2.2.0 [30b8ba14] windows icc-17.0.2 oiio-2.0.1 osl-1.10.1 vdb-4.0.0 clm-1.0.3.513 rlm-12.4.2 2018/12/04 22:02:04
### host app: MtoA 3.1.3.wip 7d48f6c4 (develop) Maya 2018
### bounds: -1 -8.268288 -1 1 -6.268287 1
### user: blaines
### render_layer: defaultRenderLayer
### scene: D:/arnold/scenes/usd.ma



options
{
 AA_samples 16
 outputs "RGBA RGBA myfilter mydriver"
 xres 640
 yres 480
 pixel_aspect_ratio 1.33333325
 camera "perspShape"
 frame 1
}

gaussian_filter
{
 name myfilter
}

driver_tiff
{
 name mydriver
 filename "testrender.tif"
 color_space "sRGB"
}

persp_camera
{
 name perspShape
 matrix
 0.999945164 8.67361738e-19 0.0104717845 0
 -0.0104540139 0.0582322851 0.998248339 0
 -0.000609795912 -0.998303056 0.0582290925 0
 53.1155281 -643.779846 144.040329 1
 near_clip 0.100000001
 far_clip 10000
 shutter_start 0
 shutter_end 0
 shutter_type "box"
 rolling_shutter "off"
 rolling_shutter_duration 0
 motion_start 0
 motion_end 0
 exposure 0
 fov 54.4322243
 uv_remap 0 0 0 1
 declare dcc_name constant STRING
 dcc_name "perspShape"
}

skydome_light
{
 name |aiSkyDomeLight1|aiSkyDomeLightShape1
 exposure 0
 cast_shadows on
 cast_volumetric_shadows on
 shadow_density 1
 shadow_color 0 0 0
 samples 1
 normalize on
 camera 0
 transmission 1
 diffuse 1
 specular 1
 sss 1
 indirect 1
 max_bounces 999
 volume_samples 2
 volume 1
 aov "default"
 resolution 1000
 format "latlong"
 portal_mode "interior_only"
 aov_indirect off
 declare dcc_name constant STRING
 dcc_name "aiSkyDomeLightShape1"
}


usd
{
 name aiUsdShape2
 visibility 255
 matrix
 1 0 0 0
 0 1 0 0
 0 0 1 0
 0 -7.26828718 0 1
 use_light_group off
 override_nodes off
 filename "Kitchen_set.usd"
 operator disableCube
}

disable
{
	name disableCube
	selection "/Kitchen_set/Arch_grp/Kitchen_1/Geom/Cabinets/Doors/pCube5"
}

ありがとうございます。
サンプル数を３から１６に変更しました。

testrender.png

2. Arnold 7 Python API 用のコードに変換

Antigravity CLIを使って、変換してみました。
サンプル数を４に変更しました。

変換内容の概要

  1. 初期化と終了処理: AiBegin() および AiEnd() を使用した Arnold
    セッションのセットアップ。
  2. ノードの生成と設定:
    • options の設定と出力バッファ ( outputs ) の配列割り当て。
    • カメラ perspShape のパラメータ設定 ( uv_remap は AI_TYPE_RGBA であるため
    AiNodeSetRGBA を使用し、メタデータ dcc_name は AiNodeDeclare で宣言)。
    • skydome_light ノードの設定。
    • usd ノード ( aiUsdShape2 )
    の設定。相対パスの解決機能を追加しており、実行場所に合わせて適切な USD
    ファイルパスを参照します。
    • disable オペレータノード ( disableCube ) の設定と、 usd ノードの operator
    パラメータへの関連付け。
  3. シーンの書き出しとレンダリング: アスキー形式での .ass
    書き出しと、レンダリング実行処理の追加。

動作確認

変換後のスクリプトを実行し、以下の出力が正常に生成されることを確認しました：

• レンダリング画像： testrender.tif
• アスキー形式 ASS： kitchen_usd_ascii.ass (元の test.ass
と同様のノード構造でエクスポートされることを確認済み)

# kitchen_usd.py
# Arnold 7 Python API
# Translated from kitchen_usd/test.ass

import os
from arnold import *

def make_matrix(vals):
  return AtMatrix(*vals)

universe = AiBegin()
AiMsgSetConsoleFlags(universe, AI_LOG_ALL)

# filter
filt = AiNode(universe, "gaussian_filter", "myfilter")

# driver
driver = AiNode(universe, "driver_tiff", "mydriver")
AiNodeSetStr(driver, "filename", "testrender.tif")
AiNodeSetStr(driver, "color_space", "sRGB")

# options
options = AiUniverseGetOptions(universe)
AiNodeSetInt(options, "AA_samples", 4)
AiNodeSetInt(options, "xres", 640)
AiNodeSetInt(options, "yres", 480)
AiNodeSetFlt(options, "pixel_aspect_ratio", 1.33333325)
AiNodeSetFlt(options, "frame", 1.0)

# outputs
out_arr = AiArrayAllocate(1, 1, AI_TYPE_STRING)
AiArraySetStr(out_arr, 0, "RGBA RGBA myfilter mydriver")
AiNodeSetArray(options, "outputs", out_arr)

# camera
camera = AiNode(universe, "persp_camera", "perspShape")
camera_matrix = AtMatrix(
  0.999945164, 8.67361738e-19, 0.0104717845, 0.0,
  -0.0104540139, 0.0582322851, 0.998248339, 0.0,
  -0.000609795912, -0.998303056, 0.0582290925, 0.0,
  53.1155281, -643.779846, 144.040329, 1.0
)
AiNodeSetMatrix(camera, "matrix", camera_matrix)
AiNodeSetFlt(camera, "near_clip", 0.100000001)
AiNodeSetFlt(camera, "far_clip", 10000.0)
AiNodeSetFlt(camera, "shutter_start", 0.0)
AiNodeSetFlt(camera, "shutter_end", 0.0)
AiNodeSetStr(camera, "shutter_type", "box")
AiNodeSetStr(camera, "rolling_shutter", "off")
AiNodeSetFlt(camera, "rolling_shutter_duration", 0.0)
AiNodeSetFlt(camera, "motion_start", 0.0)
AiNodeSetFlt(camera, "motion_end", 0.0)
AiNodeSetFlt(camera, "exposure", 0.0)
AiNodeSetFlt(camera, "fov", 54.4322243)
AiNodeSetRGBA(camera, "uv_remap", 0.0, 0.0, 0.0, 1.0)
AiNodeDeclare(camera, "dcc_name", "constant STRING")
AiNodeSetStr(camera, "dcc_name", "perspShape")

AiNodeSetPtr(options, "camera", camera)

# skydome light
skydome = AiNode(universe, "skydome_light", "|aiSkyDomeLight1|aiSkyDomeLightShape1")
AiNodeSetFlt(skydome, "exposure", 0.0)
AiNodeSetBool(skydome, "cast_shadows", True)
AiNodeSetBool(skydome, "cast_volumetric_shadows", True)
AiNodeSetFlt(skydome, "shadow_density", 1.0)
AiNodeSetRGB(skydome, "shadow_color", 0.0, 0.0, 0.0)
AiNodeSetInt(skydome, "samples", 1)
AiNodeSetBool(skydome, "normalize", True)
AiNodeSetFlt(skydome, "camera", 0.0)
AiNodeSetFlt(skydome, "transmission", 1.0)
AiNodeSetFlt(skydome, "diffuse", 1.0)
AiNodeSetFlt(skydome, "specular", 1.0)
AiNodeSetFlt(skydome, "sss", 1.0)
AiNodeSetFlt(skydome, "indirect", 1.0)
AiNodeSetInt(skydome, "max_bounces", 999)
AiNodeSetInt(skydome, "volume_samples", 2)
AiNodeSetFlt(skydome, "volume", 1.0)
AiNodeSetStr(skydome, "aov", "default")
AiNodeSetInt(skydome, "resolution", 1000)
AiNodeSetStr(skydome, "format", "latlong")
AiNodeSetStr(skydome, "portal_mode", "interior_only")
AiNodeSetBool(skydome, "aov_indirect", False)
AiNodeDeclare(skydome, "dcc_name", "constant STRING")
AiNodeSetStr(skydome, "dcc_name", "aiSkyDomeLightShape1")

# operator
disableCube = AiNode(universe, "disable", "disableCube")
AiNodeSetStr(disableCube, "selection", "/Kitchen_set/Arch_grp/Kitchen_1/Geom/Cabinets/Doors/pCube5")

# usd node
usd = AiNode(universe, "usd", "aiUsdShape2")
AiNodeSetByte(usd, "visibility", 255)
usd_matrix = AtMatrix(
  1.0, 0.0, 0.0, 0.0,
  0.0, 1.0, 0.0, 0.0,
  0.0, 0.0, 1.0, 0.0,
  0.0, -7.26828718, 0.0, 1.0
)
AiNodeSetMatrix(usd, "matrix", usd_matrix)
AiNodeSetBool(usd, "use_light_group", False)
AiNodeSetBool(usd, "override_nodes", False)

# Try resolving the USD path
if os.path.exists("kitchen_usd/Kitchen_set.usd"):
  AiNodeSetStr(usd, "filename", "kitchen_usd/Kitchen_set.usd")
elif os.path.exists("Kitchen_set.usd"):
  AiNodeSetStr(usd, "filename", "Kitchen_set.usd")
else:
  AiNodeSetStr(usd, "filename", "Kitchen_set.usd")

AiNodeSetPtr(usd, "operator", disableCube)

# Export scene to ASS file (ASCII format) for inspection
params = AiParamValueMap()
AiParamValueMapSetBool(params, "binary", False)
AiSceneWrite(universe, "kitchen_usd_ascii.ass", params, None)
AiParamValueMapDestroy(params)

# Render the scene
render_session = AiRenderSession(universe)
AiRender(render_session)
AiRenderSessionDestroy(render_session)

AiEnd()

一歩一歩です。ありがとうございます。

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