Validation Difference GIFs

Purpose

Animate pixel differences between validation captures and golden images to quickly localize benchmark visual regressions.

Limitations

• Sensitive to tolerance settings and driver/GPU differences in captures.
• Requires existing golden image directories from a benchmark run.

Troubleshooting

Error / symptom	Cause	Solution
No golden directory	Benchmark not run with validation	Generate captures before diffing
Full-frame red diff	Tolerance too tight or lighting drift	Adjust per-channel threshold; relight scene
GIF empty	Zero changed pixels	Confirm capture and golden paths match resolution
"All frames passed" (SDG)	QA report shows no failures	Thresholds may need tightening; pass - to diff all frames
jq not found (SDG)	QA report filtering requires jq	Install jq or omit the qa_report argument to diff all frames

Generate per-camera GIF animations showing the pixel-wise difference between captured benchmark images and their golden references. Useful for debugging validation tolerance failures.

Available Scripts

Script	Purpose	Arguments
scripts/generate_diff_gifs.sh	Benchmark per-camera diff GIFs (nested Robots/ layout)	positional args per script header
scripts/sdg_tolerance_diff_gifs.sh	SDG golden-set diff GIFs (flat rgb/ layout), optionally filtered to QA-failed frames	positional args per script header

Running scripts

From agent runtimes that expose skill execution helpers, invoke helpers with run_script():

run_script("scripts/generate_diff_gifs.sh", args=[])

From a built Isaac Sim tree, run the same file with ./python.sh (Linux) or python.bat (Windows) from _build/*/release, or execute shell helpers directly when they do not require the simulator.

Prerequisites

• ImageMagick (composite, convert) must be available on PATH.
• A completed validation capture run with matching directory structure to the golden data.

Paths

Captures and golden data live under the Isaac Sim build release directory:

standalone_examples/benchmarks/validation/captures/<run_name>/
standalone_examples/benchmarks/validation/golden_data/<benchmark_name>/

Both share a parallel directory tree (e.g. Robots/Robot_0/.../front_hawk/left/camera_left/rgb/).

Usage

Find the latest capture

ls -td standalone_examples/benchmarks/validation/captures/benchmark_robots_nova_carter_ros2_*/ | head -1

Run the script

The bundled script is resolved via ${CLAUDE_SKILL_DIR}; falls back to the canonical repo path skills/validation-diff-gifs/scripts/:

bash "${CLAUDE_SKILL_DIR:-skills/validation-diff-gifs}/scripts/generate_diff_gifs.sh" \
    <captured_run_dir> \
    <golden_benchmark_dir> \
    [amplify] [fps]

Argument	Default	Description
captured_run_dir	(required)	Root of the capture run
golden_benchmark_dir	(required)	Root of the golden data for the benchmark
amplify	10	Multiply pixel differences by this factor for visibility
fps	5	Frame rate for the output GIF

Example

LATEST=$(ls -td standalone_examples/benchmarks/validation/captures/benchmark_robots_nova_carter_ros2_*/ | head -1)
GOLDEN="standalone_examples/benchmarks/validation/golden_data/benchmark_robots_nova_carter_ros2"

bash "${CLAUDE_SKILL_DIR:-skills/validation-diff-gifs}/scripts/generate_diff_gifs.sh" "$LATEST" "$GOLDEN"

Output

For each rgb/ directory under the capture, a diff_animation.gif is written alongside the captured PNGs:

<captured_run_dir>/Robots/.../front_hawk/left/camera_left/rgb/diff_animation.gif

• Black pixels = identical between captured and golden
• Brighter pixels = larger difference (amplified by the amplify factor)

SDG Golden-Set Tolerance Diffs

When production_capture_qa.py (from the data-collection-sim skill) produces a failing qa_report.json, use the SDG script to generate diffs only for the frames that tripped tolerance thresholds:

bash "${CLAUDE_SKILL_DIR:-skills/validation-diff-gifs}/scripts/sdg_tolerance_diff_gifs.sh" \
    <sdg_output_dir> \
    <sdg_golden_dir> \
    [qa_report.json] [amplify] [fps]

Argument	Default	Description
sdg_output_dir	(required)	SDG capture output (flat: rgb/, distance_to_image_plane/, etc.)
sdg_golden_dir	(required)	Golden reference with the same flat layout
qa_report.json	(optional)	Path to QA report; only failed frames are diffed. Pass - to diff all.
amplify	10	Pixel difference multiplier
fps	5	Output GIF frame rate

SDG Example (CI integration)

# After a production_capture_qa.py run exits non-zero:
SDG_OUT="/data/sdg_production_run"
SDG_GOLDEN="/data/sdg_golden/warehouse_baseline"
QA_REPORT="$SDG_OUT/qa_report.json"

bash "${CLAUDE_SKILL_DIR:-skills/validation-diff-gifs}/scripts/sdg_tolerance_diff_gifs.sh" \
    "$SDG_OUT" "$SDG_GOLDEN" "$QA_REPORT"

# Outputs:
#   /data/sdg_production_run/rgb/diff_animation.gif
#   /data/sdg_production_run/rgb/diff_failed_frames.txt
#   /data/sdg_production_run/distance_to_image_plane/diff_animation.gif

SDG Output Structure

<sdg_output_dir>/
├── rgb/
│   ├── rgb_0000.png ... rgb_0199.png
│   ├── diff_animation.gif          ← animated diff (failed frames only when filtered)
│   └── diff_failed_frames.txt      ← frame indices that tripped thresholds
├── distance_to_image_plane/
│   ├── distance_to_image_plane_0000.npy ...
│   └── diff_animation.gif          ← depth diff (grayscale)
└── qa_report.json                   ← from production_capture_qa.py

Prerequisites (SDG script)

• ImageMagick (composite, convert)
• jq (only when passing a qa_report.json)
• Python 3 with numpy (for depth .npy diffing); Pillow optional but recommended

Interpreting results

• Uniform low-level noise across the frame → rendering non-determinism (likely acceptable)
• Bright regions concentrated on object edges → sub-pixel movement differences
• Entire frame bright → wrong timestamp match or completely different camera pose
• One camera consistently worse than others → possible per-camera issue (tick rate, initialization)
• SDG: clustered failures at specific frame indices → seed-dependent pose or lighting issue