Imported from nvidia/skills (skills/i4h-catheter-navigation-render-drr/SKILL.md). Install upstream with npx skills add nvidia/skills --skill i4h-catheter-navigation-render-drr. Copyright stays with the author (Apache-2.0).

i4h Catheter Navigation - Render DRR

Purpose

Render a single digitally reconstructed radiograph (DRR) frame. Works with a preprocessed CT cache from [[i4h-catheter-navigation-digital-twin]], a direct NIfTI/DICOM path, or the built-in synthetic phantom (no data required).

Base Code

ROOT="${I4H_WORKFLOWS:-$(git rev-parse --show-toplevel 2>/dev/null)}"
if [ ! -d "$ROOT/workflows/catheter_navigation" ]; then
  ROOT="${I4H_WORKFLOWS:-$HOME/i4h-workflows}"
  [ -d "$ROOT/workflows/catheter_navigation" ] || git clone https://github.com/isaac-for-healthcare/i4h-workflows "$ROOT"
fi
export I4H_WORKFLOWS="$ROOT"; cd "$ROOT"

Basics

• Default mode in metadata.json; self-contained with synthetic phantom when no --cache is given.
• GPU + slangpy required for actual rendering.
• Entry mode: ./i4h run catheter_navigation render_drr (preferred).

Run

Run the steps below in order. Each step is a separate bash call; variables persist in the local agent's tmux session.

Step 1 - resolve run dir

REPO_ROOT="${I4H_WORKFLOWS:-$(git rev-parse --show-toplevel 2>/dev/null)}"; [ -d "$REPO_ROOT/workflows/catheter_navigation" ] || REPO_ROOT="$HOME/i4h-workflows"
WF_ROOT="${REPO_ROOT}/workflows/catheter_navigation"
RUN_DIR="${WF_ROOT}/runs/render_drr_$(date +%Y%m%d_%H%M%S)"
mkdir -p "${RUN_DIR}/logs"
ln -sfn "${RUN_DIR}" "${WF_ROOT}/runs/.latest"
OUTPUT="${RUN_DIR}/drr.png"
CACHE="${CACHE:-}"

Step 2 - render (pick one variant)

Synthetic phantom (fastest smoke, no data):

"${REPO_ROOT}/i4h" run catheter_navigation render_drr --local \
  --run-args="--output ${OUTPUT}" \
  2>&1 | tee "${RUN_DIR}/logs/render_drr.log"

From preprocessed cache:

if [ ! -d "${CACHE}" ] || [ ! -f "${CACHE}/mu_volume.npy" ]; then
  echo "render-drr: set CACHE to a preprocess_ct output dir (missing mu_volume.npy)." >&2
  exit 1
fi
"${REPO_ROOT}/i4h" run catheter_navigation render_drr --local \
  --run-args="--cache ${CACHE} --output ${OUTPUT}" \
  2>&1 | tee "${RUN_DIR}/logs/render_drr.log"

Verify

test -f "${OUTPUT}"
file "${OUTPUT}"

Prerequisites

• [[i4h-catheter-navigation-setup]] completed.
• NVIDIA GPU with slangpy for rendering (CPU smoke tests do not cover GPU render).

Limitations

• Single-frame render only; batch multi-env RL rendering uses the fluorosim Python API directly.
• Catheter compositing in DRR requires attaching a CatheterProvider in custom scripts (not the default example).

Troubleshooting

• Error: slangpy / CUDA failures - Fix: run without --local to use Docker, or verify GPU driver >= 570 and CUDA 12.8.
• Error: cache not found - Fix: run [[i4h-catheter-navigation-digital-twin]] first or use synthetic mode (no --cache).

Final Response

Report output PNG path, whether synthetic or patient cache was used, and log path. Recommend [[i4h-catheter-navigation-viewport]] for interactive navigation.