KITTI-C2L-Dataset / code /scripts /visualize_projection.py
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Release KITTI-C2L v1.0.0: documented self-contained benchmark, loader and baselines
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#!/usr/bin/env python
"""Visualizes LiDAR->camera projection under ground-truth vs. decalibrated extrinsics.
For a chosen (sequence, frame), plots the LiDAR point cloud projected onto the
camera image side by side: ground truth on the left, one panel per selected
decalibration stage on the right, points colored by depth. Useful both as a
sanity check while generating the dataset and as a quick way to see how
severe each difficulty stage actually looks.
Requires the `viz` extra: pip install kitti-c2l[viz]
Usage:
# Every stage found for one frame
python scripts/visualize_projection.py --parquet data/train.parquet \\
--kitti-raw-root /path/to/KITTI --sequence 01 --frame 0 --output overlay.png
# A single specific row
python scripts/visualize_projection.py --parquet data/train.parquet \\
--kitti-raw-root /path/to/KITTI --sample-id 01_000000_stage1 --output overlay.png
# Only stages 1 and 5, for a quick easy-vs-hard comparison
python scripts/visualize_projection.py --parquet data/train.parquet \\
--kitti-raw-root /path/to/KITTI --sequence 04 --frame 3 --stages 1,5 --output overlay.png
"""
from __future__ import annotations
import argparse
import sys
from pathlib import Path
import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import numpy as np
import pyarrow.parquet as pq
sys.path.insert(0, str(Path(__file__).resolve().parent.parent / "src"))
from kitti_c2l.geometry import project_to_image, transform_points # noqa: E402
from kitti_c2l.loader.dataset import load_image, load_points_cm, row_extrinsic # noqa: E402
MIN_DEPTH_CM = 200.0
MAX_DEPTH_CM = 8000.0
def _select_rows(
table_rows: list[dict],
sample_id: str | None,
sequence: str | None,
frame: int | None,
stages: set[int] | None,
) -> list[dict]:
if sample_id is not None:
matches = [r for r in table_rows if r["sample_id"] == sample_id]
if not matches:
raise ValueError(f"No row with sample_id={sample_id!r}")
return matches
if sequence is not None and frame is not None:
matches = [r for r in table_rows if r["sequence"] == sequence and r["frame_index"] == frame]
if not matches:
raise ValueError(f"No rows for sequence={sequence!r}, frame={frame}")
if stages is not None:
matches = [r for r in matches if r["stage"] in stages]
if not matches:
raise ValueError(f"No rows for sequence={sequence!r}, frame={frame}, stages={sorted(stages)}")
return sorted(matches, key=lambda r: r["stage"])
print("No --sample-id or --sequence/--frame given; using the first row in the file.", file=sys.stderr)
return table_rows[:1]
def _project_valid(
points_cm: np.ndarray, rotation: np.ndarray, translation_cm: np.ndarray, intrinsics: np.ndarray, width: int, height: int
) -> tuple[np.ndarray, np.ndarray]:
"""Returns (pixels (M, 2), depths_cm (M,)) for points that land in-frame within the valid depth range."""
points_cam = transform_points(points_cm, rotation, translation_cm)
pixels = project_to_image(points_cam, intrinsics)
depths = points_cam[:, 2]
valid = (
(depths > MIN_DEPTH_CM)
& (depths < MAX_DEPTH_CM)
& (pixels[:, 0] >= 0)
& (pixels[:, 0] < width)
& (pixels[:, 1] >= 0)
& (pixels[:, 1] < height)
)
return pixels[valid], depths[valid]
def _plot_panel(ax, image: np.ndarray, pixels: np.ndarray, depths: np.ndarray, title: str) -> None:
ax.imshow(image)
if pixels.shape[0] > 0:
order = np.argsort(-depths) # far first, so near points draw on top
scatter = ax.scatter(
pixels[order, 0], pixels[order, 1], c=depths[order] / 100.0, cmap="turbo", s=3, alpha=0.85
)
plt.colorbar(scatter, ax=ax, fraction=0.03, pad=0.01, label="depth (m)")
ax.set_title(title, fontsize=9)
ax.axis("off")
def visualize(
parquet_path: str | Path,
kitti_raw_root: str | Path,
output_path: str | Path,
sample_id: str | None = None,
sequence: str | None = None,
frame: int | None = None,
stages: set[int] | None = None,
) -> Path:
table_rows = pq.read_table(parquet_path).to_pylist()
rows = _select_rows(table_rows, sample_id, sequence, frame, stages)
n_cols = 1 + len(rows) # ground truth + one panel per selected (sequence, frame, stage) row
fig, axes = plt.subplots(1, n_cols, figsize=(5 * n_cols, 5))
if n_cols == 1:
axes = [axes]
first_row = rows[0]
image = load_image(kitti_raw_root, first_row)
points_cm = load_points_cm(kitti_raw_root, first_row)
width, height = int(first_row["image_width"]), int(first_row["image_height"])
gt_rotation, gt_translation = row_extrinsic(first_row, use_ground_truth=True)
gt_pixels, gt_depths = _project_valid(points_cm, gt_rotation, gt_translation, np.array(first_row["camera_intrinsics"]).reshape(3, 3), width, height)
_plot_panel(axes[0], image, gt_pixels, gt_depths, f"Ground truth\nseq {first_row['sequence']} frame {first_row['frame_index']}")
for ax, row in zip(axes[1:], rows, strict=True):
rotation, translation = row_extrinsic(row, use_ground_truth=False)
intrinsics = np.array(row["camera_intrinsics"]).reshape(3, 3)
pixels, depths = _project_valid(points_cm, rotation, translation, intrinsics, width, height)
title = f"Stage {row['stage']} (±{row['stage_max_rotation_deg']:g}°/±{row['stage_max_translation_cm']:g}cm)"
_plot_panel(ax, image, pixels, depths, title)
fig.tight_layout()
output_path = Path(output_path)
output_path.parent.mkdir(parents=True, exist_ok=True)
fig.savefig(output_path, dpi=150)
plt.close(fig)
return output_path
def main() -> int:
parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument("--parquet", required=True, help="Path to a published {split}.parquet file.")
parser.add_argument("--kitti-raw-root", required=True, help="Local KITTI raw root, see README.md.")
parser.add_argument("--output", default="projection.png")
parser.add_argument("--sample-id", default=None, help="Exact sample_id, e.g. 01_000000_stage1.")
parser.add_argument("--sequence", default=None, help="Sequence id, e.g. 01. Use with --frame.")
parser.add_argument("--frame", type=int, default=None, help="0-based frame index within the sequence.")
parser.add_argument("--stages", default=None, help="Comma-separated stage ids to show, e.g. 1,5 (default: all found).")
args = parser.parse_args()
stages = {int(s) for s in args.stages.split(",")} if args.stages else None
output_path = visualize(
args.parquet,
args.kitti_raw_root,
args.output,
sample_id=args.sample_id,
sequence=args.sequence,
frame=args.frame,
stages=stages,
)
print(f"wrote {output_path}")
return 0
if __name__ == "__main__":
sys.exit(main())