example_usage.py

"""
CHIP Dataset Usage Example

This script demonstrates how to load and visualize data from the CHIP dataset,
including RGB images, depth maps, camera parameters, and 3D object models.

Requirements:
    pip install datasets huggingface_hub numpy opencv-python open3d torch
"""

import json
import os
import gc
from typing import Tuple, Optional

import numpy as np
import cv2
import open3d as o3d
import torch
from datasets import load_dataset, get_dataset_infos
from huggingface_hub import snapshot_download


def lift_point_cloud(
    depth: torch.Tensor,
    camera_intrinsics: torch.Tensor,
    xy_indices: Optional[Tuple[torch.Tensor, torch.Tensor]] = None
) -> torch.Tensor:
    """
    Lift a depth image to a 3D point cloud using camera intrinsics.
    
    Args:
        depth: Depth image tensor of shape (H, W, C) where C >= 1.
               If C > 1, channels 1+ are treated as features (e.g., RGB).
        camera_intrinsics: Flattened camera intrinsic matrix [fx, 0, cx, 0, fy, cy, 0, 0, 1].
        xy_indices: Optional tuple of (x_coords, y_coords) to lift only specific pixels.
    
    Returns:
        Point cloud tensor of shape (N, 3+F) where F is the number of feature channels.
        First 3 columns are XYZ coordinates, remaining columns are features.
    """
    H, W, num_channels = depth.shape
    depth_values = depth[:, :, 0]
    
    if xy_indices is not None:
        x_coords, y_coords = xy_indices
        x_coords = x_coords.to(depth_values.device).float()
        y_coords = y_coords.to(depth_values.device).float()
        z_coords = depth_values[y_coords.long(), x_coords.long()]
    else:
        # Create pixel coordinate grids
        x_grid, y_grid = np.meshgrid(
            np.arange(W, dtype=np.float32),
            np.arange(H, dtype=np.float32),
            indexing='xy'
        )
        x_coords = torch.from_numpy(x_grid).flatten().to(depth_values.device)
        y_coords = torch.from_numpy(y_grid).flatten().to(depth_values.device)
        z_coords = depth_values.flatten()
    
    # Extract camera intrinsics
    fx, fy = camera_intrinsics[0], camera_intrinsics[4]
    cx, cy = camera_intrinsics[2], camera_intrinsics[5]
    
    # Back-project to 3D coordinates
    x_3d = (x_coords - cx) * z_coords / fx
    y_3d = (y_coords - cy) * z_coords / fy
    points_3d = torch.stack([x_3d, y_3d, z_coords], dim=1)
    
    # Add additional features (e.g., RGB) if present
    if num_channels > 1:
        features = depth[y_coords.long(), x_coords.long(), 1:]
        if xy_indices is None:
            features = features.reshape(H * W, num_channels - 1)
        points_3d = torch.cat([points_3d, features], dim=1)
    
    return points_3d


def back_project_rgbd(
    rgb: np.ndarray,
    depth: np.ndarray,
    camera_intrinsics: np.ndarray
) -> torch.Tensor:
    """
    Back-project RGB-D image to a colored point cloud.
    
    Args:
        rgb: RGB image array of shape (H, W, 3).
        depth: Depth map array of shape (H, W) with values in meters.
        camera_intrinsics: Flattened 3x3 camera intrinsic matrix.
    
    Returns:
        Point cloud tensor of shape (N, 6) with XYZ and RGB columns.
    """
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    
    # Get valid depth pixel coordinates
    valid_rows, valid_cols = np.where(depth > 0)
    xy_indices = torch.tensor(
        np.stack([valid_cols, valid_rows]),
        dtype=torch.long,
        device=device
    )
    
    # Concatenate depth and RGB channels
    depth_rgb = torch.cat([
        torch.from_numpy(depth).unsqueeze(-1),
        torch.from_numpy(rgb)
    ], dim=2).to(device)
    
    # Lift to 3D point cloud
    camera_tensor = torch.from_numpy(camera_intrinsics).to(device)
    point_cloud = lift_point_cloud(depth_rgb, camera_tensor, tuple(xy_indices))
    
    return point_cloud


def visualize_chip_sample(
    repo_id: str = "FBK-TeV/CHIP",
    target_dir: str = "./chip_data",
    num_samples: int = 1,
    show_2d: bool = False
) -> None:
    """
    Load and visualize samples from the CHIP dataset.
    
    Args:
        repo_id: Hugging Face dataset repository ID.
        target_dir: Local directory to store downloaded model files.
        num_samples: Number of samples to visualize.
        show_2d: If True, display RGB and depth images in OpenCV windows.
                 If False, only show 3D point cloud visualization.
    """
    # Display dataset information
    info = get_dataset_infos(repo_id)
    print(f"Dataset info: {info}\n")
    
    # Download 3D object models
    print("Downloading 3D models...")
    local_path = snapshot_download(
        repo_id=repo_id,
        repo_type="dataset",
        local_dir=target_dir,
        allow_patterns=["models/*"]
    )
    print(f"Models downloaded to: {local_path}\n")
    
    # Stream dataset samples
    dataset = load_dataset(repo_id, streaming=True)
    
    for idx, example in enumerate(dataset['test'].take(num_samples)):
        print(f"Processing sample {idx + 1}/{num_samples}...")
        
        # ========== Load RGB Image ==========
        rgb_image = np.array(example['image'])
        rgb_bgr = cv2.cvtColor(rgb_image, cv2.COLOR_RGB2BGR)
        
        # ========== Load Depth Map ==========
        depth_map = np.array(example['depth'], dtype=np.uint16).astype(np.float32)
        
        # Visualize depth for display
        depth_vis = cv2.normalize(depth_map, None, 0, 255, cv2.NORM_MINMAX)
        depth_vis = depth_vis.astype(np.uint8)
        
        # ========== Parse Camera Parameters ==========
        camera_params = json.loads(example['camera_params'])
        intrinsics_matrix = np.array(camera_params['cam_K']).reshape(3, 3)
        depth_scale = camera_params['depth_scale']
        
        print(f"Camera intrinsics:\n{intrinsics_matrix}")
        print(f"Depth scale: {depth_scale}")
        
        # ========== Parse Object Labels ==========
        labels = json.loads(example['labels'])
        label = labels[0]  # Process first object
        
        rotation_matrix = np.array(label['cam_R_m2c_flat']).reshape(3, 3)
        translation_vector = np.array(label['cam_t_m2c'])
        bbox = [
            label['bbox_x'],
            label['bbox_y'],
            label['bbox_width'],
            label['bbox_height']
        ]
        
        print(f"\nObject ID: {label['obj_id']}")
        print(f"Rotation matrix:\n{rotation_matrix}")
        print(f"Translation vector: {translation_vector}")
        print(f"Bounding box (x, y, w, h): {bbox}\n")
        
        # ========== Visualize 2D ==========
        if show_2d:
            x, y, w, h = bbox
            rgb_with_bbox = rgb_bgr.copy()
            cv2.rectangle(rgb_with_bbox, (x, y), (x + w, y + h), (0, 255, 0), 2)
            
            cv2.imshow("RGB Image", rgb_with_bbox)
            cv2.imshow("Depth Map", depth_vis)
            print("Displaying 2D images (press any key to continue to 3D)...")
            cv2.waitKey(0)
        
        # ========== Create 3D Point Cloud ==========
        depth_metric = depth_map * depth_scale
        point_cloud = back_project_rgbd(rgb_image, depth_metric, intrinsics_matrix.flatten())
        
        # Convert to Open3D format
        pcd_o3d = o3d.geometry.PointCloud()
        pcd_o3d.points = o3d.utility.Vector3dVector(point_cloud[:, :3].cpu().numpy())
        if point_cloud.shape[1] > 3:
            pcd_o3d.colors = o3d.utility.Vector3dVector(
                point_cloud[:, 3:].cpu().numpy() / 255.0
            )
        
        # ========== Load and Transform 3D Model ==========
        model_path = os.path.join(target_dir, "models", f"obj_{label['obj_id']:06d}.ply")
        model_mesh = o3d.io.read_triangle_mesh(model_path)
        model_mesh.paint_uniform_color([1.0, 0.0, 0.0])  # Red
        
        # Apply pose transformation
        pose_matrix = np.eye(4)
        pose_matrix[:3, :3] = rotation_matrix
        pose_matrix[:3, 3] = translation_vector
        model_mesh.transform(pose_matrix)
        
        # ========== Visualize 3D ==========
        print("Displaying 3D visualization (close window to continue)...")
        o3d.visualization.draw_geometries(
            [pcd_o3d, model_mesh],
            window_name=f"CHIP Sample {idx + 1}: Scene + Model (Red)"
        )
        
        if show_2d:
            cv2.destroyAllWindows()
        else:
            # Small delay to prevent visualization from closing too quickly
            cv2.waitKey(100)
    
    # Cleanup
    del dataset
    gc.collect()
    print("\nVisualization complete!")


if __name__ == "__main__":
    # Example usage
    
    # Option 1: Show both 2D images and 3D point cloud
    visualize_chip_sample(
        repo_id="FBK-TeV/CHIP",
        target_dir="./chip_data",
        num_samples=1,
        show_2d=True  # Display RGB and depth images
    )
    
    # Option 2: Show only 3D point cloud visualization
    # visualize_chip_sample(
    #     repo_id="FBK-TeV/CHIP",
    #     target_dir="./chip_data",
    #     num_samples=1,
    #     show_2d=False  # Skip 2D visualization
    # )