scripts/record3d2nerf.py

#!/usr/bin/env python3

# Copyright (c) 2020-2022, NVIDIA CORPORATION.  All rights reserved.
#
# NVIDIA CORPORATION and its licensors retain all intellectual property
# and proprietary rights in and to this software, related documentation
# and any modifications thereto.  Any use, reproduction, disclosure or
# distribution of this software and related documentation without an express
# license agreement from NVIDIA CORPORATION is strictly prohibited.

import argparse
import os
from pathlib import Path

import numpy as np
import json
import copy
from pyquaternion import Quaternion
from tqdm import tqdm
from PIL import Image

def rotate_img(img_path, degree=90):
    img = Image.open(img_path)
    img = img.rotate(degree, expand=1)
    img.save(img_path, quality=100, subsampling=0)
    
def rotate_camera(c2w, degree=90):
    rad = np.deg2rad(degree)
    R = Quaternion(axis=[0, 0, -1], angle=rad)
    T = R.transformation_matrix
    return c2w @ T

def swap_axes(c2w):
    rad = np.pi / 2
    R = Quaternion(axis=[1, 0, 0], angle=rad)
    T = R.transformation_matrix
    return T @ c2w

# Automatic rescale & offset the poses.
def find_transforms_center_and_scale(raw_transforms):
    print("computing center of attention...")
    frames = raw_transforms['frames']
    for frame in frames:
        frame['transform_matrix'] = np.array(frame['transform_matrix'])

    rays_o = []
    rays_d = []
    for f in tqdm(frames):
        mf = f["transform_matrix"][0:3,:]
        rays_o.append(mf[:3,3:])
        rays_d.append(mf[:3,2:3])
    rays_o = np.asarray(rays_o)
    rays_d = np.asarray(rays_d)

    # Find the point that minimizes its distances to all rays.
    def min_line_dist(rays_o, rays_d):
        A_i = np.eye(3) - rays_d * np.transpose(rays_d, [0,2,1])
        b_i = -A_i @ rays_o
        pt_mindist = np.squeeze(-np.linalg.inv((np.transpose(A_i, [0,2,1]) @ A_i).mean(0)) @ (b_i).mean(0))
        return pt_mindist

    translation = min_line_dist(rays_o, rays_d)
    normalized_transforms = copy.deepcopy(raw_transforms)
    for f in normalized_transforms["frames"]:
        f["transform_matrix"][0:3,3] -= translation

    # Find the scale.
    avglen = 0.
    for f in normalized_transforms["frames"]:
        avglen += np.linalg.norm(f["transform_matrix"][0:3,3])
    nframes = len(normalized_transforms["frames"])
    avglen /= nframes
    print("avg camera distance from origin", avglen)
    scale = 4.0 / avglen # scale to "nerf sized"

    return translation, scale

def normalize_transforms(transforms, translation, scale):
    normalized_transforms = copy.deepcopy(transforms)
    for f in normalized_transforms["frames"]:
        f["transform_matrix"] = np.asarray(f["transform_matrix"])
        f["transform_matrix"][0:3,3] -= translation
        f["transform_matrix"][0:3,3] *= scale
        f["transform_matrix"] = f["transform_matrix"].tolist()
    return normalized_transforms

def parse_args():
    parser = argparse.ArgumentParser(description="convert a Record3D capture to nerf format transforms.json")
    parser.add_argument("--scene", default="", help="path to the Record3D capture")
    parser.add_argument("--rotate", action="store_true", help="rotate the dataset")
    parser.add_argument("--subsample", default=1, type=int, help="step size of subsampling")
    args = parser.parse_args()
    return args

if __name__ == "__main__":
    args = parse_args()
    dataset_dir = Path(args.scene)
    with open(dataset_dir / 'metadata') as f:
        metadata = json.load(f)

    frames = []
    n_images = len(list((dataset_dir / 'rgbd').glob('*.jpg')))
    poses = np.array(metadata['poses'])
    for idx in tqdm(range(n_images)):
        # Link the image.
        img_name = f'{idx}.jpg'
        img_path = dataset_dir / 'rgbd' / img_name
        
        # Rotate the image.
        if args.rotate:
            # TODO: parallelize this step with joblib.
            rotate_img(img_path)
        
        # Extract c2w.
        """ Each `pose` is a 7-element tuple which contains quaternion + world position. 
            [qx, qy, qz, qw, tx, ty, tz]
        """
        pose = poses[idx]
        q = Quaternion(x=pose[0], y=pose[1], z=pose[2], w=pose[3])
        c2w = np.eye(4)
        c2w[:3, :3] = q.rotation_matrix
        c2w[:3, -1] = [pose[4], pose[5], pose[6]]
        if args.rotate:
            c2w = rotate_camera(c2w)
            c2w = swap_axes(c2w)
        
        frames.append(
            {
                "file_path": f"./rgbd/{img_name}",
                "transform_matrix": c2w.tolist(),
            }
        )

    # Write intrinsics to `cameras.txt`.
    if not args.rotate:
        h = metadata['h']
        w = metadata['w']
        K = np.array(metadata['K']).reshape([3, 3]).T
        fx = K[0, 0]
        fy = K[1, 1]
        cx = K[0, 2]
        cy = K[1, 2]
    else:
        h = metadata['w']
        w = metadata['h']
        K = np.array(metadata['K']).reshape([3, 3]).T
        fx = K[1, 1]
        fy = K[0, 0]
        cx = K[1, 2]
        cy = h - K[0, 2]

    transforms = {}
    transforms['fl_x'] = fx
    transforms['fl_y'] = fy
    transforms['cx'] = cx
    transforms['cy'] = cy
    transforms['w'] = w
    transforms['h'] = h
    transforms['aabb_scale'] = 16
    transforms['scale'] = 1.0
    transforms['camera_angle_x'] = 2 * np.arctan(transforms['w'] / (2 * transforms['fl_x']))
    transforms['camera_angle_y'] = 2 * np.arctan(transforms['h'] / (2 * transforms['fl_y']))
    transforms['frames'] = frames

    os.makedirs(dataset_dir / 'arkit_transforms', exist_ok=True)
    with open(dataset_dir / 'arkit_transforms' / 'transforms.json', 'w') as fp:
        json.dump(transforms, fp, indent=2)

    # Normalize the poses.
    transforms['frames'] = transforms['frames'][::args.subsample]
    translation, scale = find_transforms_center_and_scale(transforms)
    normalized_transforms = normalize_transforms(transforms, translation, scale)

    output_path = dataset_dir / 'transforms.json'
    with open(output_path, "w") as outfile:
        json.dump(normalized_transforms, outfile, indent=2)