utils/general_utils.py

#
# Copyright (C) 2023, Inria
# GRAPHDECO research group, https://team.inria.fr/graphdeco
# All rights reserved.
#
# This software is free for non-commercial, research and evaluation use 
# under the terms of the LICENSE.md file.
#
# For inquiries contact  [email protected]
#

import torch
import sys
from datetime import datetime
import numpy as np
import random

def inverse_sigmoid(x):
    return torch.log(x/(1-x))

def PILtoTorch(pil_image, resolution):
    resized_image_PIL = pil_image.resize(resolution)
    resized_image = torch.from_numpy(np.array(resized_image_PIL)) / 255.0
    if len(resized_image.shape) == 3:
        return resized_image.permute(2, 0, 1)
    else:
        return resized_image.unsqueeze(dim=-1).permute(2, 0, 1)

def get_expon_lr_func(
    lr_init, lr_final, lr_delay_steps=0, lr_delay_mult=1.0, max_steps=1000000
):
    """
    Copied from Plenoxels

    Continuous learning rate decay function. Adapted from JaxNeRF
    The returned rate is lr_init when step=0 and lr_final when step=max_steps, and
    is log-linearly interpolated elsewhere (equivalent to exponential decay).
    If lr_delay_steps>0 then the learning rate will be scaled by some smooth
    function of lr_delay_mult, such that the initial learning rate is
    lr_init*lr_delay_mult at the beginning of optimization but will be eased back
    to the normal learning rate when steps>lr_delay_steps.
    :param conf: config subtree 'lr' or similar
    :param max_steps: int, the number of steps during optimization.
    :return HoF which takes step as input
    """

    def helper(step):
        if step < 0 or (lr_init == 0.0 and lr_final == 0.0):
            # Disable this parameter
            return 0.0
        if lr_delay_steps > 0:
            # A kind of reverse cosine decay.
            delay_rate = lr_delay_mult + (1 - lr_delay_mult) * np.sin(
                0.5 * np.pi * np.clip(step / lr_delay_steps, 0, 1)
            )
        else:
            delay_rate = 1.0
        t = np.clip(step / max_steps, 0, 1)
        log_lerp = np.exp(np.log(lr_init) * (1 - t) + np.log(lr_final) * t)
        return delay_rate * log_lerp

    return helper

def strip_lowerdiag(L):
    uncertainty = torch.zeros((L.shape[0], 6), dtype=torch.float, device="cuda")

    uncertainty[:, 0] = L[:, 0, 0]
    uncertainty[:, 1] = L[:, 0, 1]
    uncertainty[:, 2] = L[:, 0, 2]
    uncertainty[:, 3] = L[:, 1, 1]
    uncertainty[:, 4] = L[:, 1, 2]
    uncertainty[:, 5] = L[:, 2, 2]
    return uncertainty

def strip_symmetric(sym):
    return strip_lowerdiag(sym)

def standardize_quaternion(quaternions: torch.Tensor) -> torch.Tensor:
    """
    From Pytorch3d
    Convert a unit quaternion to a standard form: one in which the real
    part is non negative.

    Args:
        quaternions: Quaternions with real part first,
            as tensor of shape (..., 4).

    Returns:
        Standardized quaternions as tensor of shape (..., 4).
    """
    return torch.where(quaternions[..., 0:1] < 0, -quaternions, quaternions)

def quaternion_raw_multiply(a: torch.Tensor, b: torch.Tensor) -> torch.Tensor:
    """
    From Pytorch3d
    Multiply two quaternions.
    Usual torch rules for broadcasting apply.

    Args:
        a: Quaternions as tensor of shape (..., 4), real part first.
        b: Quaternions as tensor of shape (..., 4), real part first.

    Returns:
        The product of a and b, a tensor of quaternions shape (..., 4).
    """
    aw, ax, ay, az = torch.unbind(a, -1)
    bw, bx, by, bz = torch.unbind(b, -1)
    ow = aw * bw - ax * bx - ay * by - az * bz
    ox = aw * bx + ax * bw + ay * bz - az * by
    oy = aw * by - ax * bz + ay * bw + az * bx
    oz = aw * bz + ax * by - ay * bx + az * bw
    return torch.stack((ow, ox, oy, oz), -1)

# Matrix to quaternion does not come under NVIDIA Copyright
# Written by Stan Szymanowicz 2023
def matrix_to_quaternion(M: torch.Tensor) -> torch.Tensor:
    """
    Matrix-to-quaternion conversion method. Equation taken from 
    https://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm
    Args:
        M: rotation matrices, (3 x 3)
    Returns:
        q: quaternion of shape (4)
    """
    tr = 1 + M[ 0, 0] + M[ 1, 1] + M[ 2, 2]

    if tr > 0:
        r = torch.sqrt(tr) / 2.0
        x = ( M[ 2, 1] - M[ 1, 2] ) / ( 4 * r )
        y = ( M[ 0, 2] - M[ 2, 0] ) / ( 4 * r )
        z = ( M[ 1, 0] - M[ 0, 1] ) / ( 4 * r )
    elif ( M[ 0, 0] > M[ 1, 1]) and (M[ 0, 0] > M[ 2, 2]):
        S = torch.sqrt(1.0 + M[ 0, 0] - M[ 1, 1] - M[ 2, 2]) * 2 # S=4*qx 
        r = (M[ 2, 1] - M[ 1, 2]) / S
        x = 0.25 * S
        y = (M[ 0, 1] + M[ 1, 0]) / S 
        z = (M[ 0, 2] + M[ 2, 0]) / S 
    elif M[ 1, 1] > M[ 2, 2]: 
        S = torch.sqrt(1.0 + M[ 1, 1] - M[ 0, 0] - M[ 2, 2]) * 2 # S=4*qy
        r = (M[ 0, 2] - M[ 2, 0]) / S
        x = (M[ 0, 1] + M[ 1, 0]) / S
        y = 0.25 * S
        z = (M[ 1, 2] + M[ 2, 1]) / S
    else:
        S = torch.sqrt(1.0 + M[ 2, 2] - M[ 0, 0] -  M[ 1, 1]) * 2 # S=4*qz
        r = (M[ 1, 0] - M[ 0, 1]) / S
        x = (M[ 0, 2] + M[ 2, 0]) / S
        y = (M[ 1, 2] + M[ 2, 1]) / S
        z = 0.25 * S

    return torch.stack([r, x, y, z], dim=-1)

def build_rotation(r):
    norm = torch.sqrt(r[:,0]*r[:,0] + r[:,1]*r[:,1] + r[:,2]*r[:,2] + r[:,3]*r[:,3])

    q = r / norm[:, None]

    R = torch.zeros((q.size(0), 3, 3), device='cuda')

    r = q[:, 0]
    x = q[:, 1]
    y = q[:, 2]
    z = q[:, 3]

    R[:, 0, 0] = 1 - 2 * (y*y + z*z)
    R[:, 0, 1] = 2 * (x*y - r*z)
    R[:, 0, 2] = 2 * (x*z + r*y)
    R[:, 1, 0] = 2 * (x*y + r*z)
    R[:, 1, 1] = 1 - 2 * (x*x + z*z)
    R[:, 1, 2] = 2 * (y*z - r*x)
    R[:, 2, 0] = 2 * (x*z - r*y)
    R[:, 2, 1] = 2 * (y*z + r*x)
    R[:, 2, 2] = 1 - 2 * (x*x + y*y)
    return R

def build_scaling_rotation(s, r):
    L = torch.zeros((s.shape[0], 3, 3), dtype=torch.float, device="cuda")
    R = build_rotation(r)

    L[:,0,0] = s[:,0]
    L[:,1,1] = s[:,1]
    L[:,2,2] = s[:,2]

    L = R @ L
    return L

def safe_state(cfg, silent=False):
    old_f = sys.stdout
    class F:
        def __init__(self, silent):
            self.silent = silent

        def write(self, x):
            if not self.silent:
                if x.endswith("\n"):
                    old_f.write(x.replace("\n", " [{}]\n".format(str(datetime.now().strftime("%d/%m %H:%M:%S")))))
                else:
                    old_f.write(x)

        def flush(self):
            old_f.flush()

    sys.stdout = F(silent)

    random.seed(cfg.general.random_seed)
    np.random.seed(cfg.general.random_seed)
    torch.manual_seed(cfg.general.random_seed)
    device = torch.device("cuda:{}".format(cfg.general.device))
    torch.cuda.set_device(device)

    return device