camera_utils.py

import torch
import numpy as np


trans_t = lambda t : torch.Tensor([
    [1,0,0,0],
    [0,1,0,0],
    [0,0,1,t],
    [0,0,0,1]]).float()

trans_t2 = lambda t : torch.Tensor([
    [1,0,0,0],
    [0,1,0,t],
    [0,0,1,0],
    [0,0,0,1]]).float()

rot_phi = lambda phi : torch.Tensor([
    [1,0,0,0],
    [0,np.cos(phi),-np.sin(phi),0],
    [0,np.sin(phi), np.cos(phi),0],
    [0,0,0,1]]).float()

rot_theta = lambda th : torch.Tensor([
    [np.cos(th),0,-np.sin(th),0],
    [0,1,0,0],
    [np.sin(th),0, np.cos(th),0],
    [0,0,0,1]]).float()

rot_z = lambda z : torch.Tensor([
    [np.cos(z),-np.sin(z),0,0],
    [np.sin(z), np.cos(z),0,0],
    [0,0,1,0],
    [0,0,0,1]]).float()

def pose_spherical(theta, phi, z, radius, translate):
    c2w = trans_t(radius)
    c2w = rot_phi(phi/180.*np.pi) @ c2w
    c2w = rot_theta(theta/180.*np.pi) @ c2w
    c2w = rot_z(z/180.*np.pi) @ c2w
    c2w = trans_t2(translate) @ c2w       #the scene is not centered. The transformations above rotates the camera spirally around the origin. So here we translate the spiral.
    c2w = torch.Tensor(np.array([[-1,0,0,0],[0,0,1,0],[0,1,0,0],[0,0,0,1]])) @ c2w
    return c2w