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This repository contains the example code, test results for the paper Continuous Pose for Monocular Cameras in Neural Implicit Representation. It showcase the effectiveness of optimizing monocular camera poses as a continuous function of time with neural network.

We have released the demo code, more details will be released soon, please check news for details.

We test our method on multiplte NeRF application, based on amazing code borrowed from BARF, EventNeRF and NICE-SLAM.

We also plan to try it on more application like NeRFstudio, also welcome to give it shot on your application.

BaRF results of initialize pose, BARF reuslts and our results

EventNeRF compare

NICE-SLAM compare

Regarding the environment you need nothing but numpy, torch to make it work

You can check the code block in the bottom of PoseNet.py to get some idea of how it work. In short:

from PoseNet import PoseNet 

# create a config dict
## if no imu is used, you can set min_time = 0 and max_time to number of images
## remember set activ to softplus if you calculate the derivatives
## max iterations is used to set scheduler
config = {
        'device': "cuda:0", 
        'poseNet_freq': 5,
        'layers_feat': [None,256,256,256,256,256,256,256,256],
        'skip': [4],  
        'min_time': 0,
        'max_time': 100,
        'activ': 'relu',
        'cam_lr': 1e-3,
        'use_scheduler': False
        'max_iter': 20000,
        }

# create instance
posenet = PoseNet(config)

# get a Nx3x4 pose matrix 
time = 1
est_pose = posenet.forward(time)

# add the step function after loss backward
loss.backward() # according to your implementation

posenet.step()

Since now the popularity in dense-slam is crazing and before I cleaned all messy code :(, I release a tutorial on how to using PoseNet in Splatam which is a famous Gaussian-splatting SLAM, simply using PoseNet can get results below:

• Step 0:
• Initialize the PoseNet, we basically just need the number of frames, if you do not know in your case, just put a large number here. If you want to small model, feel free to change the layers_feat

  ##### create PoseNet 
  posenet_config = { 'n_img':num_frames , 
                  'tracking': {
                            "poseNet_freq": 5, 
                            "device": "cuda:0", 
                            "layers_feat": [None,256,256,256,256,256,256,256,256],
                            "skip": [4] }
                          }
  transNet = TransNet(posenet_config)
  transNet = transNet.to(device)
  rotsNet = RotsNet(posenet_config)
  rotsNet = rotsNet.to(device)

• Step 1:

  • Change the optimizer and parameter initialization, we modify the function initialize_optimizer() to make sure the PoseNet parameters will be passed to optimizer, moreover we set the params['cam_unnorm_rots'] and params['cam_trans'] to requires_grad_(False) to avoid leaf tensor replacement issues. Note in mapping we change it back and this modificaton might be different based on your implementation in your slam-system.

  def initialize_optimizer(params, lrs_dict, tracking, transNet=None, rotsNet=None):
    lrs = lrs_dict
    if tracking:
        if transNet is not None and rotsNet is not None:
            # we do not want to update cam_unnorm_rots=0.0004 and cam_trans=0.002,
            # but we want to update the weights of the networks
            params['cam_unnorm_rots'] = torch.nn.Parameter(params['cam_unnorm_rots'].cuda().float().contiguous().requires_grad_(False))
            params['cam_trans'] = torch.nn.Parameter(params['cam_trans'].cuda().float().contiguous().requires_grad_(False))
            param_groups = [{'params': [v for k, v in params.items() if k not in ["cam_unnorm_rots","cam_trans"]]}]
            param_groups.append({'params': transNet.parameters(), 'name': "transNet", 'lr': lrs['cam_trans']})
            param_groups.append({'params': rotsNet.parameters(), 'name': "rotsNet", 'lr': lrs['cam_unnorm_rots']})
            return torch.optim.Adam(param_groups)
        else:
            return torch.optim.Adam(param_groups)
    else:
        # in mapping we want to set cam_unnorm_rots to be differentiable agai  
        params['cam_unnorm_rots'] = torch.nn.Parameter(params['cam_unnorm_rots'].cuda().float().contiguous().requires_grad_(True))
        params['cam_trans'] = torch.nn.Parameter(params['cam_trans'].cuda().float().contiguous().requires_grad_(True))
        param_groups = [{'params': [v], 'name': k, 'lr': lrs[k]} for k, v in params.items()]
        return torch.optim.Adam(param_groups, lr=0.0, eps=1e-15)

• Step 2

  • We change the main loop, note that if you want to make the difference every timestep to be continuous, you need to set the forwarp_prop to False otherwise it already calculate the candidate pose with a const speed assumption.

  • We first save the last time pose:

    if time_idx > 0:
      params = initialize_camera_pose(params, time_idx, forward_prop=config['tracking']['forward_prop'])
      current_cam_unnorm_rot_est = params['cam_unnorm_rots'][..., time_idx].detach().clone() 
      candidate_cam_tran_est = params['cam_trans'][..., time_idx].detach().clone() 
      current_cam_unnorm_rot_est_mat = rotation_conversions.quaternion_to_matrix(current_cam_unnorm_rot_est)

    By doing so after each optimization step we will multiple our new estimate pose on this. Note we convert quaternion to matrix but this is not necessary, you can directly do multiplication on quaternion since RotsNet output normalized quaternion

  • Last we calculate new pose estimation and put it back to ```params`

  rots_delta_mat = rotation_conversions.quaternion_to_matrix(rots_delta)
  rots_new_est = torch.matmul(current_cam_unnorm_rot_est_mat, rots_delta_mat) 
  params['cam_unnorm_rots'] = params['cam_unnorm_rots'].clone().detach()
  params['cam_trans'] = params['cam_trans'].clone().detach()
  params['cam_unnorm_rots'][..., time_idx] =  rotation_conversions.matrix_to_quaternion(rots_new_est)
  params['cam_trans'][..., time_idx] = (candidate_cam_tran_est + trans_delta)

  We use params['cam_unnorm_rots'] = params['cam_unnorm_rots'].clone().detach() to avoid issues of visiting graph twice.

  ---

That's it, by simply doing so we test on Replica room 0 and results we show on step 500, more results will coming out.

• Upload demo code
• Release code for showing how to implement on Splatam
• Release pip package (XD new user suspend)
• Release example on Nerfstudio
• Release mono-lego dataset
• Release code for replicate on BARF
• Release code for replicate on EventNeRF
• Release code for replicate on NICE-SLAM
• Make this page look nicer :)