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import torch
from torch.autograd import Variable
from torch.autograd import Function
import torch.nn as nn
from typing import Tuple
import pointnet2_cuda as pointnet2
class FurthestPointSampling(Function):
@staticmethod
def forward(ctx, xyz: torch.Tensor, npoint: int) -> torch.Tensor:
"""
Uses iterative furthest point sampling to select a set of npoint features that have the largest
minimum distance
:param ctx:
:param xyz: (B, N, 3) where N > npoint
:param npoint: int, number of features in the sampled set
:return:
output: (B, npoint) tensor containing the set
"""
assert xyz.is_contiguous()
B, N, _ = xyz.size()
output = torch.cuda.IntTensor(B, npoint)
temp = torch.cuda.FloatTensor(B, N).fill_(1e10)
pointnet2.furthest_point_sampling_wrapper(B, N, npoint, xyz, temp, output)
return output
@staticmethod
def backward(xyz, a=None):
return None, None
furthest_point_sample = FurthestPointSampling.apply
class GatherOperation(Function):
@staticmethod
def forward(ctx, features: torch.Tensor, idx: torch.Tensor) -> torch.Tensor:
"""
:param ctx:
:param features: (B, C, N)
:param idx: (B, npoint) index tensor of the features to gather
:return:
output: (B, C, npoint)
"""
assert features.is_contiguous()
assert idx.is_contiguous()
B, npoint = idx.size()
_, C, N = features.size()
output = torch.cuda.FloatTensor(B, C, npoint)
pointnet2.gather_points_wrapper(B, C, N, npoint, features, idx, output)
ctx.for_backwards = (idx, C, N)
return output
@staticmethod
def backward(ctx, grad_out):
idx, C, N = ctx.for_backwards
B, npoint = idx.size()
grad_features = Variable(torch.cuda.FloatTensor(B, C, N).zero_())
grad_out_data = grad_out.data.contiguous()
pointnet2.gather_points_grad_wrapper(B, C, N, npoint, grad_out_data, idx, grad_features.data)
return grad_features, None
gather_operation = GatherOperation.apply
class ThreeNN(Function):
@staticmethod
def forward(ctx, unknown: torch.Tensor, known: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
"""
Find the three nearest neighbors of unknown in known
:param ctx:
:param unknown: (B, N, 3)
:param known: (B, M, 3)
:return:
dist: (B, N, 3) l2 distance to the three nearest neighbors
idx: (B, N, 3) index of 3 nearest neighbors
"""
assert unknown.is_contiguous()
assert known.is_contiguous()
B, N, _ = unknown.size()
m = known.size(1)
dist2 = torch.cuda.FloatTensor(B, N, 3)
idx = torch.cuda.IntTensor(B, N, 3)
pointnet2.three_nn_wrapper(B, N, m, unknown, known, dist2, idx)
return torch.sqrt(dist2), idx
@staticmethod
def backward(ctx, a=None, b=None):
return None, None
three_nn = ThreeNN.apply
class ThreeInterpolate(Function):
@staticmethod
def forward(ctx, features: torch.Tensor, idx: torch.Tensor, weight: torch.Tensor) -> torch.Tensor:
"""
Performs weight linear interpolation on 3 features
:param ctx:
:param features: (B, C, M) Features descriptors to be interpolated from
:param idx: (B, n, 3) three nearest neighbors of the target features in features
:param weight: (B, n, 3) weights
:return:
output: (B, C, N) tensor of the interpolated features
"""
assert features.is_contiguous()
assert idx.is_contiguous()
assert weight.is_contiguous()
B, c, m = features.size()
n = idx.size(1)
ctx.three_interpolate_for_backward = (idx, weight, m)
output = torch.cuda.FloatTensor(B, c, n)
pointnet2.three_interpolate_wrapper(B, c, m, n, features, idx, weight, output)
return output
@staticmethod
def backward(ctx, grad_out: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
"""
:param ctx:
:param grad_out: (B, C, N) tensor with gradients of outputs
:return:
grad_features: (B, C, M) tensor with gradients of features
None:
None:
"""
idx, weight, m = ctx.three_interpolate_for_backward
B, c, n = grad_out.size()
grad_features = Variable(torch.cuda.FloatTensor(B, c, m).zero_())
grad_out_data = grad_out.data.contiguous()
pointnet2.three_interpolate_grad_wrapper(B, c, n, m, grad_out_data, idx, weight, grad_features.data)
return grad_features, None, None
three_interpolate = ThreeInterpolate.apply
class GroupingOperation(Function):
@staticmethod
def forward(ctx, features: torch.Tensor, idx: torch.Tensor) -> torch.Tensor:
"""
:param ctx:
:param features: (B, C, N) tensor of features to group
:param idx: (B, npoint, nsample) tensor containing the indicies of features to group with
:return:
output: (B, C, npoint, nsample) tensor
"""
assert features.is_contiguous()
assert idx.is_contiguous()
B, nfeatures, nsample = idx.size()
_, C, N = features.size()
output = torch.cuda.FloatTensor(B, C, nfeatures, nsample)
pointnet2.group_points_wrapper(B, C, N, nfeatures, nsample, features, idx, output)
ctx.for_backwards = (idx, N)
return output
@staticmethod
def backward(ctx, grad_out: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
"""
:param ctx:
:param grad_out: (B, C, npoint, nsample) tensor of the gradients of the output from forward
:return:
grad_features: (B, C, N) gradient of the features
"""
idx, N = ctx.for_backwards
B, C, npoint, nsample = grad_out.size()
grad_features = Variable(torch.cuda.FloatTensor(B, C, N).zero_())
grad_out_data = grad_out.data.contiguous()
pointnet2.group_points_grad_wrapper(B, C, N, npoint, nsample, grad_out_data, idx, grad_features.data)
return grad_features, None
grouping_operation = GroupingOperation.apply
class BallQuery(Function):
@staticmethod
def forward(ctx, radius: float, nsample: int, xyz: torch.Tensor, new_xyz: torch.Tensor) -> torch.Tensor:
"""
:param ctx:
:param radius: float, radius of the balls
:param nsample: int, maximum number of features in the balls
:param xyz: (B, N, 3) xyz coordinates of the features
:param new_xyz: (B, npoint, 3) centers of the ball query
:return:
idx: (B, npoint, nsample) tensor with the indicies of the features that form the query balls
"""
assert new_xyz.is_contiguous()
assert xyz.is_contiguous()
B, N, _ = xyz.size()
npoint = new_xyz.size(1)
idx = torch.cuda.IntTensor(B, npoint, nsample).zero_()
pointnet2.ball_query_wrapper(B, N, npoint, radius, nsample, new_xyz, xyz, idx)
return idx
@staticmethod
def backward(ctx, a=None):
return None, None, None, None
ball_query = BallQuery.apply
class QueryAndGroup(nn.Module):
def __init__(self, radius: float, nsample: int, use_xyz: bool = True):
"""
:param radius: float, radius of ball
:param nsample: int, maximum number of features to gather in the ball
:param use_xyz:
"""
super().__init__()
self.radius, self.nsample, self.use_xyz = radius, nsample, use_xyz
def forward(self, xyz: torch.Tensor, new_xyz: torch.Tensor, features: torch.Tensor = None) -> Tuple[torch.Tensor]:
"""
:param xyz: (B, N, 3) xyz coordinates of the features
:param new_xyz: (B, npoint, 3) centroids
:param features: (B, C, N) descriptors of the features
:return:
new_features: (B, 3 + C, npoint, nsample)
"""
idx = ball_query(self.radius, self.nsample, xyz, new_xyz)
xyz_trans = xyz.transpose(1, 2).contiguous()
grouped_xyz = grouping_operation(xyz_trans, idx) # (B, 3, npoint, nsample)
grouped_xyz -= new_xyz.transpose(1, 2).unsqueeze(-1)
if features is not None:
grouped_features = grouping_operation(features, idx)
if self.use_xyz:
new_features = torch.cat([grouped_xyz, grouped_features], dim=1) # (B, C + 3, npoint, nsample)
else:
new_features = grouped_features
else:
assert self.use_xyz, "Cannot have not features and not use xyz as a feature!"
new_features = grouped_xyz
return new_features
class GroupAll(nn.Module):
def __init__(self, use_xyz: bool = True):
super().__init__()
self.use_xyz = use_xyz
def forward(self, xyz: torch.Tensor, new_xyz: torch.Tensor, features: torch.Tensor = None):
"""
:param xyz: (B, N, 3) xyz coordinates of the features
:param new_xyz: ignored
:param features: (B, C, N) descriptors of the features
:return:
new_features: (B, C + 3, 1, N)
"""
grouped_xyz = xyz.transpose(1, 2).unsqueeze(2)
if features is not None:
grouped_features = features.unsqueeze(2)
if self.use_xyz:
new_features = torch.cat([grouped_xyz, grouped_features], dim=1) # (B, 3 + C, 1, N)
else:
new_features = grouped_features
else:
new_features = grouped_xyz
return new_features
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