import numpy as np import torch import torch.nn as nn from torch.autograd import Function from torch.autograd.function import once_differentiable from torch.cuda.amp import custom_bwd, custom_fwd try: import _gridencoder as _backend except ImportError: from .backend import _backend _gridtype_to_id = { 'hash': 0, 'tiled': 1, } class _grid_encode(Function): @staticmethod @custom_fwd def forward(ctx, inputs, embeddings, offsets, per_level_scale, base_resolution, calc_grad_inputs=False, gridtype=0, align_corners=False): # inputs: [B, D], float in [0, 1] # embeddings: [sO, C], float # offsets: [L + 1], int # RETURN: [B, F], float inputs = inputs.contiguous() B, D = inputs.shape # batch size, coord dim L = offsets.shape[0] - 1 # level C = embeddings.shape[1] # embedding dim for each level S = np.log2(per_level_scale) # resolution multiplier at each level, apply log2 for later CUDA exp2f H = base_resolution # base resolution # manually handle autocast (only use half precision embeddings, inputs must be float for enough precision) # if C % 2 != 0, force float, since half for atomicAdd is very slow. if torch.is_autocast_enabled() and C % 2 == 0: embeddings = embeddings.to(torch.half) # L first, optimize cache for cuda kernel, but needs an extra permute later outputs = torch.empty(L, B, C, device=inputs.device, dtype=embeddings.dtype) if calc_grad_inputs: dy_dx = torch.empty(B, L * D * C, device=inputs.device, dtype=embeddings.dtype) else: dy_dx = None _backend.grid_encode_forward(inputs, embeddings, offsets, outputs, B, D, C, L, S, H, dy_dx, gridtype, align_corners) # permute back to [B, L * C] outputs = outputs.permute(1, 0, 2).reshape(B, L * C) ctx.save_for_backward(inputs, embeddings, offsets, dy_dx) ctx.dims = [B, D, C, L, S, H, gridtype] ctx.align_corners = align_corners return outputs @staticmethod #@once_differentiable @custom_bwd def backward(ctx, grad): inputs, embeddings, offsets, dy_dx = ctx.saved_tensors B, D, C, L, S, H, gridtype = ctx.dims align_corners = ctx.align_corners # grad: [B, L * C] --> [L, B, C] grad = grad.view(B, L, C).permute(1, 0, 2).contiguous() grad_embeddings = torch.zeros_like(embeddings) if dy_dx is not None: grad_inputs = torch.zeros_like(inputs, dtype=embeddings.dtype) else: grad_inputs = None _backend.grid_encode_backward(grad, inputs, embeddings, offsets, grad_embeddings, B, D, C, L, S, H, dy_dx, grad_inputs, gridtype, align_corners) if dy_dx is not None: grad_inputs = grad_inputs.to(inputs.dtype) return grad_inputs, grad_embeddings, None, None, None, None, None, None grid_encode = _grid_encode.apply class GridEncoder(nn.Module): def __init__(self, input_dim=3, num_levels=16, level_dim=2, per_level_scale=2, base_resolution=16, log2_hashmap_size=19, desired_resolution=None, gridtype='hash', align_corners=False): super().__init__() # the finest resolution desired at the last level, if provided, overridee per_level_scale if desired_resolution is not None: per_level_scale = np.exp2(np.log2(desired_resolution / base_resolution) / (num_levels - 1)) self.input_dim = input_dim # coord dims, 2 or 3 self.num_levels = num_levels # num levels, each level multiply resolution by 2 self.level_dim = level_dim # encode channels per level self.per_level_scale = per_level_scale # multiply resolution by this scale at each level. self.log2_hashmap_size = log2_hashmap_size self.base_resolution = base_resolution self.output_dim = num_levels * level_dim self.gridtype = gridtype self.gridtype_id = _gridtype_to_id[gridtype] # "tiled" or "hash" self.align_corners = align_corners # allocate parameters offsets = [] offset = 0 self.max_params = 2 ** log2_hashmap_size for i in range(num_levels): resolution = int(np.ceil(base_resolution * per_level_scale ** i)) params_in_level = min(self.max_params, (resolution if align_corners else resolution + 1) ** input_dim) # limit max number params_in_level = int(np.ceil(params_in_level / 8) * 8) # make divisible offsets.append(offset) offset += params_in_level offsets.append(offset) offsets = torch.from_numpy(np.array(offsets, dtype=np.int32)) self.register_buffer('offsets', offsets) self.n_params = offsets[-1] * level_dim # parameters self.embeddings = nn.Parameter(torch.empty(offset, level_dim)) self.reset_parameters() def reset_parameters(self): std = 1e-4 self.embeddings.data.uniform_(-std, std) def __repr__(self): return f"GridEncoder: input_dim={self.input_dim} num_levels={self.num_levels} level_dim={self.level_dim} resolution={self.base_resolution} -> {int(round(self.base_resolution * self.per_level_scale ** (self.num_levels - 1)))} per_level_scale={self.per_level_scale:.4f} params={tuple(self.embeddings.shape)} gridtype={self.gridtype} align_corners={self.align_corners}" def forward(self, inputs, bound=1): # inputs: [..., input_dim], normalized real world positions in [-bound, bound] # return: [..., num_levels * level_dim] inputs = (inputs + bound) / (2 * bound) # map to [0, 1] #print('inputs', inputs.shape, inputs.dtype, inputs.min().item(), inputs.max().item()) prefix_shape = list(inputs.shape[:-1]) inputs = inputs.view(-1, self.input_dim) outputs = grid_encode(inputs, self.embeddings, self.offsets, self.per_level_scale, self.base_resolution, inputs.requires_grad, self.gridtype_id, self.align_corners) outputs = outputs.view(prefix_shape + [self.output_dim]) #print('outputs', outputs.shape, outputs.dtype, outputs.min().item(), outputs.max().item()) return outputs