[Feature] Add points_in_polygons CUDA op for rotated detection. (#1600)

docs/en/understand_mmcv/ops.md

@@ -20,6 +20,7 @@ We implement common CUDA ops used in detection, segmentation, etc.
 - KNN
 - MaskedConv
 - NMS
+- PointsInPolygons
 - PSAMask
 - RiRoIAlignRotated
 - RotatedFeatureAlign

docs/zh_cn/understand_mmcv/ops.md

@@ -19,6 +19,7 @@ MMCV 提供了检测、分割等任务中常用的 CUDA 算子
 - KNN
 - MaskedConv
 - NMS
+- PointsInPolygons
 - PSAMask
 - RotatedFeatureAlign
 - RoIPointPool3d

mmcv/ops/__init__.py

@@ -38,6 +38,7 @@ from .point_sample import (SimpleRoIAlign, point_sample,
                            rel_roi_point_to_rel_img_point)
 from .points_in_boxes import (points_in_boxes_all, points_in_boxes_cpu,
                               points_in_boxes_part)
+from .points_in_polygons import points_in_polygons
 from .points_sampler import PointsSampler
 from .psa_mask import PSAMask
 from .riroi_align_rotated import RiRoIAlignRotated, riroi_align_rotated
@@ -80,5 +81,6 @@ __all__ = [
     'furthest_point_sample_with_dist', 'PointsSampler', 'Correlation',
     'boxes_iou_bev', 'nms_bev', 'nms_normal_bev', 'Voxelization',
     'voxelization', 'dynamic_scatter', 'DynamicScatter', 'RoIAwarePool3d',
-    'points_in_boxes_part', 'points_in_boxes_cpu', 'points_in_boxes_all'
+    'points_in_boxes_part', 'points_in_boxes_cpu', 'points_in_boxes_all',
+    'points_in_polygons'
 ]

mmcv/ops/csrc/common/cuda/points_in_polygons_cuda_kernel.cuh

+// Copyright (c) OpenMMLab. All rights reserved
+#ifndef POINTS_IN_POLYGONS_CUDA_KERNEL_CUH
+#define POINTS_IN_POLYGONS_CUDA_KERNEL_CUH
+
+#ifdef MMCV_USE_PARROTS
+#include "parrots_cuda_helper.hpp"
+#else
+#include "pytorch_cuda_helper.hpp"
+#endif
+
+struct point {
+  float x, y;
+};
+
+template <typename scalar_t>
+__global__ void points_in_polygons_forward_cuda_kernel(
+    const int nthreads, const scalar_t *vertex1, const scalar_t *vertex2,
+    const int rows, const int cols, scalar_t *inside_flag) {
+  CUDA_1D_KERNEL_LOOP(index, nthreads) {
+    int row = index / cols;
+    int col = index % cols;
+
+    const scalar_t *offset_vertex1 = vertex1 + row * 2;
+    const scalar_t *offset_vertex2 = vertex2 + col * 8;
+
+    point point_[1];
+    point polygon[4];
+
+    point_[0].x = offset_vertex1[0];
+    point_[0].y = offset_vertex1[1];
+
+    polygon[0].x = offset_vertex2[0];
+    polygon[0].y = offset_vertex2[1];
+    polygon[1].x = offset_vertex2[2];
+    polygon[1].y = offset_vertex2[3];
+    polygon[2].x = offset_vertex2[4];
+    polygon[2].y = offset_vertex2[5];
+    polygon[3].x = offset_vertex2[6];
+    polygon[3].y = offset_vertex2[7];
+
+    int nCross = 0;
+    int i, j;
+    float sx, sy, tx, ty, px, py, x;
+    for (i = 0, j = 3; i < 4; j = i, i++) {
+      sx = polygon[i].x;
+      sy = polygon[i].y;
+      tx = polygon[j].x;
+      ty = polygon[j].y;
+
+      px = point_[0].x;
+      py = point_[0].y;
+
+      if (py < min(sy, ty)) continue;
+      if (py > max(sy, ty)) continue;
+
+      if ((sx == px && sy == py) || (tx == px && ty == py)) {
+        break;
+      } else {
+        if ((sy < py && ty >= py) || (sy >= py && ty < py)) {
+          x = sx + (py - sy) * (tx - sx) / (ty - sy);
+          if (x == px) {
+            break;
+          }
+          if (x > px) {
+            nCross++;
+          }
+        }
+      }
+    }
+    if (nCross % 2 == 1) {
+      inside_flag[index] = 1.0;
+    } else {
+      inside_flag[index] = 0.0;
+    }
+    return;
+  }
+}
+
+#endif  // POINTS_IN_POLYGONS_CUDA_KERNEL_CUH

mmcv/ops/csrc/pytorch/cuda/cudabind.cpp

@@ -1481,3 +1481,22 @@ REGISTER_DEVICE_IMPL(rotated_feature_align_forward_impl, CUDA,
                      rotated_feature_align_forward_cuda);
 REGISTER_DEVICE_IMPL(rotated_feature_align_backward_impl, CUDA,
                      rotated_feature_align_backward_cuda);
+
+void PointsInPolygonsForwardCUDAKernelLauncher(const at::Tensor points,
+                                               const at::Tensor polygons,
+                                               const int rows, const int cols,
+                                               at::Tensor output);
+
+void points_in_polygons_forward_cuda(const Tensor points, const Tensor polygons,
+                                     Tensor output, const int rows,
+                                     const int cols) {
+  PointsInPolygonsForwardCUDAKernelLauncher(points, polygons, rows, cols,
+                                            output);
+};
+
+void points_in_polygons_forward_impl(const Tensor points, const Tensor polygons,
+                                     Tensor output, const int rows,
+                                     const int cols);
+
+REGISTER_DEVICE_IMPL(points_in_polygons_forward_impl, CUDA,
+                     points_in_polygons_forward_cuda);

mmcv/ops/csrc/pytorch/cuda/points_in_polygons_cuda.cu

+// Copyright (c) OpenMMLab. All rights reserved
+// Modified from
+// https://github.com/ming71/CUDA/blob/master/point_justify/points_justify_kernel.cu
+
+#include <stdio.h>
+
+#include "points_in_polygons_cuda_kernel.cuh"
+#include "pytorch_cuda_helper.hpp"
+
+void PointsInPolygonsForwardCUDAKernelLauncher(const at::Tensor points,
+                                               const at::Tensor polygons,
+                                               const int rows, const int cols,
+                                               at::Tensor output) {
+  const int output_size = rows * cols;
+  at::cuda::CUDAGuard device_guard(points.device());
+  cudaStream_t stream = at::cuda::getCurrentCUDAStream();
+  AT_DISPATCH_FLOATING_TYPES_AND_HALF(
+      points.scalar_type(), "points_in_polygons_forward_cuda_kernel", ([&] {
+        const scalar_t *vertex1 = points.data_ptr<scalar_t>();
+        const scalar_t *vertex2 = polygons.data_ptr<scalar_t>();
+        scalar_t *inside_flag = output.data_ptr<scalar_t>();
+
+        points_in_polygons_forward_cuda_kernel<scalar_t>
+            <<<GET_BLOCKS(output_size), THREADS_PER_BLOCK, 0, stream>>>(
+                output_size, vertex1, vertex2, rows, cols, inside_flag);
+      }));
+  AT_CUDA_CHECK(cudaGetLastError());
+}

mmcv/ops/csrc/pytorch/points_in_polygons.cpp

+#include "pytorch_cpp_helper.hpp"
+#include "pytorch_device_registry.hpp"
+
+void points_in_polygons_forward_impl(const Tensor points, const Tensor polygons,
+                                     Tensor output, const int rows,
+                                     const int cols) {
+  DISPATCH_DEVICE_IMPL(points_in_polygons_forward_impl, points, polygons,
+                       output, rows, cols);
+}
+
+void points_in_polygons_forward(Tensor points, Tensor polygons, Tensor output) {
+  int rows = points.size(0);
+  int cols = polygons.size(0);
+  points_in_polygons_forward_impl(points, polygons, output, rows, cols);
+}

mmcv/ops/csrc/pytorch/pybind.cpp

@@ -361,6 +361,8 @@ void riroi_align_rotated_backward(Tensor top_grad, Tensor rois,
                                   int num_samples, int num_orientations,
                                   bool clockwise);
 
+void points_in_polygons_forward(Tensor points, Tensor polygons, Tensor output);
+
 PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
   m.def("upfirdn2d", &upfirdn2d, "upfirdn2d (CUDA)", py::arg("input"),
         py::arg("kernel"), py::arg("up_x"), py::arg("up_y"), py::arg("down_x"),
@@ -726,4 +728,7 @@ PYBIND11_MODULE(TORCH_EXTENSION_NAME, m) {
         py::arg("pooled_width"), py::arg("spatial_scale"),
         py::arg("num_samples"), py::arg("num_orientations"),
         py::arg("clockwise"));
+  m.def("points_in_polygons_forward", &points_in_polygons_forward,
+        "points_in_polygons_forward", py::arg("points"), py::arg("polygons"),
+        py::arg("output"));
 }

mmcv/ops/points_in_polygons.py

+import torch
+
+from ..utils import ext_loader
+
+ext_module = ext_loader.load_ext('_ext', ['points_in_polygons_forward'])
+
+
+def points_in_polygons(points, polygons):
+    """Judging whether points are inside polygons, which is used in the ATSS
+    assignment for the rotated boxes.
+
+    It should be noted that when the point is just at the polygon boundary, the
+    judgment will be inaccurate, but the effect on assignment is limited.
+
+    Args:
+        points (torch.Tensor): It has shape (B, 2), indicating (x, y).
+            M means the number of predicted points.
+        polygons (torch.Tensor): It has shape (M, 8), indicating
+            (x1, y1, x2, y2, x3, y3, x4, y4). M means the number of
+            ground truth polygons.
+
+    Returns:
+        torch.Tensor: Return the result with the shape of (B, M),
+        1 indicates that the point is inside the polygon,
+        0 indicates that the point is outside the polygon.
+    """
+    assert points.shape[1] == 2, \
+        'points dimension should be 2, ' \
+        f'but got unexpected shape {points.shape[1]}'
+    assert polygons.shape[1] == 8, \
+        'polygons dimension should be 8, ' \
+        f'but got unexpected shape {polygons.shape[1]}'
+    output = torch.full([points.shape[0], polygons.shape[0]],
+                        0.).cuda().float()
+    ext_module.points_in_polygons_forward(points.contiguous(),
+                                          polygons.contiguous(), output)
+    return output

tests/test_ops/test_points_in_polygons.py

+import numpy as np
+import pytest
+import torch
+
+from mmcv.ops import points_in_polygons
+
+
+@pytest.mark.skipif(
+    not torch.cuda.is_available(), reason='requires CUDA support')
+def test_points_in_polygons():
+    points = np.array([[300., 300.], [400., 400.], [100., 100], [300, 250],
+                       [100, 0]])
+    polygons = np.array([[200., 200., 400., 400., 500., 200., 400., 100.],
+                         [400., 400., 500., 500., 600., 300., 500., 200.],
+                         [300., 300., 600., 700., 700., 700., 700., 100.]])
+    expected_output = np.array([[0., 0., 0.], [0., 0., 1.], [0., 0., 0.],
+                                [1., 0., 0.], [0., 0., 0.]])
+    points = torch.from_numpy(points).cuda().float()
+    polygons = torch.from_numpy(polygons).cuda().float()
+    expected_output = torch.from_numpy(expected_output).cuda().float()
+    assert torch.allclose(
+        points_in_polygons(points, polygons), expected_output, 1e-3)