Refactor mesh coarse rasterization

jcjohnson · facebook-github-bot · commit eed68f457d69 · 2021-09-08T16:17:30.000-07:00
Summary: Renaming parts of the mesh coarse rasterization and separating the bounding box calculation. All in preparation for sharing code with point rasterization.

Reviewed By: bottler

Differential Revision: D30369112

fbshipit-source-id: 3508c0b1239b355030cfa4038d5f3d6a945ebbf4
diff --git a/pytorch3d/csrc/rasterize_coarse/rasterize_coarse.cu b/pytorch3d/csrc/rasterize_coarse/rasterize_coarse.cu
@@ -17,44 +17,55 @@
 #include "utils/float_math.cuh"
 #include "utils/geometry_utils.cuh" // For kEpsilon -- gross
 
-// Get the xyz coordinates of the three vertices for the face given by the
-// index face_idx into face_verts.
-__device__ thrust::tuple<float3, float3, float3> GetSingleFaceVerts(
-    const float* face_verts,
-    int face_idx) {
-  const float x0 = face_verts[face_idx * 9 + 0];
-  const float y0 = face_verts[face_idx * 9 + 1];
-  const float z0 = face_verts[face_idx * 9 + 2];
-  const float x1 = face_verts[face_idx * 9 + 3];
-  const float y1 = face_verts[face_idx * 9 + 4];
-  const float z1 = face_verts[face_idx * 9 + 5];
-  const float x2 = face_verts[face_idx * 9 + 6];
-  const float y2 = face_verts[face_idx * 9 + 7];
-  const float z2 = face_verts[face_idx * 9 + 8];
-
-  const float3 v0xyz = make_float3(x0, y0, z0);
-  const float3 v1xyz = make_float3(x1, y1, z1);
-  const float3 v2xyz = make_float3(x2, y2, z2);
-
-  return thrust::make_tuple(v0xyz, v1xyz, v2xyz);
+__global__ void TriangleBoundingBoxKernel(
+    const float* face_verts, // (F, 3, 3)
+    const int F,
+    const float blur_radius,
+    float* bboxes, // (4, F)
+    bool* skip_face) { // (F,)
+  const int tid = blockIdx.x * blockDim.x + threadIdx.x;
+  const int num_threads = blockDim.x * gridDim.x;
+  const float sqrt_radius = sqrt(blur_radius);
+  for (int f = tid; f < F; f += num_threads) {
+    const float v0x = face_verts[f * 9 + 0 * 3 + 0];
+    const float v0y = face_verts[f * 9 + 0 * 3 + 1];
+    const float v0z = face_verts[f * 9 + 0 * 3 + 2];
+    const float v1x = face_verts[f * 9 + 1 * 3 + 0];
+    const float v1y = face_verts[f * 9 + 1 * 3 + 1];
+    const float v1z = face_verts[f * 9 + 1 * 3 + 2];
+    const float v2x = face_verts[f * 9 + 2 * 3 + 0];
+    const float v2y = face_verts[f * 9 + 2 * 3 + 1];
+    const float v2z = face_verts[f * 9 + 2 * 3 + 2];
+    const float xmin = FloatMin3(v0x, v1x, v2x) - sqrt_radius;
+    const float xmax = FloatMax3(v0x, v1x, v2x) + sqrt_radius;
+    const float ymin = FloatMin3(v0y, v1y, v2y) - sqrt_radius;
+    const float ymax = FloatMax3(v0y, v1y, v2y) + sqrt_radius;
+    const float zmin = FloatMin3(v0z, v1z, v2z);
+    const bool skip = zmin < kEpsilon;
+    bboxes[0 * F + f] = xmin;
+    bboxes[1 * F + f] = xmax;
+    bboxes[2 * F + f] = ymin;
+    bboxes[3 * F + f] = ymax;
+    skip_face[f] = skip;
+  }
 }
 
-__global__ void RasterizeMeshesCoarseCudaKernel(
-    const float* face_verts,
-    const int64_t* mesh_to_face_first_idx,
-    const int64_t* num_faces_per_mesh,
-    const float blur_radius,
+__global__ void RasterizeCoarseCudaKernel(
+    const float* bboxes, // (4, E) (xmin, xmax, ymin, ymax)
+    const bool* should_skip, // (E,)
+    const int64_t* elem_first_idxs,
+    const int64_t* elems_per_batch,
     const int N,
-    const int F,
+    const int E,
     const int H,
     const int W,
     const int bin_size,
     const int chunk_size,
-    const int max_faces_per_bin,
-    int* faces_per_bin,
-    int* bin_faces) {
+    const int max_elem_per_bin,
+    int* elems_per_bin,
+    int* bin_elems) {
   extern __shared__ char sbuf[];
-  const int M = max_faces_per_bin;
+  const int M = max_elem_per_bin;
   // Integer divide round up
   const int num_bins_x = 1 + (W - 1) / bin_size;
   const int num_bins_y = 1 + (H - 1) / bin_size;
@@ -71,53 +82,39 @@ __global__ void RasterizeMeshesCoarseCudaKernel(
   const float half_pix_y = NDC_y_half_range / H;
 
   // This is a boolean array of shape (num_bins_y, num_bins_x, chunk_size)
-  // stored in shared memory that will track whether each point in the chunk
+  // stored in shared memory that will track whether each elem in the chunk
   // falls into each bin of the image.
   BitMask binmask((unsigned int*)sbuf, num_bins_y, num_bins_x, chunk_size);
 
-  // Have each block handle a chunk of faces
-  const int chunks_per_batch = 1 + (F - 1) / chunk_size;
+  // Have each block handle a chunk of elements
+  const int chunks_per_batch = 1 + (E - 1) / chunk_size;
   const int num_chunks = N * chunks_per_batch;
 
   for (int chunk = blockIdx.x; chunk < num_chunks; chunk += gridDim.x) {
     const int batch_idx = chunk / chunks_per_batch; // batch index
     const int chunk_idx = chunk % chunks_per_batch;
-    const int face_start_idx = chunk_idx * chunk_size;
+    const int elem_chunk_start_idx = chunk_idx * chunk_size;
 
     binmask.block_clear();
-    const int64_t mesh_face_start_idx = mesh_to_face_first_idx[batch_idx];
-    const int64_t mesh_face_stop_idx =
-        mesh_face_start_idx + num_faces_per_mesh[batch_idx];
+    const int64_t elem_start_idx = elem_first_idxs[batch_idx];
+    const int64_t elem_stop_idx = elem_start_idx + elems_per_batch[batch_idx];
 
     // Have each thread handle a different face within the chunk
-    for (int f = threadIdx.x; f < chunk_size; f += blockDim.x) {
-      const int f_idx = face_start_idx + f;
+    for (int e = threadIdx.x; e < chunk_size; e += blockDim.x) {
+      const int e_idx = elem_chunk_start_idx + e;
 
-      // Check if face index corresponds to the mesh in the batch given by
-      // batch_idx
-      if (f_idx >= mesh_face_stop_idx || f_idx < mesh_face_start_idx) {
+      // Check that we are still within the same element of the batch
+      if (e_idx >= elem_stop_idx || e_idx < elem_start_idx) {
         continue;
       }
 
-      // Get xyz coordinates of the three face vertices.
-      const auto v012 = GetSingleFaceVerts(face_verts, f_idx);
-      const float3 v0 = thrust::get<0>(v012);
-      const float3 v1 = thrust::get<1>(v012);
-      const float3 v2 = thrust::get<2>(v012);
-
-      // Compute screen-space bbox for the triangle expanded by blur.
-      float xmin = FloatMin3(v0.x, v1.x, v2.x) - sqrt(blur_radius);
-      float ymin = FloatMin3(v0.y, v1.y, v2.y) - sqrt(blur_radius);
-      float xmax = FloatMax3(v0.x, v1.x, v2.x) + sqrt(blur_radius);
-      float ymax = FloatMax3(v0.y, v1.y, v2.y) + sqrt(blur_radius);
-      float zmin = FloatMin3(v0.z, v1.z, v2.z);
-
-      // Faces with at least one vertex behind the camera won't render
-      // correctly and should be removed or clipped before calling the
-      // rasterizer
-      if (zmin < kEpsilon) {
+      if (should_skip[e_idx]) {
         continue;
       }
+      const float xmin = bboxes[0 * E + e_idx];
+      const float xmax = bboxes[1 * E + e_idx];
+      const float ymin = bboxes[2 * E + e_idx];
+      const float ymax = bboxes[3 * E + e_idx];
 
       // Brute-force search over all bins; TODO(T54294966) something smarter.
       for (int by = 0; by < num_bins_y; ++by) {
@@ -141,39 +138,39 @@ __global__ void RasterizeMeshesCoarseCudaKernel(
 
           const bool x_overlap = (xmin <= bin_x_max) && (bin_x_min < xmax);
           if (y_overlap && x_overlap) {
-            binmask.set(by, bx, f);
+            binmask.set(by, bx, e);
           }
         }
       }
     }
     __syncthreads();
-    // Now we have processed every face in the current chunk. We need to
-    // count the number of faces in each bin so we can write the indices
+    // Now we have processed every elem in the current chunk. We need to
+    // count the number of elems in each bin so we can write the indices
     // out to global memory. We have each thread handle a different bin.
     for (int byx = threadIdx.x; byx < num_bins_y * num_bins_x;
          byx += blockDim.x) {
       const int by = byx / num_bins_x;
       const int bx = byx % num_bins_x;
       const int count = binmask.count(by, bx);
-      const int faces_per_bin_idx =
+      const int elems_per_bin_idx =
           batch_idx * num_bins_y * num_bins_x + by * num_bins_x + bx;
 
-      // This atomically increments the (global) number of faces found
+      // This atomically increments the (global) number of elems found
       // in the current bin, and gets the previous value of the counter;
       // this effectively allocates space in the bin_faces array for the
-      // faces in the current chunk that fall into this bin.
-      const int start = atomicAdd(faces_per_bin + faces_per_bin_idx, count);
+      // elems in the current chunk that fall into this bin.
+      const int start = atomicAdd(elems_per_bin + elems_per_bin_idx, count);
 
       // Now loop over the binmask and write the active bits for this bin
       // out to bin_faces.
       int next_idx = batch_idx * num_bins_y * num_bins_x * M +
           by * num_bins_x * M + bx * M + start;
-      for (int f = 0; f < chunk_size; ++f) {
-        if (binmask.get(by, bx, f)) {
+      for (int e = 0; e < chunk_size; ++e) {
+        if (binmask.get(by, bx, e)) {
           // TODO(T54296346) find the correct method for handling errors in
           // CUDA. Throw an error if num_faces_per_bin > max_faces_per_bin.
           // Either decrease bin size or increase max_faces_per_bin
-          bin_faces[next_idx] = face_start_idx + f;
+          bin_elems[next_idx] = elem_chunk_start_idx + e;
           next_idx++;
         }
       }
@@ -182,6 +179,69 @@ __global__ void RasterizeMeshesCoarseCudaKernel(
   }
 }
 
+at::Tensor RasterizeCoarseCuda(
+    const at::Tensor& bboxes,
+    const at::Tensor& should_skip,
+    const at::Tensor& elem_first_idxs,
+    const at::Tensor& elems_per_batch,
+    const std::tuple<int, int> image_size,
+    const int bin_size,
+    const int max_elems_per_bin) {
+  // Set the device for the kernel launch based on the device of the input
+  at::cuda::CUDAGuard device_guard(bboxes.device());
+  cudaStream_t stream = at::cuda::getCurrentCUDAStream();
+
+  const int H = std::get<0>(image_size);
+  const int W = std::get<1>(image_size);
+
+  const int E = bboxes.size(1);
+  const int N = elems_per_batch.size(0);
+  const int M = max_elems_per_bin;
+
+  // Integer divide round up
+  const int num_bins_y = 1 + (H - 1) / bin_size;
+  const int num_bins_x = 1 + (W - 1) / bin_size;
+
+  if (num_bins_y >= kMaxItemsPerBin || num_bins_x >= kMaxItemsPerBin) {
+    std::stringstream ss;
+    ss << "In RasterizeCoarseCuda got num_bins_y: " << num_bins_y
+       << ", num_bins_x: " << num_bins_x << ", "
+       << "; that's too many!";
+    AT_ERROR(ss.str());
+  }
+  auto opts = elems_per_batch.options().dtype(at::kInt);
+  at::Tensor elems_per_bin = at::zeros({N, num_bins_y, num_bins_x}, opts);
+  at::Tensor bin_elems = at::full({N, num_bins_y, num_bins_x, M}, -1, opts);
+
+  if (bin_elems.numel() == 0) {
+    AT_CUDA_CHECK(cudaGetLastError());
+    return bin_elems;
+  }
+
+  const int chunk_size = 512;
+  const size_t shared_size = num_bins_y * num_bins_x * chunk_size / 8;
+  const size_t blocks = 64;
+  const size_t threads = 512;
+
+  RasterizeCoarseCudaKernel<<<blocks, threads, shared_size, stream>>>(
+      bboxes.contiguous().data_ptr<float>(),
+      should_skip.contiguous().data_ptr<bool>(),
+      elem_first_idxs.contiguous().data_ptr<int64_t>(),
+      elems_per_batch.contiguous().data_ptr<int64_t>(),
+      N,
+      E,
+      H,
+      W,
+      bin_size,
+      chunk_size,
+      M,
+      elems_per_bin.data_ptr<int32_t>(),
+      bin_elems.data_ptr<int32_t>());
+
+  AT_CUDA_CHECK(cudaGetLastError());
+  return bin_elems;
+}
+
 __global__ void RasterizePointsCoarseCudaKernel(
     const float* points, // (P, 3)
     const int64_t* cloud_to_packed_first_idx, // (N)
@@ -352,55 +412,32 @@ at::Tensor RasterizeMeshesCoarseCuda(
   at::cuda::CUDAGuard device_guard(face_verts.device());
   cudaStream_t stream = at::cuda::getCurrentCUDAStream();
 
-  const int H = std::get<0>(image_size);
-  const int W = std::get<1>(image_size);
-
+  // Allocate tensors for bboxes and should_skip
   const int F = face_verts.size(0);
-  const int N = num_faces_per_mesh.size(0);
-  const int M = max_faces_per_bin;
-
-  // Integer divide round up.
-  const int num_bins_y = 1 + (H - 1) / bin_size;
-  const int num_bins_x = 1 + (W - 1) / bin_size;
-
-  if (num_bins_y >= kMaxItemsPerBin || num_bins_x >= kMaxItemsPerBin) {
-    std::stringstream ss;
-    ss << "In Coarse Rasterizer got num_bins_y: " << num_bins_y
-       << ", num_bins_x: " << num_bins_x << ", "
-       << "; that's too many!";
-    AT_ERROR(ss.str());
-  }
-  auto opts = num_faces_per_mesh.options().dtype(at::kInt);
-  at::Tensor faces_per_bin = at::zeros({N, num_bins_y, num_bins_x}, opts);
-  at::Tensor bin_faces = at::full({N, num_bins_y, num_bins_x, M}, -1, opts);
-
-  if (bin_faces.numel() == 0) {
-    AT_CUDA_CHECK(cudaGetLastError());
-    return bin_faces;
-  }
-
-  const int chunk_size = 512;
-  const size_t shared_size = num_bins_y * num_bins_x * chunk_size / 8;
-  const size_t blocks = 64;
-  const size_t threads = 512;
-
-  RasterizeMeshesCoarseCudaKernel<<<blocks, threads, shared_size, stream>>>(
+  auto float_opts = face_verts.options().dtype(at::kFloat);
+  auto bool_opts = face_verts.options().dtype(at::kBool);
+  at::Tensor bboxes = at::empty({4, F}, float_opts);
+  at::Tensor should_skip = at::empty({F}, bool_opts);
+
+  // Launch kernel to compute triangle bboxes
+  const size_t blocks = 128;
+  const size_t threads = 256;
+  TriangleBoundingBoxKernel<<<blocks, threads, 0, stream>>>(
       face_verts.contiguous().data_ptr<float>(),
-      mesh_to_face_first_idx.contiguous().data_ptr<int64_t>(),
-      num_faces_per_mesh.contiguous().data_ptr<int64_t>(),
-      blur_radius,
-      N,
       F,
-      H,
-      W,
-      bin_size,
-      chunk_size,
-      M,
-      faces_per_bin.data_ptr<int32_t>(),
-      bin_faces.data_ptr<int32_t>());
-
+      blur_radius,
+      bboxes.contiguous().data_ptr<float>(),
+      should_skip.contiguous().data_ptr<bool>());
   AT_CUDA_CHECK(cudaGetLastError());
-  return bin_faces;
+
+  return RasterizeCoarseCuda(
+      bboxes,
+      should_skip,
+      mesh_to_face_first_idx,
+      num_faces_per_mesh,
+      image_size,
+      bin_size,
+      max_faces_per_bin);
 }
 
 at::Tensor RasterizePointsCoarseCuda(
