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Summary:
There has historically been a lot of duplication between the coarse rasterization logic for point clouds and meshes. This diff factors out the shared logic, so coarse rasterization of point clouds and meshes share the same core logic.
Previously the only difference between the coarse rasterization kernels for points and meshes was the logic for checking whether a {point / triangle} intersects a tile in the image. We implement a generic coarse rasterization kernel that takes a set of 2D bounding boxes rather than geometric primitives; we then implement separate kernels that compute 2D bounding boxes for points and triangles.
This change does not affect the Python API at all. It also should not change any rasterization behavior, since this diff is just a refactoring of the existing logic.
I see this diff as the first in a few pieces of rasterizer refactoring. Followup diffs should do the following:
- Add a check for bin overflow in the generic coarse rasterizer kernel: allocate a global scalar to flag bin overflow which kernel worker threads can write to in case they detect bin overflow. The C++ launcher function can then check this flag after the kernel returns and issue a warning to the user in case of overflow.
- As a slightly more involved mechanism, if bin overflow is detected then the coarse kernel can continue running in order to count how many elements fall into each bin, without actually writing out their indices to the coarse output tensor. Then the actual number of entries per bin can be used to re-allocate the output tensor and re-run the coarse rasterization kernel so that bin overflow can be automatically avoided.
- The unification of the coarse and fine rasterization kernels also allows us to insert an extra CUDA kernel prior to coarse rasterization that filters out primitives outside the view frustum. This would be helpful for rendering full scenes (e.g. Matterport data) where only a small piece of the mesh is actually visible at any one time.
Reviewed By: bottler
Differential Revision: D25710361
fbshipit-source-id: 9c9dea512cb339c42adb3c92e7733fedd586ce1b