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USDPLY

Supported features

Feature Import Export
Scene up axis ⦸ ⦸
Scene units ⦸ ⦸
Node hierarchy ⦸ ⦸
Node transform matrix ⦸ ⦸
Node TRS ⦸ ⦸
Node animations ⦸ ⦸
Cameras ⦸ ⦸
Mesh positions ✅ ✅
Mesh normals ✅ ✅
Mesh uvs ✅ ✅
Mesh vertex colors ✅ ✅
Mesh skinning ⦸ ⦸
Mesh blend shapes ⦸ ⦸
Mesh instancing ⦸ ⦸
Mesh bounding box ⦸ ⦸
Nurbs ⦸ ⦸
Skeletons ⦸ ⦸
Skeleton Animations ⦸ ⦸
Materials ⦸ ⦸
Point cloud positions ✅ ✅
Point cloud normals ✅ ✅
Point cloud uvs ✅ ✅
Gaussian splats ✅ ✅

Translation Notes

Whether it is a mesh or a point cloud: We import UsdGeomPoints if the PLY file does not contain any facets, or the plyPoints option is on.

Whether it is a Gaussian splat: Whether the imported instance is a Gaussian splat is determined by if it contains all the Gaussian-splat-related attributes, namely, the opacity attribute specifying float-point opacities, the f_dc_* attributes specifying the float-point colors, the rot attribute specifying splats' orientations, the scale_* attributes specifying the splats' object-space sizes, and the f_rest_* specifying the splats' spherical harmonics coefficients up to 3rd orders (and thus there are f_rest_0 to f_rest_44). We map the opacity to displayOpacity, f_dc_* to displayColor and scale_0 to widths of UsdGeomPoints.

Similarly, we detect whether the exported USD file has rot, fRest*, widths1 (corresponding to scale_1) and widths2 (corresponding to scale_2) to determine if we should export a Gaussian splat.

Export: The different static and skinned meshes from USD are transformed by their local to world transform and aggregated into a single mesh because Ply lacks support for multiple individual meshes.

File Format Arguments

Import:

  • plyGsplatsClippingBox: imported Gaussian splats will be clipped with the range specified by this box, where the value is a string in the form of [-X, -Y, -Z, X, Y, Z], by default it is -2 to 2 on each axis.
  • plyPoints: Forces importing UsdGeomMesh instances as points if true. The following imports UsdGeomMesh instances as points: 
    UsdStageRefPtr stage = UsdStage::Open("cube.ply:SDF_FORMAT_ARGS:plyPoints=true")
stage->Export("cube.usd")
  • plyPointWidth: Defines the default point size, in case the instance is treated as a point cloud. The following imports UsdGeomMesh instances as points with size 0.1. 
    UsdStageRefPtr stage = UsdStage::Open("cube.ply:SDF_FORMAT_ARGS:plyPoints=true&plyPointWidth=0.1")
stage->Export("cube.usd")
  • plyWithUpAxisCorrection: Whether the imported PLY will have its axis corrected based on its comment (either explicitly has "Z-axis up" in the comment or is exported from a specific software that uses Z-axis up). If so we apply a rotation to Y-up during importing. By default it is true. The following imports UsdGeomPoints instances as Gaussian splats without axis correction (if the PLY contains all the Gaussian-splat-related attributes). 
    UsdStageRefPtr stage = UsdStage::Open("gsplat.ply:SDF_FORMAT_ARGS:plyWithUpAxisCorrection=false")
stage->Export("gsplat.usd")

Debug codes

  • FILE_FORMAT_PLY: Common debug messages.