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splat

splat #

The 3D Gaussian splat file scalar; a loaded Splat is the .ply path.

The format is the standard 3DGS PLY: each vertex is one gaussian with its centre x/y/z, its colour as spherical-harmonic coefficients (f_dc_0..f_dc_2 for degree zero), opacity as a logit, log scale_0..scale_2 and the rot_0..rot_3 quaternion.

HARMONIC_DEGREE_ZERO = 0.28209479177387814 module-attribute #

The degree-zero spherical harmonic: a gaussian's colour is 0.5 + this × f_dc.

Splat #

Bases: FileScalar

A 3D Gaussian splat model as a PLY file; a loaded value is its file Path.

Analysis-only: the reconstruction output cg.ui.SplatViewer renders, produced by a recipe and never captured, so it has no platform mirror and no place in a schema.

Source code in capturegraph-lib/capturegraph/types/scalars/geometry/splat.py 
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class Splat(FileScalar, name="edu.cornell.splat.3dgs", extensions=("ply",)):
    """A 3D Gaussian splat model as a PLY file; a loaded value is its file ``Path``.

    Analysis-only: the reconstruction output ``cg.ui.SplatViewer`` renders, produced by
    a recipe and never captured, so it has no platform mirror and no place in a schema.
    """

    __slots__ = ()

    analysis_only = True

    def centers(self) -> "tuple[np.ndarray, np.ndarray]":
        """Every gaussian's centre and colour as ``(positions, colors)``.

        N×3 ``float32`` metres and N×3 ``uint8``, the colour being the degree-zero
        harmonic; what seeds another splat.

        Raises:
            ValueError: If ``self`` is not a binary little-endian PLY of gaussians.
        """
        import numpy as np

        from capturegraph.types.scalars.geometry.support.ply import vertex_columns

        columns = vertex_columns(self)
        positions = np.stack([columns["x"], columns["y"], columns["z"]], axis=1).astype(np.float32)
        harmonics = np.stack([columns[f"f_dc_{index}"] for index in range(3)], axis=1)
        colors = np.clip((0.5 + HARMONIC_DEGREE_ZERO * harmonics) * 255.0, 0, 255)
        return positions, colors.astype(np.uint8)

centers() #

Every gaussian's centre and colour as (positions, colors).

N×3 float32 metres and N×3 uint8, the colour being the degree-zero harmonic; what seeds another splat.

Raises:

Type Description
ValueError

If self is not a binary little-endian PLY of gaussians.
Source code in capturegraph-lib/capturegraph/types/scalars/geometry/splat.py 
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def centers(self) -> "tuple[np.ndarray, np.ndarray]":
    """Every gaussian's centre and colour as ``(positions, colors)``.

    N×3 ``float32`` metres and N×3 ``uint8``, the colour being the degree-zero
    harmonic; what seeds another splat.

    Raises:
        ValueError: If ``self`` is not a binary little-endian PLY of gaussians.
    """
    import numpy as np

    from capturegraph.types.scalars.geometry.support.ply import vertex_columns

    columns = vertex_columns(self)
    positions = np.stack([columns["x"], columns["y"], columns["z"]], axis=1).astype(np.float32)
    harmonics = np.stack([columns[f"f_dc_{index}"] for index in range(3)], axis=1)
    colors = np.clip((0.5 + HARMONIC_DEGREE_ZERO * harmonics) * 255.0, 0, 255)
    return positions, colors.astype(np.uint8)