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warp.volume_lookup#

warp.volume_lookup(
id: uint64,
i: int32,
j: int32,
k: int32,
dtype: Any,
) → Any#

  • Kernel

Return the value of type dtype stored at the voxel with integer index-space coordinates i, j, k, without interpolation.

The lookup follows NanoVDB value resolution: inactive leaf voxels and internal tiles may carry stored inactive values that differ from the grid’s root background value. A location with no more specific stored value resolves to the background. The result is 0 if the volume does not store values of type dtype. Not differentiable; use volume_sample() for interpolated reads of floating-point scalar and vector data.

Parameters:

  • id – The id of a warp.Volume.

  • i – Voxel coordinate along the first index-space axis (may be negative).

  • j – Voxel coordinate along the second index-space axis (may be negative).

  • k – Voxel coordinate along the third index-space axis (may be negative).

  • dtype – Value type stored by the volume (see volume_sample()).

Returns:

The resolved voxel value of type dtype.

Example

@wp.kernel
def lookup(vid: wp.uint64, out: wp.array[wp.float32]):
    out[0] = wp.volume_lookup(vid, 1, 0, 0, dtype=float)

values = np.zeros((2, 2, 2), dtype=np.float32)
values[1, :, :] = 1.0  # f(i, j, k) = i
volume = wp.Volume.load_from_numpy(values, voxel_size=1.0, bg_value=0.0)
out = wp.zeros(1, dtype=wp.float32)
wp.launch(lookup, dim=1, inputs=[volume.id], outputs=[out])
print(round(float(out.numpy()[0]), 1))

1.0