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warp.mesh_eval_velocity#

warp.mesh_eval_velocity(
id: uint64,
face: int32,
bary_u: float32,
bary_v: float32,
) → vec3f#

  • Kernel

  • Differentiable

Evaluate the interpolated velocity on a face of the warp.Mesh from barycentric coordinates.

Linearly interpolates the face’s three per-vertex velocities the same way mesh_eval_position() interpolates positions: v0 * bary_u + v1 * bary_v + v2 * (1 - bary_u - bary_v). Requires the mesh to have been constructed with a velocities array; returns a zero vector otherwise.

Parameters:

  • id – The mesh identifier

  • face – The face (triangle) index

  • bary_u – Barycentric weight of the face’s first vertex

  • bary_v – Barycentric weight of the face’s second vertex

Returns:

The interpolated velocity, or a zero vector if the mesh has no velocities.

Example

@wp.kernel
def vel_at(mesh_id: wp.uint64, out: wp.array[wp.vec3]):
    out[0] = wp.mesh_eval_velocity(mesh_id, 0, 0.25, 0.25)

points = wp.array([[0,0,0],[1,0,0],[1,1,0],[0,1,0],[0,0,1],[1,0,1],[1,1,1],[0,1,1]], dtype=wp.vec3)
indices = wp.array([0,3,2, 0,2,1,  4,5,6, 4,6,7,  0,1,5, 0,5,4,
                    2,3,7, 2,7,6,  0,4,7, 0,7,3,  1,2,6, 1,6,5], dtype=wp.int32)
velocities = wp.array(np.tile([0.0, 0.0, 1.0], (8, 1)), dtype=wp.vec3)
mesh = wp.Mesh(points=points, indices=indices, velocities=velocities)

out = wp.zeros(1, dtype=wp.vec3)
wp.launch(vel_at, dim=1, inputs=[mesh.id], outputs=[out])
print(out.numpy()[0])

[0. 0. 1.]