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warp.bvh_query_ray#

warp.bvh_query_ray(
id: uint64,
start: vec3f,
dir: vec3f,
root: int32,
) → BvhQuery#

  • Kernel

Construct a ray query against a BVH.

Returns a query that iterates over every item in the BVH whose stored bounding box is intersected by the ray. Advance the query and read each result with bvh_query_next(). start and dir are given in BVH space, i.e. the same coordinate space as the lowers/uppers arrays passed to warp.Bvh. dir need not be normalized, but the max_dist cutoff of bvh_query_next() is measured in multiples of its length, so normalize it for max_dist to be a distance in BVH-space units.

To restrict traversal to a subtree, set root to that node’s index (for a grouped BVH the group root is obtained from bvh_get_group_root()). If root is -1 (default), traversal starts at the BVH’s global root.

Parameters:

  • id – The BVH identifier

  • start – The ray origin, in BVH space

  • dir – The ray direction, in BVH space (see above on normalization)

  • root – The node to begin the query from, or -1 (default) for the BVH’s global root

Returns:

A warp.BvhQuery. It is opaque; pass it to bvh_query_next(), which writes the index of each intersected item (an index into the arrays passed to warp.Bvh) to its index argument.

Example

@wp.kernel
def cast_ray(bvh_id: wp.uint64, lowers: wp.array[wp.vec3], uppers: wp.array[wp.vec3],
             origin: wp.vec3, dir: wp.vec3, centers: wp.array[wp.vec3]):
    query = wp.bvh_query_ray(bvh_id, origin, dir)
    item = int(0)
    while wp.bvh_query_next(query, item):
        centers[item] = 0.5 * (lowers[item] + uppers[item])

lowers = wp.array([[0, 0, 0], [2, 0, 0], [4, 0, 0]], dtype=wp.vec3)
uppers = wp.array([[1, 1, 1], [3, 1, 1], [5, 1, 1]], dtype=wp.vec3)
bvh = wp.Bvh(lowers=lowers, uppers=uppers)

centers = wp.zeros(3, dtype=wp.vec3)
wp.launch(cast_ray, dim=1, inputs=[bvh.id, lowers, uppers, wp.vec3(-1.0, 0.5, 0.5), wp.vec3(1.0, 0.0, 0.0)], outputs=[centers])
print(centers.numpy().tolist())

[[0.5, 0.5, 0.5], [2.5, 0.5, 0.5], [4.5, 0.5, 0.5]]