Mesh

Triangle mesh geometry for RayD scenes

Overview #

Mesh is the basic geometry unit in RayD. It holds triangle vertex positions and face indices, optional UV coordinates, and a transform. Meshes are added to a Scene and cannot be shared across scenes.

import rayd as rd
import drjit as dr
 
rd.set_device(0)
 
mesh = rd.Mesh(
    dr.cuda.Array3f(
        [-1.0, 1.0, 1.0, -1.0],
        [-1.0, -1.0, 1.0, 1.0],
        [0.0, 0.0, 0.0, 0.0],
    ),
    dr.cuda.Array3i([0, 0], [1, 2], [2, 3]),
)

Constructor #

rd.Mesh(v, f, uv=None, f_uv=None, verbose=False)

Parameter	Type	Description
`v`	`Array3f` or `Array3fAD`	Vertex positions. Passing `Array3fAD` attaches gradients automatically
`f`	`Array3i`	Face indices. Each column is one triangle `(v0, v1, v2)`
`uv`	`Array2f \| None`	Optional UV coordinates
`f_uv`	`Array3i \| None`	Optional UV face indices
`verbose`	`bool`	Enable verbose build logging

Properties #

Property	Description
`mesh.vertex_positions`	Get or set vertex positions. Accepts `Array3f` or `Array3fAD`
`mesh.vertex_positions_world`	Vertex positions after applying the `to_world` transform
`mesh.vertex_normals`	Per-vertex normals
`mesh.vertex_uv`	Get or set UV coordinates
`mesh.face_indices`	Get or set face indices
`mesh.face_uv_indices`	Get or set UV face indices
`mesh.to_world`	Get or set the full world transform matrix
`mesh.to_world_left`	Left factor of the transform
`mesh.to_world_right`	Right factor of the transform
`mesh.use_face_normals`	Get or set whether to use face normals instead of vertex normals
`mesh.edges_enabled`	Get or set whether edge queries are enabled for this mesh
`mesh.num_vertices`	Number of vertices
`mesh.num_faces`	Number of faces

Methods #

mesh.build() — Build the mesh's internal acceleration structure. Call after construction before adding to a scene.

mesh.set_transform(mat, set_left=True) — Set the mesh transform matrix.

mesh.append_transform(mat, append_left=True) — Multiply the current transform by mat.

mesh.secondary_edges() — Return a SecondaryEdgeInfo object containing the mesh's secondary edges for edge sampling and nearest-edge queries.

mesh.edge_indices() — Return a tuple of five arrays containing edge index data.

Differentiable Vertices #

To differentiate through mesh geometry, pass an Array3fAD as vertex positions:

verts = dr.cuda.ad.Array3f(
    [0.0, 1.0, 0.0],
    [0.0, 0.0, 1.0],
    [0.0, 0.0, 0.0],
)
dr.enable_grad(verts)
 
mesh = rd.Mesh(
    dr.cuda.Array3f([0.0, 1.0, 0.0], [0.0, 0.0, 1.0], [0.0, 0.0, 0.0]),
    dr.cuda.Array3i([0], [1], [2]),
)
mesh.vertex_positions = verts

After scene.intersect(), call dr.backward(loss) to propagate gradients back to the vertex positions.

SecondaryEdgeInfo #

mesh.secondary_edges() returns a SecondaryEdgeInfo with:

Field	Description
`start`	Edge start positions
`edge`	Edge direction vectors
`normal0`, `normal1`	Adjacent face normals
`opposite`	Opposite vertex positions
`is_boundary`	Boolean mask — `True` for boundary edges

edges = mesh.secondary_edges()
print("edge count =", edges.size())
boundary_count = sum(bool(v) for v in list(edges.is_boundary))
print("boundary edges =", boundary_count)

Next Steps #

Scene API — add meshes to a scene
Edge queries — use edge data for nearest-edge queries

Overview#

Constructor#

Properties#

Methods#

Differentiable Vertices#

SecondaryEdgeInfo#