Diffraction (Dr.Jit)

rayd.drjit diffraction API - Monte Carlo and coherent grid accumulation, explicit diffraction paths, wedge states, options, materials, and result records.

These rayd.drjit.Scene methods evaluate edge diffraction from wedge states that you supply. For a walkthrough, see Compute edge diffraction. Detached inputs return detached records; AD inputs (DfrStatesAD, DfrMaterialAD) return the ...AD records.

Scene.accum_dfr_direct #

accum_dfr_direct(states: DfrStates, grid: DfrGrid, material: DfrMaterial, options: DfrOptions = DfrOptions(), active=True) -> DfrAccum

First-order Monte Carlo diffraction onto a grid.

statesDfrStates | DfrStatesADrequired

One row per wedge and source.

gridDfrGridrequired

Receiver grid.

materialDfrMaterial | DfrMaterialADrequired

Material per scene-global primitive.

optionsDfrOptionsdefault DfrOptions()

Wave and sampling parameters.

activeBooldefault True

State mask.

acc = scene.accum_dfr_direct(states, grid, material, options)
print(acc.power, acc.direct_count)

Scene.accum_dfr #

accum_dfr(initial_states: DfrStates, recursive_states: DfrStates, grid: DfrGrid, material: DfrMaterial, options: DfrOptions = DfrOptions(), active=True) -> DfrAccum

Higher-order diffraction chains (order 2 or 3, set by options.max_order). initial_states start the chains and recursive_states supply the wedges for the later orders.

Scene.accum_dfr_coherent_direct #

accum_dfr_coherent_direct(states: DfrStates, grid: DfrGrid, material: DfrMaterial, options: DfrCoherentOptions = DfrCoherentOptions(), active=True) -> DfrCoherentAccum

Exact coherent first-order diffraction: one diffraction point per edge and cell, complex field summed coherently. No random samples and no derivatives.

Scene.build_dfr_coherent_tx_states #

build_dfr_coherent_tx_states(edges: DfrCoherentEdge, tx_position, material: DfrMaterial, options: DfrCoherentOptions = DfrCoherentOptions(), active=True) -> DfrCoherentUtdStates

Builds coherent diffraction states for the edges in edges, lit directly by a transmitter at tx_position.

Scene.build_dfr_coherent_higher_candidates #

build_dfr_coherent_higher_candidates(prev_states: DfrCoherentUtdStates, edges: DfrCoherentEdge, global_to_local_edge_index, options: DfrCoherentOptions = DfrCoherentOptions(), active=True) -> DfrCoherentCandidatePairs

Finds candidate pairs (a previous state, a next edge) for higher-order coherent chains. global_to_local_edge_index maps scene-global edge ids to rows of edges. The higher_* options set the probe radius and visibility filtering.

Scene.trace_dfr_paths #

trace_dfr_paths(tx_positions: Array3f, rx_positions: Array3f, states: DfrStates, material: DfrMaterial, options: DfrPathOptions = DfrPathOptions(), active=True) -> DfrPaths

Exports explicit diffraction paths between transmitters and receivers.

tx_positionsArray3frequired

Transmitter positions.

rx_positionsArray3frequired

Receiver positions.

statesDfrStatesrequired

Wedge states.

materialDfrMaterialrequired

Material per primitive.

optionsDfrPathOptionsdefault DfrPathOptions()

Output size and wave parameters.

activeBooldefault True

Mask.

DfrStates #

Inputs: one row per wedge and source. Construct with DfrStates() and assign the fields; set count to the row count.

Field	Default	Meaning
`count`	0	number of rows
`edge_index`	-1	edge id, for bookkeeping
`edge_pos`, `edge_dir`	zeros	edge line `edge_pos + t * edge_dir`
`edge_t_min`, `edge_t_max`	0	parameter range of the edge segment
`n0`, `n1`	zeros	normals of the two wedge faces
`prim0`, `prim1`	-1	global primitive ids of the two faces, or `-1`
`exterior_angle`	0	wedge exterior angle in radians
`src`, `src_power`	zeros, 0	source position and power illuminating the edge
`wi`, `d0`	zeros	incident and initial directions
`prefix_depth`	0	reflections before the edge

Every array default has one entry; assign arrays of length count.

DfrGrid #

AccumGrid fields (axis, position, coord0_min, coord0_max, coord1_min, coord1_max, resolution0, resolution1) plus cell_area (default 1). See AccumGrid.

DfrMaterial, DfrMaterialAD #

Same fields as Material: eta_r (1), sigma (0), mu_r (1), gain (1), valid (False), one entry per scene-global primitive.

DfrOptions #

Field	Default	Meaning
`wavelength`	1	wavelength in scene units
`k`	0	wavenumber, `2 * pi / wavelength`
`seed`	0	random seed
`samples`	0	sample count
`max_order`	1	diffraction order for `accum_dfr`
`direct_samples`, `keller_samples`, `suffix_samples`	0	samples per strategy
`strategy_mask`	3	`RAYD_DFR_DIRECT \| RAYD_DFR_KELLER \| RAYD_DFR_SUFFIX_REFL` bits
`sample_sequence`	0	`RAYD_DFR_HASH` or `RAYD_DFR_SOBOL`
`receiver_model`	0	`RAYD_DFR_MATCHED_ISO`
`collect_edge_use`	`False`	fill `edge_uses`
`collect_debug_counts`	`False`	fill the rejection counters

DfrCoherentOptions #

Field	Default	Meaning
`wavelength`, `k`	1, 0	wave parameters
`max_order`	1	coherent chain order
`receiver_model`	0	`RAYD_DFR_MATCHED_ISO`
`select_diffraction_point`	`True`	choose the diffraction point on each edge per cell
`prefilter_visibility`	`True`	apply a visibility prefilter
`collect_debug_counts`	`False`	fill the reject counters
`omega`	0	angular frequency in rad/s
`tx_pol_x`, `tx_pol_y`, `tx_pol_z`	1, 0, 0	transmitter polarization
`higher_probe_radius_scale`	0.6	probe radius scale for higher-order candidates
`higher_probe_radius_min`, `higher_probe_radius_max`	0.5, 4.0	probe radius bounds
`higher_filter_visibility`	`False`	filter higher-order candidates by visibility

DfrPathOptions #

Field	Default	Meaning
`wavelength`, `k`	1, 0	wave parameters
`seed`	0	random seed
`sample_count`	0	sample count
`max_order`	1	diffraction order
`max_paths`, `max_rx`	0	output buffer sizing
`strategy_mask`	1	`RAYD_DFR_DIRECT`
`receiver_model`	0	`RAYD_DFR_MATCHED_ISO`
`return_geom`	0	nonzero fills the geometry fields `p0` to `p2`

DfrAccum #

grid_cell_count; per cell power and complex field_x, field_y, field_z; counters direct_count, keller_count, suffix_count; rejection counters vis_rejects, edge_vis_rejects, utd_rejects; and edge_uses.

DfrCoherentAccum #

grid_cell_count; per cell complex direct_field_x, direct_field_y, direct_field_z and multi_field_x, multi_field_y, multi_field_z (higher order); counters direct_count, multi_count, visibility_reject_count, utd_reject_count.

DfrPaths #

capacity (rows) and per row: count, valid, tx_id, rx_id, order, edge0, edge1, edge2 (edges used, -1 when unused), delay (seconds), complex field_x, field_y, field_z, and diffraction points p0, p1, p2 (with return_geom).

Coherent tables #

These records feed the coherent builders. Their fields are low-level and listed here for completeness.

DfrCoherentEdge: count, edge_index, edge_pos, edge_dir, edge_line_min, edge_line_max, n0, n_face_n, wedge_n, adjacent_face0, adjacent_face1, ignore_prim_ids, ignore_k.
DfrCoherentCandidatePairs: count, prev_index, edge_index, visibility_filtered.
DfrCoherentUtdStates: count, the edge fields above, source_pos, first_interaction_pos, incident_field, incident_jones_u, incident_jones_v, path_length_prefix, order, per-face material and operator fields (face0_*, face1_*), incident basis and derivative fields, and reflection depths (prefix_reflection_depth, intermediate_reflection_depth, suffix_reflection_depth).