eulumdat-photweb

Photometric web representation, sampling, and 3D mesh generation for EULUMDAT/IES lighting data.

This crate extends the eulumdat library with advanced sampling and 3D visualization capabilities for photometric data.

Features

• Bilinear Interpolation: Sample intensity at any C-plane/gamma angle with smooth interpolation
• Symmetry Handling: Automatic expansion based on symmetry type (C0-C180, C90-C270, both planes, vertical axis)
• Normalized Sampling: Get intensity values normalized to 0.0-1.0 range
• 3D Mesh Generation: Generate LDC (Luminous Distribution Curve) solid meshes for 3D visualization
• Graphics-Ready Output: Flat arrays for positions, normals, and indices

Quick Start

use eulumdat::Eulumdat;
use eulumdat_photweb::PhotometricWeb;

// Load photometric data
let ldt = Eulumdat::from_file("luminaire.ldt")?;

// Create a photometric web
let web = PhotometricWeb::from(&ldt);

// Sample intensity at any angle (with bilinear interpolation)
let intensity = web.sample(45.0, 30.0);  // C=45°, γ=30°
println!("Intensity at C45/G30: {} cd/klm", intensity);

// Sample normalized (0.0 to 1.0, relative to max intensity)
let normalized = web.sample_normalized(45.0, 30.0);
println!("Normalized: {:.2}", normalized);

// Check symmetry and bounds
println!("Max intensity: {} cd/klm", web.max_intensity());
println!("Symmetry: {:?}", web.symmetry());

3D Mesh Generation

Generate photometric solids (LDC - Luminous Distribution Curve) for 3D visualization:

use eulumdat::Eulumdat;
use eulumdat_photweb::{PhotometricWeb, LdcMesh};

let ldt = Eulumdat::from_file("luminaire.ldt")?;
let web = PhotometricWeb::from(&ldt);

// Generate mesh with 5° C-plane steps, 5° gamma steps, scale=1.0
let mesh = web.generate_ldc_mesh(5.0, 5.0, 1.0);

println!("Vertices: {}", mesh.vertex_count());
println!("Triangles: {}", mesh.triangle_count());

// Get data for graphics APIs (OpenGL, WebGPU, etc.)
let positions: Vec<f32> = mesh.positions_flat();  // [x0, y0, z0, x1, y1, z1, ...]
let normals: Vec<f32> = mesh.normals_flat();      // [nx0, ny0, nz0, ...]
let indices: &[u32] = &mesh.indices;              // Triangle indices

Coordinate System

The generated mesh uses a Y-up coordinate system:

• Y axis: Up (nadir at -Y, zenith at +Y)
• X-Z plane: Horizontal
• C=0°: Along +Z axis
• C=90°: Along +X axis
• γ=0°: Nadir (straight down, -Y)
• γ=90°: Horizontal (X-Z plane)
• γ=180°: Zenith (straight up, +Y)

Symmetry Support

The PhotometricWeb automatically handles all EULUMDAT symmetry types:

You can query any angle regardless of stored symmetry:

// Even with BothPlanes symmetry (only 0-90° stored),
// you can sample the full 360° range
let i_c0 = web.sample(0.0, 45.0);
let i_c180 = web.sample(180.0, 45.0);
let i_c270 = web.sample(270.0, 45.0);
// These are automatically mirrored from stored data

Use Cases

• 3D Visualization: Generate meshes for SceneKit, Three.js, Babylon.js, etc.
• Lighting Simulation: Sample intensity at arbitrary angles for ray tracing
• Analysis Tools: Compute custom metrics by sampling the photometric distribution
• Export: Generate mesh data for CAD/BIM software

Integration Examples

With wgpu/WebGPU

let mesh = web.generate_ldc_mesh(5.0, 5.0, 1.0);

// Create vertex buffer
let vertex_data: Vec<f32> = mesh.vertices
    .iter()
    .flat_map(|v| [v.x, v.y, v.z, v.nx, v.ny, v.nz])
    .collect();

// Create index buffer
let index_data: &[u32] = &mesh.indices;

With Three.js (via WASM)

const mesh = photweb.generate_ldc_mesh(5.0, 5.0, 1.0);
const geometry = new THREE.BufferGeometry();
geometry.setAttribute('position', new THREE.Float32BufferAttribute(mesh.positions_flat(), 3));
geometry.setAttribute('normal', new THREE.Float32BufferAttribute(mesh.normals_flat(), 3));
geometry.setIndex(Array.from(mesh.indices));

Related Crates

• eulumdat - Core EULUMDAT/IES parsing library
• eulumdat-cli - Command-line tool
• eulumdat-wasm - WebAssembly bindings

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.