Bloom

/** * The two rows of emitters `bloom` looks at, and the composition they are arranged in. * * @remarks * A separate file for the reason `pbr-model/shot.ts` is: none of it is a lesson about bloom. * `main.ts` is then the two rendering features, the four sliders and the `afterStart` that switches * the pass on — which is all a reader came for. * * ## The two rows are the point * * The **back** row is Khronos's `EmissiveStrengthTest`: five unit cubes whose glTF materials all * declare the same emissive colour, `[0.1, 0.5, 0.9]`, and whose * `KHR_materials_emissive_strength` multipliers run 1x, 2x, 4x, 8x, 16x. Babylon Lite 1.27.0 reads * that extension (its `setPbrEmissive` documents emissive "values may exceed 1.0 for HDR emissive, * e.g. `KHR_materials_emissive_strength`"), so the strongest cubes — on the left from this camera — * sit far above white and are exactly what a bloom threshold is looking for. * * The **front** row is five spheres built in code, the same hue ramped over the range * `pbrMaterialDefinition`'s `emissive` accepts. That range stops at 1.0: the field is **sRGB** and * is decoded with `Color.srgbToLinear`, which clamps its input, so a hand-written ignifx material * cannot express an HDR emitter today. Both rows bloom; only the cubes can go past white. That * contrast is the honest version of "emissive surfaces bleed light", and it is why the example * ships both rather than only the model. */import { createMaterialAsset, MeshAsset, MeshRenderer, MODEL_ASSET_TYPE, Model, pbrMaterialDefinition } from "ignifx";import type { App, AssetHandle, ColorLike, ModelAsset } from "ignifx";/** How many spheres the generated row holds — one per cube in the model's row. */export const STEPS = 5;/** Black, which the frame is cleared to and the floor fades into, so bloom has something to bleed into. */export const CLEAR_COLOR: ColorLike = { r: 0, g: 0, b: 0, a: 1 };/** The floor's albedo: near-black, there only to catch the emitters' light and shadows. */export const FLOOR_COLOR: ColorLike = { r: 0.008, g: 0.01, b: 0.016, a: 1 };/** * The generated row's hue at full brightness, in sRGB; each sphere gets a fraction of it. * * @remarks * Warmer than it looks, and deliberately not a saturated orange. Bloom thresholds on **luminance**, * and luminance is 0.21R + 0.72G + 0.07B: a fully saturated red at 1.0 has a luminance of 0.21 and * would never cross a threshold the cubes clear five times over. This hue reaches about 0.46, which * is what puts the top of the sphere row just above {@link START_BLOOM}'s threshold and the bottom * of it below — the ramp is the lesson, and it has to straddle the line to show one. */const EMBER: ColorLike = { r: 1, g: 0.62, b: 0.28, a: 1 };/** The spheres' diameter, in metres. */const SPHERE_DIAMETER = 0.24;/** Metres between one sphere and the next, matched to the model's cube spacing. */const SPHERE_SPACING = 0.6;/** How high the sphere row's centres sit above the floor, in metres. */const SPHERE_HEIGHT = 0.12;/** How far towards the camera the sphere row sits, in metres. */const SPHERE_DEPTH = -0.35;/** * The scale the model is drawn at. * * @remarks * The file is authored in test units: unit cubes three units apart on a 16 x 10 reference card * (measured by `_tools/compress-model.ts`, which prints the extents on every run). At 0.2 the * cubes are 20 cm across and 60 cm apart, which is a scene rather than a diagram — and the same * spacing as the sphere row in front of it, so each sphere sits under a cube. */export const MODEL_SCALE = 0.2;/** How high the model's origin — the middle cube's centre — sits above the floor, in metres. */export const MODEL_HEIGHT = 0.74;/** How far from the camera the model's row sits, in metres. */export const MODEL_DEPTH = 0.35;/** The opening shot: the pose and the grading every capture is taken from. */export const SHOT = {  fov: 34,  yaw: 0,  pitch: 5,  distance: 4,  /**   * How far back the shot opens on a portrait canvas. The orbit camera keeps a square frame's   * width there, narrower than the landscape frame the rows were composed in, and from the   * landscape distance the outer cube and sphere of each row fall off its two edges.   */  portraitDistance: 5.2,  target: { x: 0, y: 0.42, z: 0 },  /** Low on purpose: the emissive surfaces should be what clips, not the lit geometry. */  exposure: 0.9,} as const;/** The bloom the example opens on, and what the poster shows. */export const START_BLOOM = { threshold: 0.32, weight: 0.6, kernel: 56, scale: 0.5 } as const;/** * Builds the generated row: one mesh shared by {@link STEPS} entities, one material each, emissive * ramped over the 0-1 range the material format can express. * * @param app - The app the entities and the assets belong to. */export function createSphereRow(app: App): void {  const mesh = MeshAsset.sphere(app, { diameter: SPHERE_DIAMETER, segments: 24 });  for (let step = 0; step < STEPS; step += 1) {    // Brightest on the left, under the cubes that go furthest past white.    const level = (STEPS - step) / STEPS;    const material = createMaterialAsset(      app,      pbrMaterialDefinition({        name: `bloom/ember-${String(STEPS - step)}`,        baseColor: { r: 0.07, g: 0.07, b: 0.08, a: 1 },        metallic: 0,        roughness: 0.4,        emissive: { r: EMBER.r * level, g: EMBER.g * level, b: EMBER.b * level, a: 1 },      }),      [],    );    const sphere = app.world.createEntity(`Sphere ${String(step + 1)}`);    sphere.transform.localPosition.set((step - (STEPS - 1) / 2) * SPHERE_SPACING, SPHERE_HEIGHT, SPHERE_DEPTH);    sphere.addComponent(MeshRenderer, { mesh, materials: [material], castShadows: true });  }}/** * Loads and places the back row. * * @remarks * The load is awaited **before** `app.start()`: a load that completes before the loop runs settles * at once, while one awaited afterwards waits for a frame's `PreUpdate`. * * The file ships a reference card and grid around its cubes. `materialOverrides` replaces one glTF * material by the name it carries in the file — here the card's `FlatBackdrop`, with a fully * transparent one, which takes it out of the frame and leaves this example's floor as the stage. * * @param app - The app the entity and the assets belong to. * @returns Nothing; the entity is the world's. */export async function createEmissiveRow(app: App): Promise<void> {  const cubes: AssetHandle<ModelAsset> = app.assets.load("models/emissive-strength-test.glb", {    type: MODEL_ASSET_TYPE,  });  await cubes.promise;  // `alphaMode: "blend"` with `alpha: 0` takes the card out of the frame entirely; an opaque dark  // card would still be lit, and read as five dark rectangles behind the cubes. The  // cubes keep their own materials, which is the point of overriding one glTF material by name  // rather than replacing the model.  const card = createMaterialAsset(    app,    pbrMaterialDefinition({ name: "bloom/card", baseColor: CLEAR_COLOR, alphaMode: "blend", alpha: 0 }),    [],  );  const row = app.world.createEntity("Emissive strength test");  row.transform.localPosition.set(0, MODEL_HEIGHT, MODEL_DEPTH);  row.transform.localScale.set(MODEL_SCALE, MODEL_SCALE, MODEL_SCALE);  row.addComponent(Model, {    model: cubes,    materialOverrides: { FlatBackdrop: card },    castShadows: false,    receiveShadows: false,  });}