@thi.ng/shader-ast-stdlib/controlflow/branches.d.ts

Function collection for modular GPGPU / shader programming with @thi.ng/shader-ast

import type { FloatTerm, Term, Type } from "@thi.ng/shader-ast";
/**
 * Utility function to create an n-ary conditional based on given float value
 * `x` in `[0,1]` range and any number of branch terms (at least 1). Returns a
 * nested ternary expression.
 *
 * @remarks
 * This function is useful for A/B testing of multiple versions of a shader,
 * e.g. the popular technique of using columns based on the `gl_FragCoord.x` and
 * dynamically computed column thresholds (defined by the number of given branch
 * terms).
 *
 * @example
 * ```ts tangle:../../export/branches.ts
 * import { float, sym, vec3 } from "@thi.ng/shader-ast";
 * import { branches } from "@thi.ng/shader-ast-stdlib";
 * import { targetGLSL } from "@thi.ng/shader-ast-glsl";
 *
 * // dummy "position" symbol (would be gl_FragCoord.x or similar)
 * const pos = sym(float(0.11));
 *
 * // serialize expression to GLSL for better legibility
 * console.log(
 *   targetGLSL()(
 *     branches(
 *       pos,
 *       // branch terms/options...
 *       // branch thresholds are automatically computed
 *       // making it trivial to add/remove terms
 *       vec3(1,0,0),
 *       vec3(1,1,0),
 *       vec3(0,1,0),
 *       vec3(0,0,1),
 *     )
 *   )
 * );
 *
 * // re-formatted result:
 * // ((_sf5 < 0.25)
 * //   ? vec3(1.0, 0.0, 0.0)
 * //   : ((_sf5 < 0.5)
 * //   ? vec3(1.0, 1.0, 0.0)
 * //   : ((_sf5 < 0.75)
 * //   ? vec3(0.0, 1.0, 0.0)
 * //   : vec3(0.0, 0.0, 1.0))))
 * ```
 *
 * @param x
 * @param a
 * @param terms
 */
export declare const branches: <T extends Type>(x: FloatTerm, a: Term<T>, ...terms: Term<T>[]) => Term<T>;
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