@openhps/core/dist/esm/three/nodes/accessors/TextureBicubic.js

Open Hybrid Positioning System - Core component

import { add, mul, div } from '../math/OperatorNode.js';
import { floor, ceil, fract, pow } from '../math/MathNode.js';
import { Fn, float, vec2, vec4, int } from '../tsl/TSLBase.js';

// Mipped Bicubic Texture Filtering by N8
// https://www.shadertoy.com/view/Dl2SDW

const bC = 1.0 / 6.0;
const w0 = a => mul(bC, mul(a, mul(a, a.negate().add(3.0)).sub(3.0)).add(1.0));
const w1 = a => mul(bC, mul(a, mul(a, mul(3.0, a).sub(6.0))).add(4.0));
const w2 = a => mul(bC, mul(a, mul(a, mul(-3.0, a).add(3.0)).add(3.0)).add(1.0));
const w3 = a => mul(bC, pow(a, 3));
const g0 = a => w0(a).add(w1(a));
const g1 = a => w2(a).add(w3(a));

// h0 and h1 are the two offset functions
const h0 = a => add(-1.0, w1(a).div(w0(a).add(w1(a))));
const h1 = a => add(1.0, w3(a).div(w2(a).add(w3(a))));
const bicubic = (textureNode, texelSize, lod) => {
  const uv = textureNode.uvNode;
  const uvScaled = mul(uv, texelSize.zw).add(0.5);
  const iuv = floor(uvScaled);
  const fuv = fract(uvScaled);
  const g0x = g0(fuv.x);
  const g1x = g1(fuv.x);
  const h0x = h0(fuv.x);
  const h1x = h1(fuv.x);
  const h0y = h0(fuv.y);
  const h1y = h1(fuv.y);
  const p0 = vec2(iuv.x.add(h0x), iuv.y.add(h0y)).sub(0.5).mul(texelSize.xy);
  const p1 = vec2(iuv.x.add(h1x), iuv.y.add(h0y)).sub(0.5).mul(texelSize.xy);
  const p2 = vec2(iuv.x.add(h0x), iuv.y.add(h1y)).sub(0.5).mul(texelSize.xy);
  const p3 = vec2(iuv.x.add(h1x), iuv.y.add(h1y)).sub(0.5).mul(texelSize.xy);
  const a = g0(fuv.y).mul(add(g0x.mul(textureNode.sample(p0).level(lod)), g1x.mul(textureNode.sample(p1).level(lod))));
  const b = g1(fuv.y).mul(add(g0x.mul(textureNode.sample(p2).level(lod)), g1x.mul(textureNode.sample(p3).level(lod))));
  return a.add(b);
};

/**
 * Applies mipped bicubic texture filtering to the given texture node.
 *
 * @tsl
 * @function
 * @param {TextureNode} textureNode - The texture node that should be filtered.
 * @param {Node<float>} [lodNode=float(3)] - Defines the LOD to sample from.
 * @return {Node} The filtered texture sample.
 */
export const textureBicubic = /*@__PURE__*/Fn(([textureNode, lodNode = float(3)]) => {
  const fLodSize = vec2(textureNode.size(int(lodNode)));
  const cLodSize = vec2(textureNode.size(int(lodNode.add(1.0))));
  const fLodSizeInv = div(1.0, fLodSize);
  const cLodSizeInv = div(1.0, cLodSize);
  const fSample = bicubic(textureNode, vec4(fLodSizeInv, fLodSize), floor(lodNode));
  const cSample = bicubic(textureNode, vec4(cLodSizeInv, cLodSize), ceil(lodNode));
  return fract(lodNode).mix(fSample, cSample);
});