playcanvas/build/playcanvas/src/scene/shader-lib/wgsl/chunks/render-pass/frag/sampleCatmullRom.d.ts

PlayCanvas WebGL game engine

declare const _default: "\n\nfn SampleTextureCatmullRom(tex: texture_2d<f32>, texSampler: sampler, uv: vec2f, texSize: vec2f) -> vec4f {\n    // We're going to sample a a 4x4 grid of texels surrounding the target UV coordinate. We'll do this by rounding\n    // down the sample location to get the exact center of our \"starting\" texel. The starting texel will be at\n    // location [1, 1] in the grid, where [0, 0] is the top left corner.\n    let samplePos: vec2f = uv * texSize;\n    let texPos1: vec2f = floor(samplePos - 0.5) + 0.5;\n\n    // Compute the fractional offset from our starting texel to our original sample location, which we'll\n    // feed into the Catmull-Rom spline function to get our filter weights.\n    let f: vec2f = samplePos - texPos1;\n\n    // Compute the Catmull-Rom weights using the fractional offset that we calculated earlier.\n    // These equations are pre-expanded based on our knowledge of where the texels will be located,\n    // which lets us avoid having to evaluate a piece-wise function.\n    let w0: vec2f = f * (-0.5 + f * (1.0 - 0.5 * f));\n    let w1: vec2f = 1.0 + f * f * (-2.5 + 1.5 * f);\n    let w2: vec2f = f * (0.5 + f * (2.0 - 1.5 * f));\n    let w3: vec2f = f * f * (-0.5 + 0.5 * f);\n\n    // Work out weighting factors and sampling offsets that will let us use bilinear filtering to\n    // simultaneously evaluate the middle 2 samples from the 4x4 grid.\n    let w12: vec2f = w1 + w2;\n    let offset12: vec2f = w2 / w12;\n\n    // Compute the final UV coordinates we'll use for sampling the texture\n    let texPos0: vec2f = (texPos1 - 1.0) / texSize;\n    let texPos3: vec2f = (texPos1 + 2.0) / texSize;\n    let texPos12: vec2f = (texPos1 + offset12) / texSize;\n\n    var result: vec4f = vec4f(0.0);\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos0.x, texPos0.y), 0.0) * w0.x * w0.y;\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos12.x, texPos0.y), 0.0) * w12.x * w0.y;\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos3.x, texPos0.y), 0.0) * w3.x * w0.y;\n\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos0.x, texPos12.y), 0.0) * w0.x * w12.y;\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos12.x, texPos12.y), 0.0) * w12.x * w12.y;\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos3.x, texPos12.y), 0.0) * w3.x * w12.y;\n\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos0.x, texPos3.y), 0.0) * w0.x * w3.y;\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos12.x, texPos3.y), 0.0) * w12.x * w3.y;\n    result = result + textureSampleLevel(tex, texSampler, vec2f(texPos3.x, texPos3.y), 0.0) * w3.x * w3.y;\n\n    return result;\n}\n";
export default _default;