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Improve mandelbort example (#308)

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This commit is contained in:
Max Graey
2019-01-09 18:26:31 +02:00
committed by Daniel Wirtz
parent 2ec89ee669
commit d82995c686
8 changed files with 861 additions and 353 deletions
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34
examples/mandelbrot/assembly/index.ts
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@ -5,39 +5,47 @@ const NUM_COLORS = 2048;
/** Computes a single line in the rectangle `width` x `height`. */
export function computeLine(y: u32, width: u32, height: u32, limit: u32): void {
var translateX = width / 1.6;
var translateY = height / 2.0;
var scale = 10.0 / min(3 * width, 4 * height);
var imaginary = (y - translateY) * scale;
var translateX = width * (1.0 / 1.6);
var translateY = height * (1.0 / 2.0);
var scale = 10.0 / min(3 * width, 4 * height);
var imaginary = (y - translateY) * scale;
var realOffset = translateX * scale;
var stride = (y * width) << 1;
var invLimit = 1.0 / limit;
var minIterations = min(8, limit);
for (let x: u32 = 0; x < width; ++x) {
let real = (x - translateX) * scale;
let real = x * scale - realOffset;
// Iterate until either the escape radius or iteration limit is exceeded
let ix = 0.0, iy = 0.0, ixSq: f64, iySq: f64;
let iteration: u32 = 0;
while ((ixSq = ix * ix) + (iySq = iy * iy) <= 4.0) {
let ixNew = ixSq - iySq + real;
iy = 2.0 * ix * iy + imaginary;
ix = ixNew;
ix = ixSq - iySq + real;
if (iteration >= limit) break;
++iteration;
}
// Do a few extra iterations for quick escapes to reduce error margin
for (let minIterations = min(8, limit); iteration < minIterations; ++iteration) {
while (iteration < minIterations) {
let ixNew = ix * ix - iy * iy + real;
iy = 2.0 * ix * iy + imaginary;
ix = ixNew;
++iteration;
}
// Iteration count is a discrete value in the range [0, limit] here, but we'd like it to be
// normalized in the range [0, 2047] so it maps to the gradient computed in JS.
// see also: http://linas.org/art-gallery/escape/escape.html
let frac = Math.log(Math.log(Math.sqrt(ix * ix + iy * iy))) / Math.LN2;
let icol = isFinite(frac)
? <u32>((NUM_COLORS - 1) * clamp((iteration + 1 - frac) / limit, 0.0, 1.0))
: NUM_COLORS - 1;
store<u16>((y * width + x) << 1, icol);
let col = NUM_COLORS - 1;
let sqd = ix * ix + iy * iy;
if (sqd > 1.0) {
let frac = Math.log2(0.5 * Math.log(sqd));
col = <u32>((NUM_COLORS - 1) * clamp((iteration + 1 - frac) * invLimit, 0.0, 1.0));
}
store<u16>(stride + (x << 1), col);
}
}