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complex optimization
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@se-ti
se-ti committed Dec 1, 2020
1 parent c5b7276 commit 0b4fbb9
Showing 1 changed file with 142 additions and 30 deletions.
172 changes: 142 additions & 30 deletions src/heatcanvas-worker.js
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Original file line number Diff line number Diff line change
Expand Up @@ -24,47 +24,159 @@ onmessage = function(e){
}

function calc(params) {
var value = params.value || {};
var degree = params.degree || 1;
var step = params.step || 1;
var value = params.value;
var degree = +params.degree || 1;
var step = +params.step || 1;

if (!Array.isArray(value)) {
value = new Array(params.width * params.height);
if (Array.prototype.fill) {
value.fill(0);
} else { // IE has no Array.fill. Poor IE
for (var i = 0, len = value.length; i < len; i++)
value[i] = 0;
}
}

var deg2 = degree / 2;

var v = 0.0, dySq = 0.0;
var scany = 0;
var scany2 = 0;
var dx = 0, rx = 0, base = 0, base2;
for (var pos in params.data) {
var data = params.data[pos] / step; // we don't need absolute values, and this allows us to get rid of many step*pow(...)
var radius = Math.floor(Math.pow(data, 1/degree));
var radius = Math.pow(data, 1/degree);
var radiusSq = Math.pow(radius, 2);
radius = Math.floor(radius);

var x = Math.floor(pos%params.width);
var y = Math.floor(pos/params.width);

// calculate point x.y
for(var scanx=x-radius; scanx<x+radius; scanx+=1){
// out of extend
if(scanx<0 || scanx>params.width){

var maxRx = params.width - 1 - x;

// for all circles, lying inside the screen use fast method
if (y >= radius && y < params.height-radius && x >= radius && radius <= maxRx) {
fastCalc(params, data, value, x, y, radius, radiusSq);
continue;
}

base = (y - radius)*params.width + x;
base2 = (y + radius)*params.width + x;

// calculate point x.y
var limDx = 0;
var limRx = x > maxRx ? x : maxRx; // maximum rx (radius for current scanline) that won't cross both (left and right) borders

var maxY = y+radius < params.height - 1 ? y+radius : (params.height - 1);
for (scany = y - radius; scany < y; scany++, base += params.width, base2 -= params.width) {
scany2 = (y + y - scany);
if (scany < 0 && scany2 > maxY) // both scanlines out of extend
continue;
}
for(var scany=y-radius; scany<y+radius; scany+=1){

if(scany<0 || scany>params.height){
continue;
}

var distSq = Math.pow((scanx-x), 2) + Math.pow((scany-y), 2);
if (distSq > radiusSq){
continue;
} else {
var v = data - Math.pow(distSq, deg2);

var id = scanx+scany*params.width ;

if(value[id]){
value[id] = value[id] + v;
} else {
value[id] = v;
}

dySq = Math.pow(scany-y, 2);
rx = Math.floor(Math.sqrt(radiusSq - dySq));

limDx = rx < maxRx ? -rx : -maxRx; // minimum dx (since dx is < 0), not to cross right border
for (dx = rx < limRx ? -rx : -limRx; dx < 0; dx++) {
v = data - Math.pow(Math.pow(dx, 2) + dySq, deg2);

if (scany >= 0) {
if (x + dx >= 0)
value[base + dx] += v;
if (dx >= limDx)
value[base - dx] += v;
}
if (scany2 <= maxY) {
if (x + dx >= 0)
value[base2 + dx] += v;
if (dx >= limDx)
value[base2 - dx] += v;
}
}
}
// dx == 0
v = data - Math.pow(dySq, deg2);
if (scany >= 0)
value[base] += v;
if (scany2 <= maxY)
value[base2] += v;
}

// dy == 0 && dx != 0
base = y*params.width + x;
limDx = radius < maxRx ? -radius : -maxRx;
for (dx = radius < limRx ? -radius : -limRx; dx < 0; dx++) {
v = data - Math.pow(-dx, degree); // attention! power (sqrt(dx^2), degree) == power(dx, degree), but dx < 0 while degree can be float!
if (x + dx >= 0)
value[base + dx] += v;
if (dx >= limDx)
value[base - dx] += v;
}

// dy == dx == 0
value[base] += data;
}
postMessage({'value': value, 'width': params.width, 'height': params.height});
}

/* Uses fact that circle on the screen has 4 axes of symmetry: x = 0, y = 0, y = x, y = -x,
so it computes values for ~1/8 of points and copies them to symmetrical ones
Does not check bounds of the image!
*/
function fastCalc(params, data, value, x, y, radius, radiusSq) {
var width = params.width;
var base = y * width + x;
var deg2 = params.degree / 2;
var radiusSq2 = radiusSq / 2;

var v = 0.0;

var xOffset = 0;
var dx = 0, dy = 0, rx = 0.0, dySq = 0;

var yOffset = base - radius * width;
var yOffset2 = base + radius * width;

for (dy = -radius; dy < 0; dy++, yOffset += width, yOffset2 -= width) {
dySq = Math.pow(dy, 2);
rx = Math.floor(Math.sqrt(radiusSq - dySq));

dx = rx >= -dy ? dy + 1 : -rx;
xOffset = dx * width;
for (; dx < 0; dx++, xOffset += width) {
v = data - Math.pow(Math.pow(dx, 2) + dySq, deg2);

// main and symmetrical over x=0, y = 0;
value[yOffset + dx] += v;
value[yOffset - dx] += v;
value[yOffset2 + dx] += v;
value[yOffset2 - dx] += v;

// symmetrical over y = x, y = -x
value[base + xOffset + dy] += v;
value[base + xOffset - dy] += v;
value[base - xOffset + dy] += v;
value[base - xOffset - dy] += v;
}
//dy == dx
if (dySq <= radiusSq2) {
v = data - Math.pow(2 * dySq, deg2);
value[yOffset + dy] += v;
value[yOffset - dy] += v;
value[yOffset2 + dy] += v;
value[yOffset2 - dy] += v;
}

// dx = 0
v = data - Math.pow(dySq, deg2);
value[yOffset] += v;
value[yOffset2] += v;
value[base + dy] += v;
value[base - dy] += v;
}

// dx == dy == 0
value[base] += data;
}

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