Question

Using this 2d bin-packing algorithm (EDIT: Fixed demo) which is a variation of this how can I get the final bin width and height of each bin?

My demo code follows:

 var blocks = [
    {w: 1000, h: 800},
    {w: 500, h: 700},
    {w: 500, h: 700},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 500, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350},
    {w: 250, h: 350}
];

var sheets = [];

while(blocks.length) {
    var packer = new GrowingPacker(1000,800);
    packer.fit(blocks);

    sheet = [];
    for (var i=blocks.length-1; i>=0; i--) {
        if (blocks[i].fit !== undefined && blocks[i].fit !== null) {
            //console.log(blocks[i].fit);
            sheet.unshift(blocks[i]);
            blocks.splice(i,1);
        }
    }
    //console.log(sheet[sheet.length-1].fit.y + sheet[sheet.length-1].h);
    //console.log(sheet);
    sheets.push(sheet);
}


for(var i=0; i<sheets.length; i++) {
    var sheet = sheets[i];
    var sheetWidth = sheet[sheet.length-1].w + sheet[sheet.length-1].fit.x;
    var sheetHeight = sheet[sheet.length-1].h + sheet[sheet.length-1].fit.y;

    for(var j=0; j<sheet.length; j++) {
        console.log("SHEET #" + i + " - W: " + sheetWidth + " H: " + sheetHeight + " BLOCK #" + j + " - W: " + sheet[j].w + " H: " + sheet[j].h + " X: " + sheet[j].fit.x + " Y: " + sheet[j].fit.y);
    }
}

The original algorithm only deals with a single, ever-expanding bin so I modified it to take a max width and height. Then I run through the array of blocks, call the packer, push fit blocks to a new array and unset them from ‘blocks’ until ‘blocks’ is empty. Whether that was the best approach is the subject of another question.

Anyway, I’ve tried modifying growNode like so:

growNode: function(w, h) {
    var canGrowRight  = (w <= this.root.w && this.root.w + w <= maxW);
    var canGrowDown = (h <= this.root.h && this.root.h + h <= maxH);

    if (canGrowRight) {
        this.sheetW = this.root.w + w; //<--------------added
        return this.growRight(w, h);
    }
    else if (canGrowDown) {
        this.sheetH = this.root.h + h; //<--------------added
        return this.growDown(w, h);
    }
    else

        return null; // need to ensure sensible root starting size to avoid this happening
},

which works for every sheet but the first one. I tried to add these lines in a few other methods as well with no success. I also tried to get the sheet size from the last block in the sheet’s width + x but that only works if the sheet is full.

My question again is how can I get the final sheet size for each sheet?

Answer 1

I eventually figured it out. I added two lines to findNode()

findNode: function(root, w, h) {
    if (root.used) {
        return this.findNode(root.right, w, h) || this.findNode(root.down, w, h);
    }
    else if ((w <= root.w && w <= this.maxW) && (h <= root.h && w <= this.maxW)) {
        this.binWidth = this.root.w <= this.maxW ? this.root.w : this.maxW;
        this.binHeight = this.root.h <= this.maxH ? this.root.h : this.maxH;
        return root;
    }
    else {
        return null;
    }
},

Here is the jsfiddle if you want to play with it. I recommend trying something like this for the input:

100x80
50x70
50x35x2
25x35x4