function FluidField(canvas) {
    function addFields(x, s, dt)
    {
        for (var i=0; i<size ; i++ ) x[i] += dt*s[i];
    }

    function set_bnd(b, x)
    {
        if (b===1) {
            for (var i = 1; i <= width; i++) {
                x[i] =  x[i + rowSize];
                x[i + (height+1) *rowSize] = x[i + height * rowSize];
            }

            for (var j = 1; i <= height; i++) {
                x[j * rowSize] = -x[1 + j * rowSize];
                x[(width + 1) + j * rowSize] = -x[width + j * rowSize];
            }
        } else if (b === 2) {
            for (var i = 1; i <= width; i++) {
                x[i] = -x[i + rowSize];
                x[i + (height + 1) * rowSize] = -x[i + height * rowSize];
            }

            for (var j = 1; j <= height; j++) {
                x[j * rowSize] =  x[1 + j * rowSize];
                x[(width + 1) + j * rowSize] =  x[width + j * rowSize];
            }
        } else {
            for (var i = 1; i <= width; i++) {
                x[i] =  x[i + rowSize];
                x[i + (height + 1) * rowSize] = x[i + height * rowSize];
            }

            for (var j = 1; j <= height; j++) {
                x[j * rowSize] =  x[1 + j * rowSize];
                x[(width + 1) + j * rowSize] =  x[width + j * rowSize];
            }
        }
        var maxEdge = (height + 1) * rowSize;
        x[0]                 = 0.5 * (x[1] + x[rowSize]);
        x[maxEdge]           = 0.5 * (x[1 + maxEdge] + x[height * rowSize]);
        x[(width+1)]         = 0.5 * (x[width] + x[(width + 1) + rowSize]);
        x[(width+1)+maxEdge] = 0.5 * (x[width + maxEdge] + x[(width + 1) + height * rowSize]);
    }

    function lin_solve(b, x, x0, a, c)
    {
        if (a === 0 && c === 1) {
            for (var j=1 ; j<=height; j++) {
                var currentRow = j * rowSize;
                ++currentRow;
                for (var i = 0; i < width; i++) {
                    x[currentRow] = x0[currentRow];
                    ++currentRow;
                }
            }
            set_bnd(b, x);
        } else {
            var invC = 1 / c;
            for (var k=0 ; k<iterations; k++) {
                for (var j=1 ; j<=height; j++) {
                    var lastRow = (j - 1) * rowSize;
                    var currentRow = j * rowSize;
                    var nextRow = (j + 1) * rowSize;
                    var lastX = x[currentRow];
                    ++currentRow;
                    for (var i=1; i<=width; i++)
                        lastX = x[currentRow] = (x0[currentRow] + a*(lastX+x[++currentRow]+x[++lastRow]+x[++nextRow])) * invC;
                }
                set_bnd(b, x);
            }
        }
    }

    function diffuse(b, x, x0, dt)
    {
        var a = 0;
        lin_solve(b, x, x0, a, 1 + 4*a);
    }

    function lin_solve2(x, x0, y, y0, a, c)
    {
        if (a === 0 && c === 1) {
            for (var j=1 ; j <= height; j++) {
                var currentRow = j * rowSize;
                ++currentRow;
                for (var i = 0; i < width; i++) {
                    x[currentRow] = x0[currentRow];
                    y[currentRow] = y0[currentRow];
                    ++currentRow;
                }
            }
            set_bnd(1, x);
            set_bnd(2, y);
        } else {
            var invC = 1/c;
            for (var k=0 ; k<iterations; k++) {
                for (var j=1 ; j <= height; j++) {
                    var lastRow = (j - 1) * rowSize;
                    var currentRow = j * rowSize;
                    var nextRow = (j + 1) * rowSize;
                    var lastX = x[currentRow];
                    var lastY = y[currentRow];
                    ++currentRow;
                    for (var i = 1; i <= width; i++) {
                        lastX = x[currentRow] = (x0[currentRow] + a * (lastX + x[currentRow] + x[lastRow] + x[nextRow])) * invC;
                        lastY = y[currentRow] = (y0[currentRow] + a * (lastY + y[++currentRow] + y[++lastRow] + y[++nextRow])) * invC;
                    }
                }
                set_bnd(1, x);
                set_bnd(2, y);
            }
        }
    }

    function diffuse2(x, x0, y, y0, dt)
    {
        var a = 0;
        lin_solve2(x, x0, y, y0, a, 1 + 4 * a);
    }

    function advect(b, d, d0, u, v, dt)
    {
        var Wdt0 = dt * width;
        var Hdt0 = dt * height;
        var Wp5 = width + 0.5;
        var Hp5 = height + 0.5;
        for (var j = 1; j<= height; j++) {
            var pos = j * rowSize;
            for (var i = 1; i <= width; i++) {
                var x = i - Wdt0 * u[++pos];
                var y = j - Hdt0 * v[pos];
                if (x < 0.5)
                    x = 0.5;
                else if (x > Wp5)
                    x = Wp5;
                var i0 = x | 0;
                var i1 = i0 + 1;
                if (y < 0.5)
                    y = 0.5;
                else if (y > Hp5)
                    y = Hp5;
                var j0 = y | 0;
                var j1 = j0 + 1;
                var s1 = x - i0;
                var s0 = 1 - s1;
                var t1 = y - j0;
                var t0 = 1 - t1;
                var row1 = j0 * rowSize;
                var row2 = j1 * rowSize;
                d[pos] = s0 * (t0 * d0[i0 + row1] + t1 * d0[i0 + row2]) + s1 * (t0 * d0[i1 + row1] + t1 * d0[i1 + row2]);
            }
        }
        set_bnd(b, d);
    }

    function project(u, v, p, div)
    {
        var h = -0.5 / Math.sqrt(width * height);
        for (var j = 1 ; j <= height; j++ ) {
            var row = j * rowSize;
            var previousRow = (j - 1) * rowSize;
            var prevValue = row - 1;
            var currentRow = row;
            var nextValue = row + 1;
            var nextRow = (j + 1) * rowSize;
            for (var i = 1; i <= width; i++ ) {
                div[++currentRow] = h * (u[++nextValue] - u[++prevValue] + v[++nextRow] - v[++previousRow]);
                p[currentRow] = 0;
            }
        }
        set_bnd(0, div);
        set_bnd(0, p);

        lin_solve(0, p, div, 1, 4 );
        var wScale = 0.5 * width;
        var hScale = 0.5 * height;
        for (var j = 1; j<= height; j++ ) {
            var prevPos = j * rowSize - 1;
            var currentPos = j * rowSize;
            var nextPos = j * rowSize + 1;
            var prevRow = (j - 1) * rowSize;
            var currentRow = j * rowSize;
            var nextRow = (j + 1) * rowSize;

            for (var i = 1; i<= width; i++) {
                u[++currentPos] -= wScale * (p[++nextPos] - p[++prevPos]);
                v[currentPos]   -= hScale * (p[++nextRow] - p[++prevRow]);
            }
        }
        set_bnd(1, u);
        set_bnd(2, v);
    }

    function dens_step(x, x0, u, v, dt)
    {
        addFields(x, x0, dt);
        diffuse(0, x0, x, dt );
        advect(0, x, x0, u, v, dt );
    }

    function vel_step(u, v, u0, v0, dt)
    {
        addFields(u, u0, dt );
        addFields(v, v0, dt );
        var temp = u0; u0 = u; u = temp;
        var temp = v0; v0 = v; v = temp;
        diffuse2(u,u0,v,v0, dt);
        project(u, v, u0, v0);
        var temp = u0; u0 = u; u = temp;
        var temp = v0; v0 = v; v = temp;
        advect(1, u, u0, u0, v0, dt);
        advect(2, v, v0, u0, v0, dt);
        project(u, v, u0, v0 );
    }
    var uiCallback = function(d,u,v) {};

    function Field(dens, u, v) {
        // Just exposing the fields here rather than using accessors is a measurable win during display (maybe 5%)
        // but makes the code ugly.
        this.setDensity = function(x, y, d) {
             dens[(x + 1) + (y + 1) * rowSize] = d;
        }
        this.getDensity = function(x, y) {
             return dens[(x + 1) + (y + 1) * rowSize];
        }
        this.setVelocity = function(x, y, xv, yv) {
             u[(x + 1) + (y + 1) * rowSize] = xv;
             v[(x + 1) + (y + 1) * rowSize] = yv;
        }
        this.getXVelocity = function(x, y) {
             return u[(x + 1) + (y + 1) * rowSize];
        }
        this.getYVelocity = function(x, y) {
             return v[(x + 1) + (y + 1) * rowSize];
        }
        this.width = function() { return width; }
        this.height = function() { return height; }
    }
    function queryUI(d, u, v)
    {
        for (var i = 0; i < size; i++)
            u[i] = v[i] = d[i] = 0.0;
        uiCallback(new Field(d, u, v));
    }

    this.update = function () {
        queryUI(dens_prev, u_prev, v_prev);
        vel_step(u, v, u_prev, v_prev, dt);
        dens_step(dens, dens_prev, u, v, dt);
        displayFunc(new Field(dens, u, v));
    }
    this.setDisplayFunction = function(func) {
        displayFunc = func;
    }

    this.iterations = function() { return iterations; }
    this.setIterations = function(iters) {
        if (iters > 0 && iters <= 100)
           iterations = iters;
    }
    this.setUICallback = function(callback) {
        uiCallback = callback;
    }
    var iterations = 10;
    var visc = 0.5;
    var dt = 0.1;
    var dens;
    var dens_prev;
    var u;
    var u_prev;
    var v;
    var v_prev;
    var width;
    var height;
    var rowSize;
    var size;
    var displayFunc;
    function reset()
    {
        rowSize = width + 2;
        size = (width+2)*(height+2);
        dens = new Array(size);
        dens_prev = new Array(size);
        u = new Array(size);
        u_prev = new Array(size);
        v = new Array(size);
        v_prev = new Array(size);
        for (var i = 0; i < size; i++)
            dens_prev[i] = u_prev[i] = v_prev[i] = dens[i] = u[i] = v[i] = 0;
    }
    this.reset = reset;
    this.setResolution = function (hRes, wRes)
    {
        var res = wRes * hRes;
        if (res > 0 && res < 1000000 && (wRes != width || hRes != height)) {
            width = wRes;
            height = hRes;
            reset();
            return true;
        }
        return false;
    }
    this.setResolution(64, 64);
}
function FluidField(canvas) {
    function addFields(x, s, dt)
    {
        for (var i=0; i<size ; i++ ) x[i] += dt*s[i];
    }

    function set_bnd(b, x)
    {
        if (b===1) {
            for (var i = 1; i <= width; i++) {
                x[i] =  x[i + rowSize];
                x[i + (height+1) *rowSize] = x[i + height * rowSize];
            }

            for (var j = 1; i <= height; i++) {
                x[j * rowSize] = -x[1 + j * rowSize];
                x[(width + 1) + j * rowSize] = -x[width + j * rowSize];
            }
        } else if (b === 2) {
            for (var i = 1; i <= width; i++) {
                x[i] = -x[i + rowSize];
                x[i + (height + 1) * rowSize] = -x[i + height * rowSize];
            }

            for (var j = 1; j <= height; j++) {
                x[j * rowSize] =  x[1 + j * rowSize];
                x[(width + 1) + j * rowSize] =  x[width + j * rowSize];
            }
        } else {
            for (var i = 1; i <= width; i++) {
                x[i] =  x[i + rowSize];
                x[i + (height + 1) * rowSize] = x[i + height * rowSize];
            }

            for (var j = 1; j <= height; j++) {
                x[j * rowSize] =  x[1 + j * rowSize];
                x[(width + 1) + j * rowSize] =  x[width + j * rowSize];
            }
        }
        var maxEdge = (height + 1) * rowSize;
        x[0]                 = 0.5 * (x[1] + x[rowSize]);
        x[maxEdge]           = 0.5 * (x[1 + maxEdge] + x[height * rowSize]);
        x[(width+1)]         = 0.5 * (x[width] + x[(width + 1) + rowSize]);
        x[(width+1)+maxEdge] = 0.5 * (x[width + maxEdge] + x[(width + 1) + height * rowSize]);
    }

    function lin_solve(b, x, x0, a, c)
    {
        if (a === 0 && c === 1) {
            for (var j=1 ; j<=height; j++) {
                var currentRow = j * rowSize;
                ++currentRow;
                for (var i = 0; i < width; i++) {
                    x[currentRow] = x0[currentRow];
                    ++currentRow;
                }
            }
            set_bnd(b, x);
        } else {
            var invC = 1 / c;
            for (var k=0 ; k<iterations; k++) {
                for (var j=1 ; j<=height; j++) {
                    var lastRow = (j - 1) * rowSize;
                    var currentRow = j * rowSize;
                    var nextRow = (j + 1) * rowSize;
                    var lastX = x[currentRow];
                    ++currentRow;
                    for (var i=1; i<=width; i++)
                        lastX = x[currentRow] = (x0[currentRow] + a*(lastX+x[++currentRow]+x[++lastRow]+x[++nextRow])) * invC;
                }
                set_bnd(b, x);
            }
        }
    }

    function diffuse(b, x, x0, dt)
    {
        var a = 0;
        lin_solve(b, x, x0, a, 1 + 4*a);
    }

    function lin_solve2(x, x0, y, y0, a, c)
    {
        if (a === 0 && c === 1) {
            for (var j=1 ; j <= height; j++) {
                var currentRow = j * rowSize;
                ++currentRow;
                for (var i = 0; i < width; i++) {
                    x[currentRow] = x0[currentRow];
                    y[currentRow] = y0[currentRow];
                    ++currentRow;
                }
            }
            set_bnd(1, x);
            set_bnd(2, y);
        } else {
            var invC = 1/c;
            for (var k=0 ; k<iterations; k++) {
                for (var j=1 ; j <= height; j++) {
                    var lastRow = (j - 1) * rowSize;
                    var currentRow = j * rowSize;
                    var nextRow = (j + 1) * rowSize;
                    var lastX = x[currentRow];
                    var lastY = y[currentRow];
                    ++currentRow;
                    for (var i = 1; i <= width; i++) {
                        lastX = x[currentRow] = (x0[currentRow] + a * (lastX + x[currentRow] + x[lastRow] + x[nextRow])) * invC;
                        lastY = y[currentRow] = (y0[currentRow] + a * (lastY + y[++currentRow] + y[++lastRow] + y[++nextRow])) * invC;
                    }
                }
                set_bnd(1, x);
                set_bnd(2, y);
            }
        }
    }

    function diffuse2(x, x0, y, y0, dt)
    {
        var a = 0;
        lin_solve2(x, x0, y, y0, a, 1 + 4 * a);
    }

    function advect(b, d, d0, u, v, dt)
    {
        var Wdt0 = dt * width;
        var Hdt0 = dt * height;
        var Wp5 = width + 0.5;
        var Hp5 = height + 0.5;
        for (var j = 1; j<= height; j++) {
            var pos = j * rowSize;
            for (var i = 1; i <= width; i++) {
                var x = i - Wdt0 * u[++pos];
                var y = j - Hdt0 * v[pos];
                if (x < 0.5)
                    x = 0.5;
                else if (x > Wp5)
                    x = Wp5;
                var i0 = x | 0;
                var i1 = i0 + 1;
                if (y < 0.5)
                    y = 0.5;
                else if (y > Hp5)
                    y = Hp5;
                var j0 = y | 0;
                var j1 = j0 + 1;
                var s1 = x - i0;
                var s0 = 1 - s1;
                var t1 = y - j0;
                var t0 = 1 - t1;
                var row1 = j0 * rowSize;
                var row2 = j1 * rowSize;
                d[pos] = s0 * (t0 * d0[i0 + row1] + t1 * d0[i0 + row2]) + s1 * (t0 * d0[i1 + row1] + t1 * d0[i1 + row2]);
            }
        }
        set_bnd(b, d);
    }

    function project(u, v, p, div)
    {
        var h = -0.5 / Math.sqrt(width * height);
        for (var j = 1 ; j <= height; j++ ) {
            var row = j * rowSize;
            var previousRow = (j - 1) * rowSize;
            var prevValue = row - 1;
            var currentRow = row;
            var nextValue = row + 1;
            var nextRow = (j + 1) * rowSize;
            for (var i = 1; i <= width; i++ ) {
                div[++currentRow] = h * (u[++nextValue] - u[++prevValue] + v[++nextRow] - v[++previousRow]);
                p[currentRow] = 0;
            }
        }
        set_bnd(0, div);
        set_bnd(0, p);

        lin_solve(0, p, div, 1, 4 );
        var wScale = 0.5 * width;
        var hScale = 0.5 * height;
        for (var j = 1; j<= height; j++ ) {
            var prevPos = j * rowSize - 1;
            var currentPos = j * rowSize;
            var nextPos = j * rowSize + 1;
            var prevRow = (j - 1) * rowSize;
            var currentRow = j * rowSize;
            var nextRow = (j + 1) * rowSize;

            for (var i = 1; i<= width; i++) {
                u[++currentPos] -= wScale * (p[++nextPos] - p[++prevPos]);
                v[currentPos]   -= hScale * (p[++nextRow] - p[++prevRow]);
            }
        }
        set_bnd(1, u);
        set_bnd(2, v);
    }

    function dens_step(x, x0, u, v, dt)
    {
        addFields(x, x0, dt);
        diffuse(0, x0, x, dt );
        advect(0, x, x0, u, v, dt );
    }

    function vel_step(u, v, u0, v0, dt)
    {
        addFields(u, u0, dt );
        addFields(v, v0, dt );
        var temp = u0; u0 = u; u = temp;
        var temp = v0; v0 = v; v = temp;
        diffuse2(u,u0,v,v0, dt);
        project(u, v, u0, v0);
        var temp = u0; u0 = u; u = temp;
        var temp = v0; v0 = v; v = temp;
        advect(1, u, u0, u0, v0, dt);
        advect(2, v, v0, u0, v0, dt);
        project(u, v, u0, v0 );
    }
    var uiCallback = function(d,u,v) {};

    function Field(dens, u, v) {
        
        
        this.setDensity = function(x, y, d) {
             dens[(x + 1) + (y + 1) * rowSize] = d;
        }
        this.getDensity = function(x, y) {
             return dens[(x + 1) + (y + 1) * rowSize];
        }
        this.setVelocity = function(x, y, xv, yv) {
             u[(x + 1) + (y + 1) * rowSize] = xv;
             v[(x + 1) + (y + 1) * rowSize] = yv;
        }
        this.getXVelocity = function(x, y) {
             return u[(x + 1) + (y + 1) * rowSize];
        }
        this.getYVelocity = function(x, y) {
             return v[(x + 1) + (y + 1) * rowSize];
        }
        this.width = function() { return width; }
        this.height = function() { return height; }
    }
    function queryUI(d, u, v)
    {
        for (var i = 0; i < size; i++)
            u[i] = v[i] = d[i] = 0.0;
        uiCallback(new Field(d, u, v));
    }

    this.update = function () {
        queryUI(dens_prev, u_prev, v_prev);
        vel_step(u, v, u_prev, v_prev, dt);
        dens_step(dens, dens_prev, u, v, dt);
        displayFunc(new Field(dens, u, v));
    }
    this.setDisplayFunction = function(func) {
        displayFunc = func;
    }

    this.iterations = function() { return iterations; }
    this.setIterations = function(iters) {
        if (iters > 0 && iters <= 100)
           iterations = iters;
    }
    this.setUICallback = function(callback) {
        uiCallback = callback;
    }
    var iterations = 10;
    var visc = 0.5;
    var dt = 0.1;
    var dens;
    var dens_prev;
    var u;
    var u_prev;
    var v;
    var v_prev;
    var width;
    var height;
    var rowSize;
    var size;
    var displayFunc;
    function reset()
    {
        rowSize = width + 2;
        size = (width+2)*(height+2);
        dens = new Array(size);
        dens_prev = new Array(size);
        u = new Array(size);
        u_prev = new Array(size);
        v = new Array(size);
        v_prev = new Array(size);
        for (var i = 0; i < size; i++)
            dens_prev[i] = u_prev[i] = v_prev[i] = dens[i] = u[i] = v[i] = 0;
    }
    this.reset = reset;
    this.setResolution = function (hRes, wRes)
    {
        var res = wRes * hRes;
        if (res > 0 && res < 1000000 && (wRes != width || hRes != height)) {
            width = wRes;
            height = hRes;
            reset();
            return true;
        }
        return false;
    }
    this.setResolution(64, 64);
}
function FluidField ( canvas ) { function addFields ( x , s , dt ) { for ( var i = 0 ; i < size ; i ++ ) x [ i ] += dt * s [ i ] ; } function set_bnd ( b , x ) { if ( b === 1 ) { for ( var i = 1 ; i <= width ; i ++ ) { x [ i ] = x [ i + rowSize ] ; x [ i + ( height + 1 ) * rowSize ] = x [ i + height * rowSize ] ; } for ( var j = 1 ; i <= height ; i ++ ) { x [ j * rowSize ] = - x [ 1 + j * rowSize ] ; x [ ( width + 1 ) + j * rowSize ] = - x [ width + j * rowSize ] ; } } else if ( b === 2 ) { for ( var i = 1 ; i <= width ; i ++ ) { x [ i ] = - x [ i + rowSize ] ; x [ i + ( height + 1 ) * rowSize ] = - x [ i + height * rowSize ] ; } for ( var j = 1 ; j <= height ; j ++ ) { x [ j * rowSize ] = x [ 1 + j * rowSize ] ; x [ ( width + 1 ) + j * rowSize ] = x [ width + j * rowSize ] ; } } else { for ( var i = 1 ; i <= width ; i ++ ) { x [ i ] = x [ i + rowSize ] ; x [ i + ( height + 1 ) * rowSize ] = x [ i + height * rowSize ] ; } for ( var j = 1 ; j <= height ; j ++ ) { x [ j * rowSize ] = x [ 1 + j * rowSize ] ; x [ ( width + 1 ) + j * rowSize ] = x [ width + j * rowSize ] ; } } var maxEdge = ( height + 1 ) * rowSize ; x [ 0 ] = 0.5 * ( x [ 1 ] + x [ rowSize ] ) ; x [ maxEdge ] = 0.5 * ( x [ 1 + maxEdge ] + x [ height * rowSize ] ) ; x [ ( width + 1 ) ] = 0.5 * ( x [ width ] + x [ ( width + 1 ) + rowSize ] ) ; x [ ( width + 1 ) + maxEdge ] = 0.5 * ( x [ width + maxEdge ] + x [ ( width + 1 ) + height * rowSize ] ) ; } function lin_solve ( b , x , x0 , a , c ) { if ( a === 0 && c === 1 ) { for ( var j = 1 ; j <= height ; j ++ ) { var currentRow = j * rowSize ; ++ currentRow ; for ( var i = 0 ; i < width ; i ++ ) { x [ currentRow ] = x0 [ currentRow ] ; ++ currentRow ; } } set_bnd ( b , x ) ; } else { var invC = 1 / c ; for ( var k = 0 ; k < iterations ; k ++ ) { for ( var j = 1 ; j <= height ; j ++ ) { var lastRow = ( j - 1 ) * rowSize ; var currentRow = j * rowSize ; var nextRow = ( j + 1 ) * rowSize ; var lastX = x [ currentRow ] ; ++ currentRow ; for ( var i = 1 ; i <= width ; i ++ ) lastX = x [ currentRow ] = ( x0 [ currentRow ] + a * ( lastX + x [ ++ currentRow ] + x [ ++ lastRow ] + x [ ++ nextRow ] ) ) * invC ; } set_bnd ( b , x ) ; } } } function diffuse ( b , x , x0 , dt ) { var a = 0 ; lin_solve ( b , x , x0 , a , 1 + 4 * a ) ; } function lin_solve2 ( x , x0 , y , y0 , a , c ) { if ( a === 0 && c === 1 ) { for ( var j = 1 ; j <= height ; j ++ ) { var currentRow = j * rowSize ; ++ currentRow ; for ( var i = 0 ; i < width ; i ++ ) { x [ currentRow ] = x0 [ currentRow ] ; y [ currentRow ] = y0 [ currentRow ] ; ++ currentRow ; } } set_bnd ( 1 , x ) ; set_bnd ( 2 , y ) ; } else { var invC = 1 / c ; for ( var k = 0 ; k < iterations ; k ++ ) { for ( var j = 1 ; j <= height ; j ++ ) { var lastRow = ( j - 1 ) * rowSize ; var currentRow = j * rowSize ; var nextRow = ( j + 1 ) * rowSize ; var lastX = x [ currentRow ] ; var lastY = y [ currentRow ] ; ++ currentRow ; for ( var i = 1 ; i <= width ; i ++ ) { lastX = x [ currentRow ] = ( x0 [ currentRow ] + a * ( lastX + x [ currentRow ] + x [ lastRow ] + x [ nextRow ] ) ) * invC ; lastY = y [ currentRow ] = ( y0 [ currentRow ] + a * ( lastY + y [ ++ currentRow ] + y [ ++ lastRow ] + y [ ++ nextRow ] ) ) * invC ; } } set_bnd ( 1 , x ) ; set_bnd ( 2 , y ) ; } } } function diffuse2 ( x , x0 , y , y0 , dt ) { var a = 0 ; lin_solve2 ( x , x0 , y , y0 , a , 1 + 4 * a ) ; } function advect ( b , d , d0 , u , v , dt ) { var Wdt0 = dt * width ; var Hdt0 = dt * height ; var Wp5 = width + 0.5 ; var Hp5 = height + 0.5 ; for ( var j = 1 ; j <= height ; j ++ ) { var pos = j * rowSize ; for ( var i = 1 ; i <= width ; i ++ ) { var x = i - Wdt0 * u [ ++ pos ] ; var y = j - Hdt0 * v [ pos ] ; if ( x < 0.5 ) x = 0.5 ; else if ( x > Wp5 ) x = Wp5 ; var i0 = x | 0 ; var i1 = i0 + 1 ; if ( y < 0.5 ) y = 0.5 ; else if ( y > Hp5 ) y = Hp5 ; var j0 = y | 0 ; var j1 = j0 + 1 ; var s1 = x - i0 ; var s0 = 1 - s1 ; var t1 = y - j0 ; var t0 = 1 - t1 ; var row1 = j0 * rowSize ; var row2 = j1 * rowSize ; d [ pos ] = s0 * ( t0 * d0 [ i0 + row1 ] + t1 * d0 [ i0 + row2 ] ) + s1 * ( t0 * d0 [ i1 + row1 ] + t1 * d0 [ i1 + row2 ] ) ; } } set_bnd ( b , d ) ; } function project ( u , v , p , div ) { var h = - 0.5 / Math . sqrt ( width * height ) ; for ( var j = 1 ; j <= height ; j ++ ) { var row = j * rowSize ; var previousRow = ( j - 1 ) * rowSize ; var prevValue = row - 1 ; var currentRow = row ; var nextValue = row + 1 ; var nextRow = ( j + 1 ) * rowSize ; for ( var i = 1 ; i <= width ; i ++ ) { div [ ++ currentRow ] = h * ( u [ ++ nextValue ] - u [ ++ prevValue ] + v [ ++ nextRow ] - v [ ++ previousRow ] ) ; p [ currentRow ] = 0 ; } } set_bnd ( 0 , div ) ; set_bnd ( 0 , p ) ; lin_solve ( 0 , p , div , 1 , 4 ) ; var wScale = 0.5 * width ; var hScale = 0.5 * height ; for ( var j = 1 ; j <= height ; j ++ ) { var prevPos = j * rowSize - 1 ; var currentPos = j * rowSize ; var nextPos = j * rowSize + 1 ; var prevRow = ( j - 1 ) * rowSize ; var currentRow = j * rowSize ; var nextRow = ( j + 1 ) * rowSize ; for ( var i = 1 ; i <= width ; i ++ ) { u [ ++ currentPos ] -= wScale * ( p [ ++ nextPos ] - p [ ++ prevPos ] ) ; v [ currentPos ] -= hScale * ( p [ ++ nextRow ] - p [ ++ prevRow ] ) ; } } set_bnd ( 1 , u ) ; set_bnd ( 2 , v ) ; } function dens_step ( x , x0 , u , v , dt ) { addFields ( x , x0 , dt ) ; diffuse ( 0 , x0 , x , dt ) ; advect ( 0 , x , x0 , u , v , dt ) ; } function vel_step ( u , v , u0 , v0 , dt ) { addFields ( u , u0 , dt ) ; addFields ( v , v0 , dt ) ; var temp = u0 ; u0 = u ; u = temp ; var temp = v0 ; v0 = v ; v = temp ; diffuse2 ( u , u0 , v , v0 , dt ) ; project ( u , v , u0 , v0 ) ; var temp = u0 ; u0 = u ; u = temp ; var temp = v0 ; v0 = v ; v = temp ; advect ( 1 , u , u0 , u0 , v0 , dt ) ; advect ( 2 , v , v0 , u0 , v0 , dt ) ; project ( u , v , u0 , v0 ) ; } var uiCallback = function ( d , u , v ) { } ; function Field ( dens , u , v ) { // Just exposing the fields here rather than using accessors is a measurable win during display (maybe 5%) // but makes the code ugly. this . setDensity = function ( x , y , d ) { dens [ ( x + 1 ) + ( y + 1 ) * rowSize ] = d ; } this . getDensity = function ( x , y ) { return dens [ ( x + 1 ) + ( y + 1 ) * rowSize ] ; } this . setVelocity = function ( x , y , xv , yv ) { u [ ( x + 1 ) + ( y + 1 ) * rowSize ] = xv ; v [ ( x + 1 ) + ( y + 1 ) * rowSize ] = yv ; } this . getXVelocity = function ( x , y ) { return u [ ( x + 1 ) + ( y + 1 ) * rowSize ] ; } this . getYVelocity = function ( x , y ) { return v [ ( x + 1 ) + ( y + 1 ) * rowSize ] ; } this . width = function ( ) { return width ; } this . height = function ( ) { return height ; } } function queryUI ( d , u , v ) { for ( var i = 0 ; i < size ; i ++ ) u [ i ] = v [ i ] = d [ i ] = 0.0 ; uiCallback ( new Field ( d , u , v ) ) ; } this . update = function ( ) { queryUI ( dens_prev , u_prev , v_prev ) ; vel_step ( u , v , u_prev , v_prev , dt ) ; dens_step ( dens , dens_prev , u , v , dt ) ; displayFunc ( new Field ( dens , u , v ) ) ; } this . setDisplayFunction = function ( func ) { displayFunc = func ; } this . iterations = function ( ) { return iterations ; } this . setIterations = function ( iters ) { if ( iters > 0 && iters <= 100 ) iterations = iters ; } this . setUICallback = function ( callback ) { uiCallback = callback ; } var iterations = 10 ; var visc = 0.5 ; var dt = 0.1 ; var dens ; var dens_prev ; var u ; var u_prev ; var v ; var v_prev ; var width ; var height ; var rowSize ; var size ; var displayFunc ; function reset ( ) { rowSize = width + 2 ; size = ( width + 2 ) * ( height + 2 ) ; dens = new Array ( size ) ; dens_prev = new Array ( size ) ; u = new Array ( size ) ; u_prev = new Array ( size ) ; v = new Array ( size ) ; v_prev = new Array ( size ) ; for ( var i = 0 ; i < size ; i ++ ) dens_prev [ i ] = u_prev [ i ] = v_prev [ i ] = dens [ i ] = u [ i ] = v [ i ] = 0 ; } this . reset = reset ; this . setResolution = function ( hRes , wRes ) { var res = wRes * hRes ; if ( res > 0 && res < 1000000 && ( wRes != width || hRes != height ) ) { width = wRes ; height = hRes ; reset ( ) ; return true ; } return false ; } this . setResolution ( 64 , 64 ) ; }
Code from Oliver Hunt (http://nerget.com/fluidSim/pressure.js) starts here.
Code from Oliver Hunt ( http : // nerget . com / fluidSim / pressure . js ) starts here .