plammertse.github.io/bivector2.html at main · plammertse/plammertse.github.io · GitHub

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<html>
<head>
<title>BiVector in 2D</title>
<script language="JavaScript" src="basiccontext.js"></script>
<script>

var SCL = 1
var base = timesSc( vec2(125,125), SCL );
var vecA = vec2(1,0);
var vecB = vec2(0,-1);
var len = 50 * SCL;

function project( v )
{
    return {
    x: base.x + v.x * len,
    y: base.y + v.y * len };
}

function area(v0,v1)
{
    return v0.x*v1.y - v0.y*v1.x;
}

var selectedThing = 0;

var render = function()
{
	if ( !isActive ) return;
    if ( !context ) return;

    if (mouseIsDown)
    {
        if ( selectedThing == 0 )
        {
            if ( around( mousePos, project(vecA), 8 ) )
                selectedThing = 1;
            else if ( around( mousePos, project(vecB), 8 ) )
                selectedThing = 2;
        }

        if ( selectedThing == 1 )
            vecA = normalize( minus(mousePos,base) );

        if ( selectedThing == 2 )
            vecB = normalize( minus(mousePos,base) );
    }
    else
        selectedThing = 0;

    context.clearRect(0, 0, canvas.width, canvas.height);

    areaBv = -area(vecA,vecB);
    var colorBv = 'rgba(0,102,255,0.8)';
    if ( areaBv < 0 )
        colorBv = 'rgba(0,200,102,0.8)';

    DrawLine( plus(base,vec2(0,-150*SCL)), plus(base,vec2(0,(150+50)*SCL)), 'gray', 1 );
    DrawLine( base, plus(base,vec2(0,-len)), 'gray', 5 );
    WriteText( 'x', plus(base,vec2(90*SCL,-3*SCL)), '15pt '+DefFont, 'gray' );

    DrawLine( plus(base,vec2(-150*SCL,0)), plus(base,vec2(150*SCL,0)), 'gray', 1 );
    DrawLine( base, plus(base,vec2(len,0)), 'gray', 5 );
    WriteText( 'y', plus(base,vec2(3*SCL,-90*SCL)), '15pt '+DefFont, 'gray' );

    DrawDisc( base, 6, 'black' );
    DrawQuad( base, project(vecA), project(plus(vecA,vecB)), project(vecB), colorBv );
    DrawLine( base, project(vecA), 'black', 3 );
    DrawLine( base, project(vecB), 'black', 3 );

    var colorA = '#ff0000'; if ( selectedThing == 1 ) colorA = '#fff';
    DrawDisc( project(vecA), 4, colorA );
    DrawCircle( project(vecA), 8, colorA, 2 );

    var colorB = '#ff0000'; if ( selectedThing == 2 ) colorB = '#fff';
    DrawDisc( project(vecB), 4, colorB );
    DrawCircle( project(vecB), 8, colorB, 2 );

    WriteText( 'a', plus(project(vecA), vec2(0,-10)), '15pt '+DefFont, 'black' )
    WriteText( 'b', plus(project(vecB), vec2(0,-10)), '15pt '+DefFont, 'black' )

    WriteText( "a"+"\u2227"+"b = " + areaBv.toFixed(3) + " x"+"\u2227"+"y", timesSc(vec2(130,280-10),SCL), (11*SCL) + 'pt '+DefFont, colorBv )

	DrawArcSimple( vec3(vecA.x,vecA.y,0), vec3(vecB.x,vecB.y,0), 'white', 1, null, 'white', 1-0.2, 0.2 )

    var basSinY = 250*SCL;
    var basH = 40*SCL;
    DrawLine( vec2(0,basSinY), vec2(250*SCL,basSinY), 'gray', 1 );
    DrawLine( vec2(0,basSinY-basH-20), vec2(250*SCL,basSinY-basH-20), 'gray', 5 );
    context.beginPath();
    context.lineWidth = 1;
    context.strokeStyle = 'yellow';

    for ( var i = 0; i <= 50; ++i )
    {
        var vx = i/50.0 * 2 * Math.PI;
        p = vec2( vx * basH, Math.sin( vx ) * basH + basSinY );
        if (i==0) context.moveTo( p.x, p.y ); else context.lineTo( p.x, p.y );
    }
    context.stroke();

    var dp =  dot( vecA, vecB )
    var as = Math.asin( areaBv );
    var vv = as;
    if ( areaBv > 0 && dp > 0 )
        vv = (Math.PI - as);
    else if ( areaBv < 0 && dp > 0 )
        vv = -as - Math.PI;

    vv = vv + Math.PI;

    DrawLine( vec2(vv*basH,0+basSinY), vec2(vv*basH,areaBv*-basH+basSinY), colorBv, 4 );

}

window.setInterval(render, 16);

</script>
<style>
body { background-color: #ccc; color: white; font-family: arial; font-size: 15px; margin: 0; padding: 0; }
canvas { margin: 0; padding: 0; border: 0px solid black;
/* position: absolute;top: 50%;left: 50%; margin: -300px 0 0 -250px; */
}
</style>
</head>
<body onload="OnLoad()">
<canvas id="myCanvas" width="250" height="300"></canvas>


</div>
</body>
</html>