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point_in_tri_test.htm
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point_in_tri_test.htm
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<!DOCTYPE HTML>
<html>
<head>
<script type="text/javascript">
var canvas;
var ctx;
//
// Point in Triangle Test
//
var A = {x:350, y:120};
var B = {x:50, y:530};
var C = {x:720, y:200};
var P = {x:50, y:100};
// Algebra de vectores
// -------------------------------------------------------------
function add(u , v)
{
return {x: u.x + v.x , y:u.y + v.y};
}
function substract(u , v)
{
return {x: u.x - v.x , y:u.y - v.y};
}
function mul(u , k)
{
return {x: u.x*k , y:u.y*k};
}
function dot(u , v)
{
return u.x*v.x+u.y*v.y;
}
function length(u)
{
return Math.sqrt(u.x*u.x + u.y*u.y);
}
function normalize(u)
{
var len = length(u);
u.x /= len;
u.y /= len;
}
function normal(u)
{
return {x: -u.y , y:u.x};
}
// Coordenadas barycentricas
// -------------------------------------------------------------
function barycentric_a( v1x, v1y , v2x , v2y ,v3x , v3y ,px,py)
{
var a;
var A = v1x - v3x;
var B = v2x - v3x;
var C = v3x - px;
var D = v1y - v3y;
var E = v2y - v3y;
var F = v3y - py;
var G = 0;
var H = 0;
var I = 0;
if(A==0 && B==0)
{
var temp = A;
A = D;
D = temp;
temp = B;
B = E;
E = temp;
temp = C;
C = F;
F = temp;
}
a = (B*(F+I) - C*(E+H)) / (A*(E+H) - B*(D+G));
return a;
}
function barycentric_b( v1x, v1y , v2x , v2y ,v3x , v3y ,px,py)
{
var b;
var A = v1x - v3x;
var B = v2x - v3x;
var C = v3x - px;
var D = v1y - v3y;
var E = v2y - v3y;
var F = v3y - py;
var G = 0;
var H = 0;
var I = 0;
if(A==0 && B==0)
{
var temp = A;
A = D;
D = temp;
temp = B;
B = E;
E = temp;
temp = C;
C = F;
F = temp;
}
b = (A*(F+I) - C*(D+G)) / (B*(D+G) - A*(E+H));
return b;
}
function draw()
{
if (canvas.getContext)
{
ctx.fillStyle = 'rgba(255,255,255,255)';
ctx.fillRect(0,0,1000,700);
// computo las coordenadas barycentricas del punto
var a = barycentric_a(A.x,A.y,B.x,B.y,C.x,C.y,P.x,P.y); // gamma
var b = barycentric_b(A.x,A.y,B.x,B.y,C.x,C.y,P.x,P.y); // beta
var g = 1 - b - a; // alpha
var pto_adentro = 0;
if((b >= 0) && (g >= 0) && (b +g <= 1))
{
// punto adentro del triangulo
pto_adentro = 1;
}
// dibujo el triangulo
ctx.fillStyle = pto_adentro ? 'rgba(255,255,0,255)' : 'rgba(255,0,0,255)';
ctx.beginPath();
ctx.moveTo(A.x, A.y);
ctx.lineTo(B.x, B.y);
ctx.lineTo(C.x, C.y);
ctx.lineTo(A.x, A.y);
ctx.closePath();
ctx.fill();
// dibujo los 3 puntos
ctx.fillStyle = 'rgba(120,50,50,255)';
ctx.beginPath();
ctx.arc(A.x, A.y, 5, 0, Math.PI*2,true);
ctx.closePath();
ctx.stroke();
ctx.beginPath();
ctx.arc(B.x, B.y, 5, 0, Math.PI*2,true);
ctx.closePath();
ctx.stroke();
ctx.beginPath();
ctx.arc(C.x, C.y, 5, 0, Math.PI*2,true);
ctx.closePath();
ctx.stroke();
// dibujo el punto
ctx.fillStyle = 'rgba(0,0,0,255)';
ctx.beginPath();
ctx.arc(P.x, P.y, 5, 0, Math.PI*2,true);
ctx.closePath();
ctx.fill();
// dibujo el vector
var dir_b = substract(B,A);
var pto_b = add(A , mul(dir_b , b));
ctx.strokeStyle = 'rgba(255,120,120,255)';
ctx.lineWidth = 4;
ctx.beginPath();
ctx.moveTo(A.x,A.y);
ctx.lineTo(pto_b.x,pto_b.y);
ctx.closePath();
ctx.stroke();
var dir_g = substract(C,A);
var pto_g = add(A , mul(dir_g , g));
ctx.strokeStyle = 'rgba(120,255,120,255)';
ctx.beginPath();
ctx.moveTo(A.x,A.y);
ctx.lineTo(pto_g.x,pto_g.y);
ctx.closePath();
ctx.stroke();
ctx.lineWidth = 1;
if(pto_adentro)
{
ctx.strokeStyle = 'rgba(0,0,0,255)';
ctx.beginPath();
ctx.setLineDash([5,5]);
ctx.moveTo(P.x,P.y);
ctx.lineTo(pto_b.x,pto_b.y);
ctx.closePath();
ctx.stroke();
ctx.beginPath();
ctx.moveTo(P.x,P.y);
ctx.lineTo(pto_g.x,pto_g.y);
ctx.closePath();
ctx.stroke();
ctx.setLineDash([0,0]);
}
ctx.font = "12px Arial";
ctx.fillText("a = "+ a.toString(), 10, 20);
ctx.fillText("b = "+ b.toString(), 10, 40);
ctx.fillText("g = "+ g.toString(), 10, 60);
ctx.fillText("A", A.x, A.y-10);
ctx.fillText("B", B.x, B.y-10);
ctx.fillText("C", C.x, C.y-10);
}
}
function onMouseMove()
{
P.x = window.event.offsetX;
P.y = window.event.offsetY;
draw();
}
function init()
{
canvas = document.getElementById('mycanvas');
ctx = canvas.getContext('2d');
document.addEventListener( "mousemove", onMouseMove, true);
draw();
// 549 351 811 6688
}
</script>
</head>
<body onload="init();">
<canvas id="mycanvas" width="1000" height="700"></canvas>
</body>
</html>