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point_in_tri_test2.htm
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point_in_tri_test2.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 substract3d(u , v)
{
return {x: u.x - v.x , y:u.y - v.y , z:u.z - v.z};
}
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 dot3d(u , v)
{
return u.x*v.x+u.y*v.y+u.z*v.z;
}
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};
}
function cross(u , v)
{
return { x: u.y * v.z - u.z * v.y ,
y: u.z * v.x - u.x * v.z ,
z: u.x * v.y - u.y * v.x };
}
// devuelve 1 si el punto p1 y el p2 estan del mismo lado del segmento a-b
function mismo_lado(p1,p2, a,b)
{
var rta = 0;
var U = cross(substract3d(b,a), substract3d(p1,a));
var V = cross(substract3d(b,a), substract3d(p2,a));
if(dot3d(U, V) >= 0)
rta = 1;
return rta;
}
function pto_inside(q,p1,p2,p3)
{
var rta = 0
// los paso a 3d con Z = 0
var p = {x:q.x , y:q.y , z:0};
var a = {x:p1.x , y:p1.y , z:0};
var b = {x:p2.x , y:p2.y , z:0};
var c = {x:p3.x , y:p3.y , z:0};
if(mismo_lado(p,a, b,c) && mismo_lado(p,b, a,c) && mismo_lado(p,c, a,b))
rta = 1;
return rta;
}
function draw()
{
if (canvas.getContext)
{
ctx.fillStyle = 'rgba(255,255,255,255)';
ctx.fillRect(0,0,1000,700);
var pto_adentro = pto_inside(P,A,B,C);
// 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();
ctx.font = "12px Arial";
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();
}
</script>
</head>
<body onload="init();">
<canvas id="mycanvas" width="1000" height="700"></canvas>
</body>
</html>