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/*
* $Id: geometry.js,v 1.5.2.3 2010/04/06 16:46:12 source Exp $
*
* This file is part of the OpenLink Software Ajax Toolkit (OAT) project.
*
* Copyright (C) 2005-2010 OpenLink Software
*
* See LICENSE file for details.
*/
/*
*/
OAT.Geometry = {
sphericalData:{
r:0,
R:0,
cx:0,
cy:0
},
toSpherical:function(x,y) {
var dx = x - OAT.Geometry.sphericalData.cx;
var dy = y - OAT.Geometry.sphericalData.cy;
var dist = dx*dx + dy*dy;
var d = Math.sqrt(dist);
if (d > OAT.Geometry.sphericalData.R) { return false; } /* not within circle - invisible */
var pi2 = Math.PI / 2;
var coef = Math.sin(pi2*d/OAT.Geometry.sphericalData.R);
var new_d = d ? coef * (OAT.Geometry.sphericalData.r/d) : 0
var new_x = OAT.Geometry.sphericalData.cx + dx * new_d;
var new_y = OAT.Geometry.sphericalData.cy + dy * new_d;
return [new_x,new_y];
},
fromSpherical:function(x,y) {
var dx = x - OAT.Geometry.sphericalData.cx;
var dy = y - OAT.Geometry.sphericalData.cy;
var dist = dx*dx + dy*dy;
var d = Math.sqrt(dist);
if (d > OAT.Geometry.sphericalData.r) { return false; }
var pi2 = Math.PI / 2;
var coef = Math.asin(d/OAT.Geometry.sphericalData.r) / pi2;
var new_d = d ? coef * (OAT.Geometry.sphericalData.R/d) : 0
var new_x = OAT.Geometry.sphericalData.cx + dx * new_d;
var new_y = OAT.Geometry.sphericalData.cy + dy * new_d;
return [new_x,new_y]; },
pointVsAbscissa:function(point,abscissa) {
/* returns sign of a point against abscissa: -1 left, 1 right */
var ax = abscissa[0][0];
var ay = abscissa[0][1];
var bx = abscissa[1][0];
var by = abscissa[1][1];
var cx = point[0];
var cy = point[1];
var result = ax*(by - cy) + ay*(cx - bx) + bx*cy - cx*by;
return (result <= 0 ? -1 : 1);
},
pointVsSet:function(point,pointSet,sign) {
/* returns (ordered!) set of indexes from set which have 'sign' against first point */
var result = [];
var startIndex = -1;
for (var i=0;i<pointSet.length;i++) {
var a = pointSet[i];
var b = pointSet[i+1 < pointSet.length ? i+1 : 0];
var s = OAT.Geometry.pointVsAbscissa(point,[a,b]);
if (s == sign) {
if (startIndex == -1) { startIndex = i; }
result.push(i);
} else {
startIndex = -1;
}
}
if (result.length && startIndex != -1) {
while (result[0] != startIndex) {
var first = result.shift();
result.push(first);
}
}
return result;
},
enlargeConvexPolygon:function(point,polygon) {
/* tries to add a new point to a polygonal CW oriented border */
var subset = OAT.Geometry.pointVsSet(point,polygon,1);
if (!subset.length) { return false; } /* point lies inside */
if (subset.length == 1) {
/* easy, just insert the point -> enlargement */
var index = subset[0];
polygon.splice(index+1,0,point);
} else {
/* harder, insert the point and delete others */
/* typical contents of subset: [0,1,2,3] / [2,3] / [4,5,0] */
var toDelete = [];
for (var i=1;i<subset.length;i++) { toDelete.push(polygon[subset[i]]); }
polygon.splice(subset[0]+1,0,point);
for (var i=0;i<toDelete.length;i++) {
var index = polygon.indexOf(toDelete[i]);
polygon.splice(index,1);
}
}
return polygon;
},
createConvexPolygon:function(pointSet) {
if (pointSet.length < 3) { return false; }
var polygon = [];
polygon.push(pointSet[0]);
polygon.push(pointSet[1]);
var sign = OAT.Geometry.pointVsAbscissa(pointSet[2],polygon);
if (sign == -1) { polygon.push(pointSet[2]); } else { polygon.splice(1,0,pointSet[2]); }
/* we now have CW oriented triangle */
for (var i=3;i<pointSet.length;i++) {
OAT.Geometry.enlargeConvexPolygon(pointSet[i],polygon);
}
return polygon;
},
findCOG:function(polygon) {
/* find center of gravity for CW oriented polygon */
var last_x, last_y; /* prvni/posledni bod */
var p_x, p_y; /* predchozi bod */
var t_x = 0; /* teziste x */
var t_y = 0; /* teziste y */
var t_m = 0; /* suma jmenovatele */
for (var i=0;i<polygon.length;i++) {
var a = polygon[i];
var b = polygon[i+1 < polygon.length ? i+1 : 0];
var m = b[0] * a[1] - a[0] * b[1];
t_x += (b[0] + a[0]) * m;
t_y += (b[1] + a[1]) * m;
t_m += m;
}
t_x /= t_m * 3.0;
t_y /= t_m * 3.0;
return [t_x,t_y];
},
movePoint:function(point,center,distance) { /* shifts point in direction from center by distance */
var dx = point[0]-center[0];
var dy = point[1]-center[1];
var a = Math.atan2(dy,dx);
var x = point[0] + distance * Math.cos(a);
var y = point[1] + distance * Math.sin(a);
return [x,y];
},
middleVector:function(center,a,b) { /* for center point C and two vectors returns vector which halves angle ACB */
var pa = [];
var pb = [];
pa.push(center[0]+a[0]);
pa.push(center[1]+a[1]);
pb.push(center[0]+b[0]);
pb.push(center[1]+b[1]);
var v = [];
v.push(pb[0]-pa[0]);
v.push(pb[1]-pa[1]);
return [v[1],-v[0]];
},
distance:function(a,b) {
var dx = b[0]-a[0];
var dy = b[1]-a[1];
return Math.sqrt(dx*dx+dy*dy);
}
}
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