project: function(p,axis,i){
i = i || vec.make();
i[0] = Infinity;
i[1] = -Infinity;
for(var j=0; j < p.length; j++){
var dot = vec.dot(axis,p.vertices[j])
if( dot < i[0] ){
i[0] = dot;
}
if( dot > i[1] ){
i[1] = dot;
}
}
return i;
}
collides: function(a,b,v,o){
var res = o || {};
res.intersect = true;
res.willIntersect = true;
res.minTranslationVector = null;
res.nearestEdge = null;
v = v || vec.make()
var minIntervalDistance = Infinity;
var translationAxis = vec.make();
var nearestEdge = vec.make();
var axis = vec.make()
var iA = vec.make();
var iB = vec.make();
var cA, cB, cD;
// loop through all edges of both polygons
for(var i=0; i < (a.length+b.length); i++){
var e = i < a.length ? i : i-a.length
var edge = i < a.length ? a.edges[e] : b.edges[e]
vec.perp(edge,axis)
vec.norm(axis,axis)
poly.project(a,axis,iA)
poly.project(b,axis,iB)
// are they currently intersecting?
var iD = intervalDistance(iA,iB);
if( iD >= 0 ){
res.intersect = false;
}
// will they intersect?
var vProj = vec.dot(axis,v);
if( vProj < 0 ){
iA[0] += vProj;
} else {
iA[1] += vProj;
}
iD = intervalDistance(iA,iB);
if( iD >= 0 ){
res.willIntersect = false;
}
// find out if it's the closest one
iD = Math.abs(iD);
if( iD < minIntervalDistance ){
minIntervalDistance = iD;
vec.copy(edge, nearestEdge);
vec.copy(axis, translationAxis);
cA = cA || poly.centroid(a)
cB = cB || poly.centroid(b)
cD = vec.sub(cA, cB, cD);
if( vec.dot(cD, translationAxis) < 0 ){
vec.neg(translationAxis,translationAxis)
}
}
// no intersection is and won't happen
if( !res.intersect && !res.willIntersect ){
break;
}
}
// the minimum translation vector can
// be used to push the polygons apart
if( res.willIntersect ){
translationAxis[0] *= minIntervalDistance;
translationAxis[1] *= minIntervalDistance;
res.minTranslationVector = translationAxis;
res.nearestEdge = nearestEdge;
} else {
vec.free(translationAxis)
vec.free(nearestEdge)
}
vec.free(iA)
vec.free(iB)
vec.free(cA)
vec.free(cB)
vec.free(cD)
vec.free(axis)
// free `v` if it wasn't passed in as
// an argument
if( !arguments[2] ){
vec.free(v);
}
return res;
},