html5-canvas Collisions and Intersections Is an X,Y point inside an arc?
Example
Tests if the [x,y] point is inside a closed arc.
var arc={
cx:150, cy:150,
innerRadius:75, outerRadius:100,
startAngle:0, endAngle:Math.PI
}
function isPointInArc(x,y,arc){
var dx=x-arc.cx;
var dy=y-arc.cy;
var dxy=dx*dx+dy*dy;
var rrOuter=arc.outerRadius*arc.outerRadius;
var rrInner=arc.innerRadius*arc.innerRadius;
if(dxy<rrInner || dxy>rrOuter){return(false);}
var angle=(Math.atan2(dy,dx)+PI2)%PI2;
return(angle>=arc.startAngle && angle<=arc.endAngle);
}
