# Find point on curve

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This example finds a point on a bezier or cubic curve at `position` where `position` is he unit distance on the curve 0 <= `position` <= 1. The position is clamped to the range thus if values < 0 or > 1 are passed they will be set 0,1 respectively.

Pass the function 6 coordinates for quadratic bezier or 8 for cubic.

The last optional argument is the returned vector (point). If not given it will be created.

## Example usage

``````var p1 = {x : 10 , y : 100};
var p2 = {x : 100, y : 200};
var p3 = {x : 200, y : 0};
var p4 = {x : 300, y : 100};
var point = {x : null, y : null};

// for cubic beziers
point = getPointOnCurve(0.5, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, point);
// or No need to set point as it is a referance and will be set
getPointOnCurve(0.5, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y, point);
// or to create a new point
var point1 = getPointOnCurve(0.5, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y);

point = getPointOnCurve(0.5, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, null, null, point);
// or No need to set point as it is a referance and will be set
getPointOnCurve(0.5, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, null, null, point);
// or to create a new point
var point1 = getPointOnCurve(0.5, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);``````

## The function

getPointOnCurve = function(position, x1, y1, x2, y2, x3, y3, [x4, y4], [vec])

Note: Arguments inside [x4, y4] are optional.
Note: x4,y4 if null, or undefined means that the curve is a quadratic bezier. vec is optional and will hold the returned point if supplied. If not it will be created.
``````var getPointOnCurve = function(position, x1, y1, x2, y2, x3, y3, x4, y4, vec){
if(vec === undefined){
vec = {};
}

if(x4 === undefined || x4 === null){
x4 = x3;
y4 = y3;
}

if(position <= 0){
vec.x = x1;
vec.y = y1;
return vec;
}
if(position >= 1){
vec.x = x4;
vec.y = y4;
return vec;
}
c = position;
x1 += (x2 - x1) * c;
y1 += (y2 - y1) * c;
x2 += (x3 - x2) * c;
y2 += (y3 - y2) * c;
vec.x = x1 + (x2 - x1) * c;
vec.y = y1 + (y2 - y1) * c;
return vec;
}
x1 += (x2 - x1) * c;
y1 += (y2 - y1) * c;
x2 += (x3 - x2) * c;
y2 += (y3 - y2) * c;
x3 += (x4 - x3) * c;
y3 += (y4 - y3) * c;
x1 += (x2 - x1) * c;
y1 += (y2 - y1) * c;
x2 += (x3 - x2) * c;
y2 += (y3 - y2) * c;
vec.x = x1 + (x2 - x1) * c;
vec.y = y1 + (y2 - y1) * c;
return vec;
}``````