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p5.js | curvePoint() Function
• Last Updated : 20 May, 2020

The curvePoint() function in p5.js is used to evaluate the coordinates of a curve at the given point. It takes in the coordinates of the curve for a particular axis and finds the coordinate of the curve at point “t”, which can be specified as a parameter.

The complete position of a point in the curve can be found out by finding using the function once on the x-coordinates and once on the y-coordinates of the curve and then using them together.

Syntax:

`curvePoint( a, b, c, d, t )`

Parameters: This function accepts five parameters as mentioned above and described below:

• a: It is a number that specifies the first point of the curve.
• b: It is a number that specifies the first control point of the curve.
• c: It is a number that specifies the second control point of the curve.
• d: It is a number that specifies the second point of the curve.
• t: It is a number between 0 and 1, which is used as the position between the beginning and ending of the curve coordinates.

Return Value: It returns a number which specifies the curve value at the given position.

The examples below illustrates the curvePoint() function in p5.js:

Example 1:

 `function` `setup() {``  ``createCanvas(600, 300);``  ``textSize(18);`` ` `  ``curvePointLocationSlider = createSlider(0, 1, 0, 0.1);``  ``curvePointLocationSlider.position(20, 40);``}`` ` `function` `draw() {``  ``background(``"green"``);``  ``fill(``"black"``);``  ``text(``    ``"Move the slider to change the location of the displayed curve point"``,``    ``10, 20``  ``);`` ` `  ``// Get the required location of curve``  ``curvePointLocationValue = curvePointLocationSlider.value();`` ` `  ``let p1 = { x: 50, y: 250 };``  ``let p2 = { x: 140, y: 150 };``  ``let p3 = { x: 400, y: 150 };``  ``let p4 = { x: 350, y: 250 };`` ` `  ``// Draw curve using curveVertex()``  ``beginShape();``  ``curveVertex(p1.x, p1.y);``  ``curveVertex(p2.x, p2.y);``  ``curveVertex(p3.x, p3.y);``  ``curveVertex(p4.x, p4.y);``  ``endShape();`` ` `  ``// Find the X and Y coordinate using the curvePoint() function``  ``let pointX = curvePoint(p1.x, p2.x, p3.x, p4.x, curvePointLocationValue);``  ``let pointY = curvePoint(p1.y, p2.y, p3.y, p4.y, curvePointLocationValue);``  ``fill(``"orange"``);`` ` `  ``// Display a circle at that point``  ``circle(pointX, pointY, 10);``}`

Output: Example 2:

 `function` `setup() {``  ``createCanvas(600, 300);``  ``textSize(18);`` ` `  ``maxPointsSlider = createSlider(2, 20, 10, 1);``  ``maxPointsSlider.position(20, 40);``}`` ` `function` `draw() {``  ``background(``"green"``);``  ``fill(``"black"``);``  ``text(``"Move the slider to change the number of intermediate points"``, 10, 20);`` ` `  ``// Get the required location of curve``  ``maxPoints = maxPointsSlider.value();`` ` `  ``let p1 = { x: 50, y: 250 };``  ``let p2 = { x: 100, y: 150 };``  ``let p3 = { x: 500, y: 150 };``  ``let p4 = { x: 350, y: 250 };`` ` `  ``// Draw curve using curveVertex()``  ``beginShape();``  ``curveVertex(p1.x, p1.y);``  ``curveVertex(p2.x, p2.y);``  ``curveVertex(p3.x, p3.y);``  ``curveVertex(p4.x, p4.y);``  ``endShape();`` ` `  ``for` `(let i = 0; i <= maxPoints; i++) {``    ``// Calculate step using the maximum number of points``    ``let step = i / maxPoints;`` ` `    ``// Find the X and Y coordinate using the curvePoint() function``    ``let pointX = curvePoint(p1.x, p2.x, p3.x, p4.x, step);``    ``let pointY = curvePoint(p1.y, p2.y, p3.y, p4.y, step);``    ``fill(``"orange"``);`` ` `    ``// Display a circle at that point``    ``circle(pointX, pointY, 10);``  ``}``}`

Output: Online editor: https://editor.p5js.org/

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