Home > Article > Web Front-end > How Can You Smoothly Connect Multiple Points Using JavaScript?

*Mary-Kate Olsen**Original**2024-11-01 03:22:28**930browse*

In drawing applications, it's essential to be able to connect multiple points smoothly. However, using the native JavaScript line drawing functions (lineTo, quadraticCurveTo, and bezierCurveTo) provides a limited approach, resulting in kinks or disjoint curves. This article explores a method to create smooth curves through a series of points using an approximation technique.

When using separate "curveTo" functions for each pair of points, the resulting curve exhibits discontinuities at the end points. This is because each curve segment is only influenced by its own specific control points.

The proposed solution involves connecting the curves to the midpoints between the subsequent sample points. This creates more continuity at the end points, as the endpoint of one curve becomes a control point for the next.

To implement this approximation, follow these steps:

- Move to the first point using moveTo().
- Iterate through the points, excluding the last two.
- For each point pair (i, i 1), calculate the midpoint (xc, yc).
- Use quadraticCurveTo() to draw a curve from the current point to the midpoint, effectively transitioning to a new curve starting from the midpoint.
- Draw a curve through the last two points using quadraticCurveTo().

Here is a code snippet that demonstrates this approach:

<code class="javascript">const canvas = document.querySelector("canvas"); const ctx = canvas.getContext("2d"); const points = [ { x: 50, y: 50 }, { x: 180, y: 100 }, { x: 75, y: 120 }, { x: 40, y: 40 }, ]; // Move to the first point ctx.moveTo(points[0].x, points[0].y); // Iterate through the remaining points for (var i = 1; i < points.length - 2; i++) { // Calculate the midpoint var xc = (points[i].x + points[i + 1].x) / 2; var yc = (points[i].y + points[i + 1].y) / 2; // Draw a curve from the current point to the midpoint ctx.quadraticCurveTo(points[i].x, points[i].y, xc, yc); } // Curve through the last two points ctx.quadraticCurveTo( points[i].x, points[i].y, points[i + 1].x, points[i + 1].y ); // Stroke the curve ctx.stroke();</code>

This code demonstrates the smooth curve that can be drawn through multiple points using this approximation technique.

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