如何开发网页版CAD的样条曲线功能

CAD梦想画图 · 发表于 2023-5-26 11:39:35

以下是网页CAD中使用 JavaScript 和 HTML5 Canvas 绘制样条曲线的示例代码：

HTML 代码：

<!DOCTYPE html>
<html>
<head>
<title>Spline Curve</title>
<meta charset="UTF-8">
<style type="text/css">
canvas {
border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="canvas" width="800" height="500"></canvas>
<script src="spline.js"></script>
<script>
// 绘制样条曲线
var canvas = document.getElementById('canvas');
if (canvas.getContext) {
var ctx = canvas.getContext('2d');
ctx.fillStyle = 'white';
ctx.fillRect(0, 0, canvas.width, canvas.height);
var points = [
{ x: 50, y: 100 },
{ x: 200, y: 150 },
{ x: 300, y: 250 },
{ x: 400, y: 200 },
{ x: 500, y: 300 }
];
var tension = 0.5;
var segments = 50;
var splinePoints = getSplinePoints(points, tension, segments);
drawCurve(ctx, splinePoints);
}
</script>
</body>
</html>
JavaScript 代码（spline.js）：
// 计算样条曲线上的点
function getSplinePoints(points, tension, segments) {
if (points.length < 2) return [];
// 初始化矩阵
var m = [];
for (var i = 0; i < points.length; i++) {
m[i] = [1, points[i].x, points[i].x * points[i].x, points[i].x * points[i].x * points[i].x];
}
// 计算常数向量
var b = [];
for (var i = 0; i < points.length; i++) {
b[i] = [points[i].y];
}
// 计算系数矩阵
var mt = math.transpose(m);
var a = math.multiply(mt, m);
var ai = math.inv(a);
var x = math.multiply(ai, mt);
x = math.multiply(x, b);
// 计算曲线上的点
var curve = [];
for (var i = 0; i < (points.length - 1); i++) {
for (var j = 0; j < segments; j++) {
var t = j / segments;
var t2 = t * t;
var t3 = t2 * t;
var h00 = 2 * t3 - 3 * t2 + 1;
var h01 = -2 * t3 + 3 * t2;
var h10 = t3 - 2 * t2 + t;
var h11 = t3 - t2;
var px = h00 * points[i].x + h01 * points[i + 1].x + h10 * tension * (points[i + 1].x - points[i].x) + h11 * tension * (points[i + 2].x - points[i + 1].x);
var py = h00 * x[i][0] + h01 * x[i + 1][0] + h10 * tension * (x[i + 1][0] - x[i][0]) + h11 * tension * (x[i + 2][0] - x[i + 1][0]);
curve.push({ x: px, y: py });
}
}
return curve;
}
// 绘制曲线
function drawCurve(ctx, points) {
ctx.lineWidth = 2;
ctx.strokeStyle = 'black';
ctx.beginPath();
ctx.moveTo(points[0].x, points[0].y);
for (var i = 1; i < points.length; i++) {
ctx.lineTo(points[i].x, points[i].y);
}
ctx.stroke();
}<span style="font-family: 宋体; font-size: 10.5pt; background-color: rgb(255, 255, 255);"> </span>

复制代码

使用这个代码，你可以在网页中绘制出指定点的样条曲线。代码中的 points 数组包含要绘制曲线的点，tension 参数控制曲线的平滑度，segments 参数控制曲线的精细度，以上是在线CAD中样条曲线的开发思路，有其他问题可以到梦想CAD控件官网查看云图产品文档。

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[软件与安装] 如何开发网页版CAD的样条曲线功能

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