Using Three.js, (although I believe this is more math related) I have a set of 2D points that can create a 2D geometry. such as square, rectangle, pentagon, or custom 2D shape. Based of the original 2D shape, I would like to create a method to offset the points inward or outward uniformly in such a way like the attached image.
I don't know if there is a simple way to offset/grow/shrink all the points (vector3) uniformly on the 2D shape inward or outward. And if so, it'll be cool if I can offset the points by X distance? Kinda of like saying offset the points on the 2D shape outward or inward by X distance.
And no, I'm not referring to scaling from a center point. While scaling may work for symmetrical shapes, it won't work when it comes to non-symmetrical shapes.
Thanks in advance.
You can read that forum thread.
I've made some changes with ProfiledContourGeometry
and got OffsetContour
, so I leave it here, just in case, what if it helps :)
function OffsetContour(offset, contour) {
let result = [];
offset = new THREE.BufferAttribute(new Float32Array([offset, 0, 0]), 3);
console.log("offset", offset);
for (let i = 0; i < contour.length; i++) {
let v1 = new THREE.Vector2().subVectors(contour[i - 1 < 0 ? contour.length - 1 : i - 1], contour[i]);
let v2 = new THREE.Vector2().subVectors(contour[i + 1 == contour.length ? 0 : i + 1], contour[i]);
let angle = v2.angle() - v1.angle();
let halfAngle = angle * 0.5;
let hA = halfAngle;
let tA = v2.angle() + Math.PI * 0.5;
let shift = Math.tan(hA - Math.PI * 0.5);
let shiftMatrix = new THREE.Matrix4().set(
1, 0, 0, 0,
-shift, 1, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
);
let tempAngle = tA;
let rotationMatrix = new THREE.Matrix4().set(
Math.cos(tempAngle), -Math.sin(tempAngle), 0, 0,
Math.sin(tempAngle), Math.cos(tempAngle), 0, 0,
0, 0, 1, 0,
0, 0, 0, 1
);
let translationMatrix = new THREE.Matrix4().set(
1, 0, 0, contour[i].x,
0, 1, 0, contour[i].y,
0, 0, 1, 0,
0, 0, 0, 1,
);
let cloneOffset = offset.clone();
console.log("cloneOffset", cloneOffset);
shiftMatrix.applyToBufferAttribute(cloneOffset);
rotationMatrix.applyToBufferAttribute(cloneOffset);
translationMatrix.applyToBufferAttribute(cloneOffset);
result.push(new THREE.Vector2(cloneOffset.getX(0), cloneOffset.getY(0)));
}
return result;
}
Feel free to modify it :)