threejs/examples/js/geometries/RoundedBoxGeometry.js

( function () {

	const _tempNormal = new THREE.Vector3();
	function getUv( faceDirVector, normal, uvAxis, projectionAxis, radius, sideLength ) {

		const totArcLength = 2 * Math.PI * radius / 4;

		// length of the planes between the arcs on each axis
		const centerLength = Math.max( sideLength - 2 * radius, 0 );
		const halfArc = Math.PI / 4;

		// Get the vector projected onto the Y plane
		_tempNormal.copy( normal );
		_tempNormal[ projectionAxis ] = 0;
		_tempNormal.normalize();

		// total amount of UV space alloted to a single arc
		const arcUvRatio = 0.5 * totArcLength / ( totArcLength + centerLength );

		// the distance along one arc the point is at
		const arcAngleRatio = 1.0 - _tempNormal.angleTo( faceDirVector ) / halfArc;
		if ( Math.sign( _tempNormal[ uvAxis ] ) === 1 ) {

			return arcAngleRatio * arcUvRatio;

		} else {

			// total amount of UV space alloted to the plane between the arcs
			const lenUv = centerLength / ( totArcLength + centerLength );
			return lenUv + arcUvRatio + arcUvRatio * ( 1.0 - arcAngleRatio );

		}

	}

	class RoundedBoxGeometry extends THREE.BoxGeometry {

		constructor( width = 1, height = 1, depth = 1, segments = 2, radius = 0.1 ) {

			// ensure segments is odd so we have a plane connecting the rounded corners
			segments = segments * 2 + 1;

			// ensure radius isn't bigger than shortest side
			radius = Math.min( width / 2, height / 2, depth / 2, radius );
			super( 1, 1, 1, segments, segments, segments );

			// if we just have one segment we're the same as a regular box
			if ( segments === 1 ) return;
			const geometry2 = this.toNonIndexed();
			this.index = null;
			this.attributes.position = geometry2.attributes.position;
			this.attributes.normal = geometry2.attributes.normal;
			this.attributes.uv = geometry2.attributes.uv;

			//

			const position = new THREE.Vector3();
			const normal = new THREE.Vector3();
			const box = new THREE.Vector3( width, height, depth ).divideScalar( 2 ).subScalar( radius );
			const positions = this.attributes.position.array;
			const normals = this.attributes.normal.array;
			const uvs = this.attributes.uv.array;
			const faceTris = positions.length / 6;
			const faceDirVector = new THREE.Vector3();
			const halfSegmentSize = 0.5 / segments;
			for ( let i = 0, j = 0; i < positions.length; i += 3, j += 2 ) {

				position.fromArray( positions, i );
				normal.copy( position );
				normal.x -= Math.sign( normal.x ) * halfSegmentSize;
				normal.y -= Math.sign( normal.y ) * halfSegmentSize;
				normal.z -= Math.sign( normal.z ) * halfSegmentSize;
				normal.normalize();
				positions[ i + 0 ] = box.x * Math.sign( position.x ) + normal.x * radius;
				positions[ i + 1 ] = box.y * Math.sign( position.y ) + normal.y * radius;
				positions[ i + 2 ] = box.z * Math.sign( position.z ) + normal.z * radius;
				normals[ i + 0 ] = normal.x;
				normals[ i + 1 ] = normal.y;
				normals[ i + 2 ] = normal.z;
				const side = Math.floor( i / faceTris );
				switch ( side ) {

					case 0:
						// right

						// generate UVs along Z then Y
						faceDirVector.set( 1, 0, 0 );
						uvs[ j + 0 ] = getUv( faceDirVector, normal, 'z', 'y', radius, depth );
						uvs[ j + 1 ] = 1.0 - getUv( faceDirVector, normal, 'y', 'z', radius, height );
						break;
					case 1:
						// left

						// generate UVs along Z then Y
						faceDirVector.set( - 1, 0, 0 );
						uvs[ j + 0 ] = 1.0 - getUv( faceDirVector, normal, 'z', 'y', radius, depth );
						uvs[ j + 1 ] = 1.0 - getUv( faceDirVector, normal, 'y', 'z', radius, height );
						break;
					case 2:
						// top

						// generate UVs along X then Z
						faceDirVector.set( 0, 1, 0 );
						uvs[ j + 0 ] = 1.0 - getUv( faceDirVector, normal, 'x', 'z', radius, width );
						uvs[ j + 1 ] = getUv( faceDirVector, normal, 'z', 'x', radius, depth );
						break;
					case 3:
						// bottom

						// generate UVs along X then Z
						faceDirVector.set( 0, - 1, 0 );
						uvs[ j + 0 ] = 1.0 - getUv( faceDirVector, normal, 'x', 'z', radius, width );
						uvs[ j + 1 ] = 1.0 - getUv( faceDirVector, normal, 'z', 'x', radius, depth );
						break;
					case 4:
						// front

						// generate UVs along X then Y
						faceDirVector.set( 0, 0, 1 );
						uvs[ j + 0 ] = 1.0 - getUv( faceDirVector, normal, 'x', 'y', radius, width );
						uvs[ j + 1 ] = 1.0 - getUv( faceDirVector, normal, 'y', 'x', radius, height );
						break;
					case 5:
						// back

						// generate UVs along X then Y
						faceDirVector.set( 0, 0, - 1 );
						uvs[ j + 0 ] = getUv( faceDirVector, normal, 'x', 'y', radius, width );
						uvs[ j + 1 ] = 1.0 - getUv( faceDirVector, normal, 'y', 'x', radius, height );
						break;

				}

			}

		}

	}

	THREE.RoundedBoxGeometry = RoundedBoxGeometry;

} )();