XProfan

document.addEventListener('keydown', function( e ) { ...

if( g2D ) {// 2D geometry

    x = r * fx[ i ][ j ] * ( j - rs / 2 ) / rs * scX;
    y = h * fh[ i ][ j ] * scY;
    z = 0;

} else  {// 3D geometry

    x =  r * fx[ i ][ j ] * scX * Math.cos( φ( j ) );
    y =  h * fh[ i ][ j ] * scY;
    z = -r * fz[ i ][ j ] * scZ * Math.sin( φ( j ) );

    if ( cover ) {// unroll cover

        z = Math.sqrt( x * x + z * z ) - r * fx[ i ][ 0 ] * scX;
        x = r * fx[ i ][ j ] * scX * φc( j );// center x

    }

}

function RectangleRounded( w, h, r, s ) {// width, height, radiusCorner, smoothness

    const pi2 = Math.PI * 2;
    const n = ( s + 1 ) * 4;// number of segments
    let indices = [];
    let positions = [];
    let uvs = [];
    let qu, sgx, sgy, x, y;
    for ( let j = 1; j < n + 1; j ++ ) indices.push( 0, j, j + 1 );// 0 is center
    indices.push( 0, n, 1 );
    positions.push( 0, 0, 0 );// rectangle center
    uvs.push( 0.5, 0.5 );
    for ( let j = 0; j < n ; j ++ ) contour( j );
    const geometry = new THREE.BufferGeometry( );
    geometry.setIndex( new THREE.BufferAttribute( new Uint32Array( indices ), 1 ) );
    geometry.setAttribute('position', new THREE.BufferAttribute( new Float32Array( positions ), 3 ) );
    geometry.setAttribute('uv', new THREE.BufferAttribute( new Float32Array( uvs ), 2 ) );
    return geometry;

    function contour( j ) {

        qu = Math.trunc( 4 * j / n ) + 1 ;// quadrant  qu: 1..4
        sgx = ( qu === 1 || qu === 4 ? 1 : -1 )// signum left/right
        sgy =  qu < 3 ? 1 : -1;// signum  top / bottom
        x = sgx * ( w / 2 - r ) + r * Math.cos( pi2 * ( j - qu + 1 ) / ( n - 4 ) );// corner center + circle
        y = sgy * ( h / 2 - r ) + r * Math.sin( pi2 * ( j - qu + 1 ) / ( n - 4 ) );
        positions.push( x, y, 0 );
        uvs.push( 0.5 + x / w, 0.5 + y / h );

    }

}