I found code in ‘/three.js/src/geometries/ExtrudeGeometry.js:464’
normal.copy( splineTube.normals[ 0 ] ).multiplyScalar( vert.x ); binormal.copy( splineTube.binormals[ 0 ] ).multiplyScalar( vert.y );
It means that coordinate in extrud are almost only related the direction of normal and binormal. But not the world coordinate.
In some specical cases, such as pull along Axis X or Z.
Value of x or z changed less than y, binormal towards to horizontal.
Value of x or z changed more than y, binormal towards to Vertical.
I think only draw an extrude with a horizontal shape, should we deal it’s coordinate carefully.
In other time, coordinate of shape should not be relate on normal or binormal of spline.