public void setArrowExtent(Vector3f extent) {
        float len = extent.length();
//        Vector3f dir = extent.normalize();

        tempQuat.lookAt(extent, Vector3f.UNIT_Y);
        tempQuat.normalizeLocal();

        VertexBuffer pvb = getBuffer(Type.Position);
        FloatBuffer buffer = (FloatBuffer)pvb.getData(); 
        buffer.rewind();
        for (int i = 0; i < positions.length; i += 3) {
            Vector3f vec = tempVec.set(positions[i],
                    positions[i + 1],
                    positions[i + 2]);
            vec.multLocal(len);
            tempQuat.mult(vec, vec);

            buffer.put(vec.x);
            buffer.put(vec.y);
            buffer.put(vec.z);
        }
        
        pvb.updateData(buffer);

        updateBound();
        updateCounts();
    }
Sets the arrow's extent.
This will modify the buffers on the mesh.

@param extent the arrow's extent.
jme3-core/src/main/java/com/jme3/scene/debug/Arrow.java