code: public float getTangentX(int vertex) {
          if (!hasTangentsAndBitangents()) {
              throw new IllegalStateException("mesh has no tangents");
          }
          
          checkVertexIndexBounds(vertex);
          
          return m_tangents.getFloat(vertex * 3 * SIZEOF_FLOAT);
      }
docs: Returns the x-coordinate of a vertex tangent.
  
  @param vertex the vertex index
  @return the x coordinate