code: public float getBitangentY(int vertex) {
          if (!hasTangentsAndBitangents()) {
              throw new IllegalStateException("mesh has no bitangents");
          }
          
          checkVertexIndexBounds(vertex);
          
          return m_bitangents.getFloat((vertex * 3 + 1) * SIZEOF_FLOAT);
      }
docs: Returns the y-coordinate of a vertex tangent.
  
  @param vertex the vertex index
  @return the y coordinate