code: function getParentWorldMatrix (jointName, keyframe, jointParents, keyframeJointMatrices) {
    // child -> parent -> parent -> ...
    var jointMatrixTree = foo(jointName, keyframe, jointParents, keyframeJointMatrices)
    // TODO: Revisit this. Thrown in to pass tests. Maybe just return `jointMatrix`
    // when there aren't any parent matrices to factor in
    var worldMatrix = [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1]
    jointMatrixTree.forEach(function (jointMatrix) {
      // TODO: Still not sure why we multiply in this order
      mat4Multiply(worldMatrix, worldMatrix, jointMatrix)
    })
    return worldMatrix
  }
docs: TODO: Refactor. Depth first traversal might make all of this less hacky