Unable to read elements from the matrix in loop

For the below code, I'm unable to read the element from the matrix intr in the loop. For example, for the line intr(2,1), I get an error as follows "Index exceeds matrix dimensions.". Can someone help me with this one.

for i = 1:M
      Q1 = vertsTransformed(i,:);
      Q2 = Q1 + vn(i, :);
      line = createLine3d(Q1, Q2);
      [intr, pos, ind] = intersectLineMesh3d(line, modelskin.vertices, modelskin.faces);
      d = intr(2:end, 1:3);
      X = [Q1; intr(2:end, 1:end)];
      intr(2,1)
  end

Thanks!!

Answer 1

[Walter Roberson]

intersectLineMesh3d is going to return an empty matrix if there are no intersection points (or if it is not able to find them.) Or it could return a single point, if that is appropriate. The (2:end,1:3) indexing is not going to be bothered in that case: it would simply return the empty matrix since 2:end would be empty in such a case. But intr(2,1) assumes that there are definitely at least 2 points.

[anusha gorrila]

Hello, In my problem intersectMeshLine3d is always returning at 2 points, and I'm looking for the second point because this point is intersecting the mesh. This is known from pos which is always positive for the second point.

[Guillaume]

If you get "Index exceeds matrix dimensions." at intr(2,1) then you did not get 2 points from intersectLineMesh3d regardless of what your wishes are.