Hello everyone,

I am going to reply to a question Lara submitted in this forum, since it contains information that might be interesting for other users:
I think we are talking the same thing, but with two different approaches. I understand your point of view, but let me explain mine a little better.
Lets say we have the following 2 structures (figure 1), from which green is meanA and semitransparent red is meanB, and I want to see how meanB changes with respect to meanA (distances computed from A to B, so order in MeshMath is MeshMath meanB -subtract meanA).

Figure 1: https://drive.google.com/open?id=0B06eo8efbhotZTl4STBzeWRObHc

After we do -subtract operation in MeshMath in that orders our vectors have the following form (figure 2):

Figure 2: https://drive.google.com/open?id=0B06eo8efbhotRklJSVZtS25ab2s

That makes sense, right? our vectors will be pointing from meanA to meanB. They are a 3D data map that should be displayed on top of meanA. This is what your VectorMaps corresponds to.

Now, to signed distances. The way MeshMath calculates the sign of the distances (all distances are by definition positive) is calculating if the distances are coming out or into the reference mesh (meanA). MeshMath uses the normal vectors of meanA ([url=https://en.wikipedia.org/wiki/Normal_(geometry)]https://en.wikipedia.org/wiki/Normal_(geometry)[/url]). If the geometry of meanA is right, normal vectors should be pointing outwards the shape in each of its triangles. So we compare our difference vectors with the normal vectors of meanA and if they match the distance will be positive (both pointing outwards) if they don't the distance will be negative (diff vector points inwards, normal points outwards).
For the example above, the signed distances are (figure 3):

Figure 3: https://drive.google.com/open?id=0B06eo8efbhotX3pKMV9YQjUwRjQ

Where blue is positive and red is negative. Now compare with the first picture. Areas in which meanB (red) is bigger than meanA (green) have positive sigdistances. Areas in which meanB is smaller than meanA have negative distances. This is what DiffMagnitude should be showing in your case.

Now, for how VectorMaps and DiffMagnitude look like, of course they should look different, they are different things: VectorMaps are 3D maps, DiffMagnitude are 1D maps. In order to understand your problem a little better, could you please tell me what program are you using to display them?

I hope all the information above makes sense. Let me know if it doesn't, I am happy to clarify.
Thanks,


Beatriz