This node can be used to measure the distance along a surface (aka the geodesic distance), which is useful for doing masking operations based on distance. It assigns to each point its distance to the point in the source group that is closest to it geodesically. Exact computation of distances along polygonal surfaces is computationally expensive. This node uses a method based on the heat diffusion to approximate these distances with often high accuracy. In addition, it allows for a natural smoothing of the computed distance field which, if calculated in full accuracy, may have cusps and sharp changes which could be undesirable for some use cases.

Points that are not reachable from any of the points in the source group will be assigned a distance of -1.

• This method only works for distances along manifold surfaces, meaning distances cannot be tracked across non-manifold edges or points. So, non-manifold edges and points are interpreted as though being cut away from the surface, leaving narrow slits or tiny holes in their places.

• This node is similar in function to Distance along Geometry which also approximates geodesic distances. It is expected to be considerably slower than Distance along Geometry, particularly if it is used only once (see the next tip) but it is more accurate and can handle complicated polygonal shapes better.

• This node is particularly useful and efficient if the source points are needed to be modified frequently, e.g. in a loop network. It maintains a cache that allows it, upon modification to the source group, to recompute the distance field very quickly and with the same accuracy.

• On very large meshes, the heat diffusion method may fail numerically, in which case it is possible that the results for points at a certain distance value or higher to be calculated incorrectly. In such cases, adding a little bit of smoothing can often resolve the issue.