Spine-Unity 3.8.99 Json parse

nnton3

Hi everyone!
I’m using a Path in Spine and I need to parse its data in Unity. Some of the values look a bit strange to me.

For example, for an open Path:

From pathAttachment I get the number of coordinates as points * 6 — that part makes sense.

But in lengths, the number of segments is equal to the number of points, even though for an open path I’d expect it to be points - 1.

What does this last length represent, and how should I use it to correctly display the Path?

Spinebot

The lengths array in a PathAttachment represents the lengths of each Bezier curve segment that makes up the path. For an open path, the number of segments should indeed be points - 1, as each segment connects two points. However, the lengths array may include an additional entry to account for the total length of the path or for internal calculations. This extra length can be used for operations like path constraints, where the entire path length is needed for calculations. To correctly display the path, you should focus on the segments between the points and use the lengths array to understand the distribution of these segments along the path.

nnton3

Spinebot I’m working with the total path length, and I need to understand how to use this value, because right now I don’t know how to handle this case. If I use points - 1, the line is not drawn completely. If I also include the last segment, the line becomes longer than it should be.

Is the last entry in the lengths array actually the total length of the path, and should I only use it when I need the full path length (for example, with path constraints), while for rendering I should stick to the first points - 1 segments?

Harald

It's best to always have a look at what the source code actually does to evaluate positions, e.g. here:
EsotericSoftware/spine-runtimesblob/3.8/spine-csharp/src/PathConstraint.cs#L193
EsotericSoftware/spine-runtimesblob/3.8/spine-csharp/src/PathConstraint.cs#L318C35-L318C42
If something is unclear, you could always export the skeleton in question and play an animation that uses e.g. the path constraint, then set breakpoints at the respective code parts to see how values are evaluated. Then you can compare whether your implementation does something different.