Fix deprecated mesh conversion

[nikitalita]

In #60309, when octahedral mesh conversion was added to Godot 4.x, the src_offset increment were modified erroneously and changed the increment value.

https://github.com/godotengine/godot/pull/60309/files#r1017101020
https://github.com/godotengine/godot/pull/60309/files#r1017104192

This restores the previous offset values and adds clarifying comments where necessary.

[nikitalita]

re: @clayjohn @The-O-King

[clayjohn]

Looks mostly good, only non-compressed non-octahedral tangents needs to be updated.

I left a comment on each line to show which entry from 3.x it matches for future reference.

Once the non-compressed non-octahedral tangent code is fixed this should be good to merge

[clayjohn]

The code looks great! The final step before merging is to squash all the commits together so that the whole PR only contains 1 big commit with all your changes. We like to merge one commit at a time to keep the git history clean and navigable.

If you don't know how to do that, we have a helpful tutorial in the official documentation https://docs.godotengine.org/en/latest/community/contributing/pr_workflow.html#the-interactive-rebase

[nikitalita]

I'm not going to be near a computer for the next week. Can you please squash and merge?

[clayjohn]

I'm not going to be near a computer for the next week. Can you please squash and merge?

Sorry, no. We don't have that enabled for this repository :(

[nikitalita]

apparently GitHub codespaces is free now and works on ipad safari, so there you go.

[akien-mga]

Thanks!