In recent conversations with *Valedhelven, we've discussed a possible follow-up to her famous Pegicornitauress as one in which such a mother is nursing her baby, while in back of her we see her immediate family coming down with gifts for the newborn: in particular, a rainbow, freshly picked.

If so, then surely the rainbow (primary, to be more specific) will be somewhat deformed, and at a non-standard camera angle; therefore we need a 3D model thereof.

I am in the process of constructing such a model, and documenting how I did it.
Thus far I have Part 1: texture (in two variants) free to download.