The design is commonly known as a floor length women's transformer maxi dress or ladies infinity gown
If it's good enough for Bottega Veneta, Celine, Prada and Acne Studios, it's good enough for a long weekend in a field, and if designer brands aren't inspiration enough, you can take inspo from the outfits Glamour editors and contributors are planning to wear below Inspiration is great, but realistically your festival clothes while expressive, fun, and something that adequately conveys your excitement around attending the event should also be something you feel comfortable in (as well as being suited for the climate and conditions)
In the past few years, white dress pants have really picked up much popularity
Slingback heels or pointed-toe mules keep the look elegant and feminine
They were using those plastic bins to hold their clothes
But hey, if you are looking for that red dress inspiration for your reception look, then you might have to pin this down