The air is so still that the smoke is rising straight up from the fire.空气静止不动,烟从火上垂直升起.so在这里是做什么的?表语可以两个形容词相连吗?rising straight同是形容词,为什么rising在前straight在后啊?

Still Air (poem)
Today I felt like I was in a film
I was on my way home
Walking down the road
My thick coat unbuttoned
And the hooded brown velvet top I wear underneath
Zipped straight down to the bottom.
The air was mellow
A freak aberration for an early February night.
There was an unexpected feeling of the winter being cut short,
And all that is good about the spring was to begin.
I passed a bus stop
And as I turned to look for a bus
A cheeky gust of air peeled back my layers up and away from my body!
For an instant I felt like I was in a film
Like James Dean hitching a ride in Down Town New York City
Cinematography so delicious!
I laughed at the air
And February抯 joke.
And kept the memory like a good book.

你的句子理解要多学下.
so是副词,still是形容词,rising是进行时的现在分词,straight修饰rising.

so...that构成固定句式为“太...以至于...” still在这里为形容词 静止的,不动的,静寂的
straight up是副词翻译为垂直