I had begun to see the people rushing by outside in the mall’s concourse as a river of humanity.
参考译文：我开始看着在商场外面大厅里来来往往的人们，如同形成了一条“人河/人潮”。
【1】by副词，表示 经过, 修饰动词rush
【2】outside副词，表示 在外面 修饰介词短语，商场外面的大厅。
【3】in the mall’s concourse 为介词短语走地点状语“在商场大厅里”
以上句子整体语法框架结构为“主语+谓语动词+宾语” 结构
I 【主语】//had begun【谓语动词】// to see the people rushing by outside in the mall’s concourse as a river of humanity【宾语】//.
备注(1)：不定式to see里还有一个现在分词作宾补 即 to see sb doing sth看见某人正在做某事，as a river of humanity为介词短语做状语。as为介词用法，意思“像/如同”
They were all dressed as clowns.他们都打扮像小丑。
The bomb was disguised as a package.炸弹伪装成像一个包裹。
备注(2)：see sb+后置定语+as a river of humanity. 把...看作为“人河/人潮” 结构 see sb as +名词。as为介词短语作宾补。
有人可能会按照第2种结构进行理解。实际上不能按照第2种结构进行理解。因为句中see为“看见”，不是“看作/认为”
see +名词(A) +as 名词(B) 认为A 是B; 把A看作为B ，第2种结构陈述“说话人观点和看法”
His colleagues see him as a future director.他的同事认为他很可能是未来的负责人
She saw him as a visionary, but her father saw him as a man who couldn't make a living.
她认为他是一个有眼光的人，但是她父亲却认为他没有谋生的能力。
They have a normal body weight but see themselves as being fat.
他们体重正常，但自认为偏胖。
