Direct Opposites:
* Ignore: To completely disregard or not think about something.
* Overlook: To fail to notice or consider something.
* Disregard: To pay no attention to something.
More nuanced antonyms:
* Misunderstand: To interpret something incorrectly.
* Misinterpret: To understand something in a way that is not intended.
* Dismiss: To reject or ignore an idea or suggestion.
* Neglect: To fail to pay attention to something.
The best antonym for "envision" will depend on the specific context of your sentence.