I'm working on a web application with Material Design.
I have some dialogs in this application, and I'm wondering if it's more conventional to have a close cross or not.
This is not a fullscreen dialog, so user can click outside to close, or click on the cancel button (here without).
In my mind this is not mandatory, and even not recommended for non fullscreen dialogs.
This is a great question and its opens up a question back to you. Why are you using a modal?
I really like how Atlassian considers this UI pattern.
Use modal dialogs when you need a user response, to reveal critical information, or to show info without losing the overall context of a page. No other interactions on the main page can be accessed while a modal dialog is active. Modal dialogs are invasive to the user's workflow as they appear above all other content. Their usage is quite powerful, as it focuses the user on a single task. -- Atlassian Design System - Modals.
^ that being said, the answer is wether your showing critical information than yes you should provide a "x", If you require critical user response then no you would not use an "x".
Interesting question. For what I see on your design. You need the user to take action and choose either WITH or WITHOUT.
If you are showing a close cross, perhaps the action to take is not that important and you might not need to display a modal in the first place.
