Hey Hey. Are you running version r276, the latest stable release?
There is an example called "Foggy Outbreak". Just search "foggy" on the start page and it will come right up. You might find checking out the Event Sheet in the example helpful.
It basically "Requests pointer lock", if the mouse does not have "pointer lock" yet, and that Action is within an "On any click" Event using the Mouse Object.
As far as, placing a sprite/object at the center of the screen within the 3D Game. Take a look at the "GunOverlay" group within the Event Sheet in that example to get a general idea on where to begin with that aspect.
The built in examples of Construct are extremely helpful. You can learn a lot just by deconstructing the Event Sheets within them, and figuring out how different game mechanics have been created in the examples provided.
Thank you for helping me ! Sadly this is not my issue :(
I have a hard time explaining it : I wish to position an object in the 3d layer at the exact position where the camera is pointing at. So basically I could use mouse.xy but the pointer doesnt automatically lock with the pointer at center of the screen :
Here I want my red square to be positioned at all time at the center of my screen instead of only the cursor. If i lock my cursor it will follow it but it won't be at the center.