When snapping, be it during normal modeling or when retopoing a sculpt, it
would be very nice to only snap to mesh elements which normal face the camera.
The check for snapping would go something like this:
- Get the normal of the snapping candidate
- Calculate the vector from the camera to the center of the element in question (we will call this the camera vector)
- Create the dot product of the camera vector and the normal
- If the dot product is positive, that means that the element is back facing and should be excluded from snapping
This option will be available as a checkbox in the snapping drop down menu.
Perhaps this option should also be on automatically when backface culling is turned on.