UPDATE: check out the latest version here!! blendermarket.com/products/nview-v3

What does nView do?

nView is a Blender add-on for optimizing scenes based on what can be seen by the camera. It improves viewport speed and saves rendering time without compromising anything visually.

Select only the visible objects!
Automatically hide and disable collections or objects that reduce your performance, without affecting what's seen by the camera!
Bake the objects' visibility to keyframes, accelerating viewport playback and render times!

nView Operators

Here's a quick rundown of the operators:

Select Object nView - if the object is visible, select it!
Set Object nView - if the object is visible, set its visibility attributes (selectable, visible, viewport or render)
Set Collection nView - if any of the viable objects in a collection is visible, set its collection's visibility attributes (view layer, visible, viewport, render, holdout, or indirect).
Set Mask nView - if the object is partially visible, generate a vertex group and mask modifier to only show visible faces.
Select Mesh nView (mesh edit mode) - if the vertex/edge/face is in visible, select it!
Hide Mesh nView (mesh edit mode) - if the vertex/edge/face is visible, show it! The rest are hidden (this does not affect render visibility, just for the viewport in mesh edit mode)
Reset nView - utility operator to reveal all collections and objects (in case you want to clear all that you've done)

Animation

Distinguished Features

Supports any render engine
Filter based on current selection, visibility, and instanced collections
Supports all object types - not just meshes - including instanced collections!
Include objects indirectly visible to the camera in reflections!

For more on these and individual settings, watch the following:

Releases

October 2021 (1.2.1) - initial release to Blender Market!
October 2021-2 (1.3.1) - n-bounces and a bugfix (selected objects filter was ignored in some cases)
October 2021-3 (1.3.4) - invert selection, bugfixes, minor performance improvement
November 2021 (1.5.0) - improved view frustum algorithm, added input for bounce distance, removed input for using scene resolution for occlusion
Thanksgiving 2021 (2.0.0) - animation support: select or hide objects over a given frame range, as well as the option to keyframe object visibility. Also, cleaned up a UI a little
December 2021 (2.1.1) - margin setting for view frustum algorithm, and a fix for non-mesh objects with occlusion algorithm
January 2022 (2.1.6) - mesh nView (similar functionality in mesh edit mode) with backface algorithm, dramatically optimized auto keyframing, operator to clear object visibility keyframes (to conveniently revert auto keyframing, if needed), bug fixes with camera positions
February 2022 (2.1.7) - bug fixes related to collection instancing, as well as a new option to exclude instanced objects from calculations
June 2022 (2.1.9) - bug fix with panel and deprecated hair object in 3.2, testing validated for Blender 3.2!
October 2022 (2.1.10) - bug fix when an object's instanced collection property is empty
December 2022 (2.2.0) - behavior change, matching user expectations: for animations, instead of using only the active camera only from first frame of the frame range, active camera is retrieved per frame. Allows for camera changes in an animation.
Winter Holiday 2022 (2.3.2) - operator redo panels now contain nearly all the nView settings, allow you to quickly tweak after the fact (the only exceptions are object type and camera - due to API limitations, they must be set before running the operator). Lower default animation frame step (10 to 5), and two bugs squashed with the "Select Mesh nView" operator: the selected objects only and extend selection parameters now work as expected.
January 2023 (2.3.5) - added operators to reset visibility for objects and collections - undo does work for nView, but in the rare case you've gone too far, these are available. The extend and invert selection properties are now exposed on the panels to tweak before running. For the auto animated keyframe option, frames where the active camera changes are always considered, even if the frame step size skips it. That way, you can keep the frame step high without worrying about missing those active camera changes.
February 2023 (2.3.7) - code refactoring, improving import usage to speed up add-on registration.
April 2023 (2.3.9) - Added a toggle for optimized object occlusion tests. While it restricts the supported object types, it gives a consistent 30% speed increase. Some toggles are now hidden as expected when auto keyframe is enabled. Improved automated testing for safer deployments.
May 2023 (2.3.10) - A bug fix for an edge case when the object is scaled to zero on all axes.
June 2023 (2.3.11) - bug fix for when the occlusion method detects instancing empties without a collection selected.