# Objective

Add examples for zooming (and orbiting) orthographic and perspective
cameras.

I'm pretty green with 3D, so please treat with suspicion! I note that
if/when #15075 is merged, `.scale` will go away so this example uses
`.scaling_mode`.

Closes #2580

---------

Co-authored-by: Alice Cecile <[email protected]>
Co-authored-by: Jan Hohenheim <[email protected]>

# Objective

Add examples for zooming (and orbiting) orthographic and perspective
cameras.

I'm pretty green with 3D, so please treat with suspicion! I note that
if/when #15075 is merged, `.scale` will go away so this example uses
`.scaling_mode`.

Closes #2580

…)"

This reverts commit f326705.

# Objective

Fixes #15791.

As raised in #11022, scaling orthographic cameras is confusing! In Bevy
0.14, there were multiple completely redundant ways to do this, and no
clear guidance on which to use.

As a result, #15075 removed the `scale` field from
`OrthographicProjection` completely, solving the redundancy issue.

However, this resulted in an unintuitive API and a painful migration, as
discussed in #15791. Users simply want to change a single parameter to
zoom, rather than deal with the irrelevant details of how the camera is
being scaled.

## Solution

This PR reverts #15075, and takes an alternate, more nuanced approach to
the redundancy problem. `ScalingMode::WindowSize` was by far the biggest
offender. This was the default variant, and stored a float that was
*fully* redundant to setting `scale`.

All of the other variants contained meaningful semantic information and
had an intuitive scale. I could have made these unitless, storing an
aspect ratio, but this would have been a worse API and resulted in a
pointlessly painful migration.

In the course of this work I've also:

- improved the documentation to explain that you should just set `scale`
to zoom cameras
- swapped to named fields for all of the variants in `ScalingMode` for
more clarity about the parameter meanings
- substantially improved the `projection_zoom` example
- removed the footgunny `Mul` and `Div` impls for `ScalingMode`,
especially since these no longer have the intended effect on
`ScalingMode::WindowSize`.
- removed a rounding step because this is now redundant 🎉 

## Testing

I've tested these changes as part of my work in the `projection_zoom`
example, and things seem to work fine.

## Migration Guide

`ScalingMode` has been refactored for clarity, especially on how to zoom
orthographic cameras and their projections:

- `ScalingMode::WindowSize` no longer stores a float, and acts as if its
value was 1. Divide your camera's scale by any previous value to achieve
identical results.
- `ScalingMode::FixedVertical` and `FixedHorizontal` now use named
fields.

---------

Co-authored-by: MiniaczQ <[email protected]>